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Title 30 – Mineral Resources–Volume 1

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Title 30 – Mineral Resources–Volume 1


Part


chapter i – Mine Safety and Health Administration, Department of Labor

1

CHAPTER I – MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR

SUBCHAPTER A – OFFICIAL EMBLEM AND OMB CONTROL NUMBERS FOR RECORDKEEPING AND REPORTING

PART 1 – MINE SAFETY AND HEALTH ADMINISTRATION; ESTABLISHMENT AND USE OF OFFICIAL EMBLEM


Authority:Sec. 508, Federal Coal Mine Health and Safety Act of 1969; sec. 301 of Title 5, United States Code; secs. 301(a) and 302(a), Federal Mine Safety and Health Amendments Act of 1977, Pub. L. 95-164, 30 U.S.C. 961 and 951 and 29 U.S.C. 577a, 91 Stat. 1317 and 91 Stat. 1319; sec. 508, Federal Mine Safety and Health Act of 1977, Pub. L. 91-173 as amended by Pub. L. 95-164, 30 U.S.C. 957, 83 Stat. 803.


Source:39 FR 23997, June 28, 1974, unless otherwise noted.

§ 1.1 Official emblem.

The following emblem is established and shall be used as the official emblem of the Mine Safety and Health Administration, except where use of the Departmental Seal is required:



[39 FR 23997, June 28, 1974, as amended at 43 FR 12312, Mar. 24, 1978]


§ 1.2 Description.

The emblem of the Mine Safety and Health Administration is of contemporary design with the letters and acronym of the Administration delineated as MSHA appearing in large letters in the middle of the emblem. Above the letters and acronym appear the words “United States Department of Labor” and below the letters and acronym appear the words “Mine Safety and Health Administration.”


[39 FR 23997, June 28, 1974, as amended at 43 FR 12312, Mar. 24, 1978]


§ 1.3 Use of letters and acronym MSHA.

The letters and acronym MSHA may be used and substituted for the words “Mine Safety and Health Administration” in correspondence, rules, regulations, and in certificates of approval, approval plates, labels, and markings prescribed by the Mine Safety and Health Administration to designate and denote equipment, devices, and apparatus approved as “permissible” and suitable for use in mines under the applicable parts of Chapter I of this title, and in such other documents, publications, and pamphlets, and on signs, clothing and uniforms, and offices of the Administration and at such times and locations as may be deemed appropriate by the Assistant Secretary of Labor for Mine Safety and Health.


[39 FR 23997, June 28, 1974, as amended at 43 FR 12312, Mar. 24, 1978]


PART 3 – OMB CONTROL NUMBERS UNDER THE PAPERWORK REDUCTION ACT


Authority:30 U.S.C. 957; 44 U.S.C. 3501-3520.

§ 3.1 OMB control numbers.

The collection of information requirements in MSHA regulation sections in this chapter have been approved and assigned control numbers by the Office of Management and Budget (OMB) under the Paperwork Reduction Act. Regulation sections in this chapter containing paperwork requirements and their respective OMB control numbers are displayed in the following table:


Table 1 – OMB Control Numbers

30 CFR Citation
OMB Control No.
Subchapter B – Testing, Evaluation, and Approval of Mining Products
6.101219-0066
7.31219-0066
7.41219-0066
7.61219-0066
7.71219-0066
7.231219-0066
7.271219-0066
7.281219-0066
7.291219-0066
7.301219-0066
7.431219-0066
7.461219-0066
7.471219-0066
7.481219-0066
7.491219-0066
7.511219-0066
7.631219-0066
7.691219-0066
7.711219-0066
7.831219-0066
7.901219-0066
7.971219-0066
7.1051219-0066
7.1081219-0066
7.3031219-0066
7.3061219-0066
7.3091219-0066
7.3111219-0066
7.4031219-0066
7.4071219-0066
7.4081219-0066
7.4091219-0066
7.4111219-0066
15.41219-0066
15.81219-0066
18.61219-0066
18.151219-0066
18.531219-0066, -0116
18.811219-0066
18.821219-0066
18.931219-0066
18.941219-0066
19.31219-0066
19.131219-0066
20.31219-0066
20.141219-0066
22.41219-0066
22.81219-0066
22.111219-0066
23.31219-0066
23.71219-0066
23.101219-0066
23.121219-0066
23.141219-0066
27.41219-0066
27.61219-0066
27.111219-0066
28.101219-0066
28.231219-0066
28.251219-0066
28.301219-0066
28.311219-0066
33.61219-0066
33.121219-0066
35.61219-0066
35.101219-0066
35.121219-0066
36.61219-0066
36.121219-0066
Subchapter G – Filing and Other Administrative Requirements
40.31219-0042
40.41219-0042
40.51219-0042
41.201219-0042
43.41219-0014
43.71219-0014
44.91219-0065
44.101219-0065
44.111219-0065
45.31219-0040
45.41219-0040
Subchapter H – Education and Training
46.31219-0131
46.51219-0131
46.61219-0131
46.71219-0131
46.81219-0131
46.91219-0131
46.111219-0131
47.311219-0133
47.321219-0133
47.32(a)(4)1219-0133
47.411219-0133
47.511219-0133
47.711219-0133
47.731219-0133
48.31219-0009, -0141
48.91219-0009
48.231219-0009
48.291219-0009
49.21219-0078
49.31219-0078
49.41219-0078
49.61219-0078
49.71219-0078
49.81219-0078
49.91219-0078
49.121219-0144
49.161219-0144
49.181219-0144
49.501219-0144
Subchapter I – Accidents, Injuries, Illnesses, Employment, and Production in Mines
50.101219-0007, -0141
50.111219-0007, -0141
50.201219-0007
50.301219-0007
Subchapter K – Metal and Nonmetal Mine Safety and Health
56.10001219-0042
56.3203(a)1219-0121
56.50051219-0048
56.130151219-0089
56.130301219-0089
56.141001219-0089
56.180021219-0089
56.190221219-0034
56.190231219-0034
56.190571219-0049
56.191211219-0034
57.10001219-0042
57.3203(a)1219-0121
57.34611219-0097
57.50051219-0048
57.50371219-0003
57.50401219-0003
57.50471219-0039
57.50601219-0135
57.50651219-0135
57.50661219-0135
57.50671219-0135
57.50701219-0135
57.50711219-0135
57.50751219-0135
57.85201219-0016
57.85251219-0016
57.110531219-0046
57.130151219-0089
57.130301219-0089
57.141001219-0089
57.180021219-0089
57.190221219-0034
57.190231219-0034
57.190571219-0049
57.191211219-0034
57.22004(c)1219-0103
57.222041219-0030
57.222291219-0103
57.222301219-0103
57.222311219-0103
57.222391219-0103
57.224011219-0096
57.226061219-0095
Subchapter M – Uniform Mine Health Regulations
62.1101219-0120
62.1301219-0120
62.1701219-0120
62.1711219-0120
62.1721219-0120
62.1731219-0120
62.1741219-0120
62.1751219-0120
62.1801219-0120
62.1901219-0120
Subchapter O – Coal Mine Safety and Health
70.201(c)1219-0011
70.202(b)1219-0011
70.2041219-0011
70.2091219-0011
70.2101219-0011
70.2201219-0011
70.220(a)1219-0011
71.201(c)1219-0011
71.202(b)1219-0011
71.2041219-0011
71.2091219-0011
71.2101219-0011
71.2201219-0011
71.220(a)1219-0011
71.3001219-0011
71.3011219-0011
71.301(d)1219-0011
71.4031219-0024
71.4041219-0024
72.5001219-0124
72.5031219-0124
72.5101219-0124
72.5201219-0124
75.1001219-0127
75.153(a)(2)1219-0001
75.1551219-0127
75.1591219-0127
75.1601219-0127
75.1611219-0127
75.204(a)1219-0121
75.2151219-0004
75.2201219-0004
75.2211219-0004
75.2221219-0004
75.2231219-0004
75.3101219-0088
75.3121219-0088
75.3351219-0142
75.3361219-0142
75.3371219-0142
75.3381219-0142
75.3421219-0088
75.3501219-0138
75.3511219-0088, -0116, -0138
75.3521219-0138
75.3601219-0088
75.3611219-0088
75.3621219-0088
75.3631219-0088
75.3641219-0088
75.3701219-0088
75.3711219-0088, -0138
75.3721219-0073
75.3731219-0073
75.3821219-0088
75.5121219-0116
75.7031219-0116
75.703-31219-0116
75.8001219-0116
75.800-41219-0116
75.8201210-0116
75.8211219-0116
75.9001219-0116
75.900-41219-0116
75.1001-11219-0116
75.1100-31219-0054
75.1103-81219-0054
75.1103-111219-0054
75.12001219-0073
75.1200-11219-0073
75.12011219-0073
75.12021219-0073
75.1202-11219-0073
75.12031219-0073
75.12041219-0073
75.1204-11219-0073
75.13211219-0025
75.13271219-0025
75.1400-21219-0034
75.1400-41219-0034
75.14321219-0034
75.14331219-0034
75.15011219-0054
75.15021219-0054, -0141
75.15041219-0141
75.15051219-0141
75.17021219-0041
75.1712-41219-0024
75.1712-51219-0024
75.1713-11219-0078
75.1714-31219-0141
75.1714-3(e)1219-0044
75.1714-41219-0044
75.1714-51219-0141
75.1714-81219-0141
75.17161219-0020
75.1716-11219-0020
75.1716-31219-0020
75.17211219-0073
75.19011219-0119
75.19041219-0119
75.19111219-0119
75.19121219-0119
75.19141219-0119
75.19151219-0119, -0124
77.1001219-0127
77.103(a)(2)1219-0001
77.1051219-0127
77.1061219-0127
77.1071219-0127
77.107-11219-0127
77.2151219-0015
77.215-21219-0015
77.215-31219-0015
77.215-41219-0015
77.216-21219-0015
77.216-31219-0015
77.216-41219-0015
77.216-51219-0015
77.5021219-0116
77.8001219-0116
77.800-21219-0116
77.9001219-0116
77.900-21219-0116
77.10001219-0026
77.1000-11219-0026
77.11011219-0051
77.12001219-0073
77.12011219-0073
77.12021219-0073
77.14041219-0034
77.14321219-0034
77.14331219-0034
77.17021219-0078
77.17131219-0083
77.19001219-0019
77.19011219-0082
77.19061219-0034
77.1909-11219-0025
90.201(c)1219-0011
90.202(b)1219-0011
90.2041219-0011
90.2091219-0011
90.2201219-0011
90.3001219-0011
90.3011219-0011
90.301(d)1219-0011

[73 FR 36790, June 30, 2008]


SUBCHAPTER B – TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS

PART 5 – FEES FOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS


Authority:30 U.S.C. 957.



Source:80 FR 45056, July 29, 2015, unless otherwise noted.

§ 5.10 Purpose and scope.

This part establishes a system under which MSHA charges a fee for services provided. This part includes the management and calculation of fees for the approval program, which includes: Application processing, testing and evaluation, approval decisions, post-approval activities, and termination of approvals.


§ 5.30 Fee calculation.

(a) Fee calculation. MSHA charges a fee based on an hourly rate for Approval and Certification Center (A&CC) approval program activities and other associated costs, such as travel expenses and part 15 fees. Part 15 fees for services provided to MSHA by other organizations may be set by those organizations.


(b) Hourly rate calculation. The hourly rate consists of direct and indirect costs of the A&CC’s approval program divided by the number of direct hours worked on all approval program activities.


(1) Direct costs are compensation and benefit costs for hours worked on approval program activities.


(2) Indirect costs are a proportionate share of the following A&CC costs:


(i) Compensation and benefit hours worked in support of all A&CC activities;


(ii) A&CC building and equipment depreciation costs;


(iii) A&CC utilities, facility and equipment maintenance, and supplies and materials; and


(iv) Information Technology and other services the Department of Labor provides to the A&CC.


(c) Fees are charged for


(1) Application processing (e.g., administrative and technical review of applications, computer tracking, and status reporting);


(2) Testing and evaluation (e.g., analysis of drawings, technical evaluation, testing, test set up and test tear down, and internal quality control activities);


(3) Approval decisions (e.g., consultation on applications, records control and security, document preparation); and


(4) Two post-approval activities: changes to approvals and post-approval product audits.


(d) Fees are not charged for


(1) Technical assistance not related to processing an approval application;


(2) Technical programs, including development of new technology programs;


(3) Participation in research conducted by other government agencies or private organizations; and


(4) Regulatory review activities, including participation in the development of health and safety standards, regulations, and legislation.


(e) Fee estimate. Except as provided in paragraphs (e)(1) and (2) of this section, on completion of an initial administrative review of the application, the A&CC will prepare a maximum fee estimate for each application. A&CC will begin the technical evaluation after the applicant authorizes the fee estimate.


(1) The applicant may pre-authorize an expenditure for services, and may further choose to pre-authorize either a maximum dollar amount or an expenditure without a specified maximum amount.


(i) All applications containing a pre-authorization statement will be put in the queue for the technical evaluation on completion of an initial administrative review.


(ii) MSHA will concurrently prepare a maximum fee estimate for applications containing a statement pre-authorizing a maximum dollar amount, and will provide the applicant with this estimate.


(2) Where MSHA’s estimated maximum fee exceeds the pre-authorized maximum dollar amount, the applicant has the choice of cancelling the action and paying for all work done up to the time of the cancellation, or authorizing MSHA’s estimate.


(3) Under the Revised Acceptance Modification Program (RAMP), MSHA expedites applications for acceptance of minor changes to previously approved, certified, accepted, or evaluated products. The applicant must pre-authorize a fixed dollar amount, set by MSHA, for processing the application.


(f) If unforeseen circumstances are discovered during the evaluation, and MSHA determines that these circumstances would result in the actual costs exceeding either the pre-authorized expenditure or the authorized maximum fee estimate, as appropriate, MSHA will prepare a revised maximum fee estimate for completing the evaluation. The applicant will have the option of either cancelling the action and paying for services rendered or authorizing MSHA’s revised estimate, in which case MSHA will continue to test and evaluate the product.


(g) If the actual cost of processing the application is less than MSHA’s maximum fee estimate, MSHA will charge the actual cost.


§ 5.40 Fee administration.

Applicants and approval holders will be billed for all fees, including actual travel expenses, if any, when approval program activities are completed. Invoices will contain specific payment instruction, including the address to mail payments and authorized methods of payment.


§ 5.50 Fee revisions.

The hourly rate will remain in effect for at least one year and be subject to revision at least once every three years.


PART 6 – TESTING AND EVALUATION BY INDEPENDENT LABORATORIES AND NON-MSHA PRODUCT SAFETY STANDARDS


Authority:30 U.S.C. 957.


Source:68 FR 36417, June 17, 2003, unless otherwise noted.

§ 6.1 Purpose and effective date.

This part sets out alternate requirements for testing and evaluation of products MSHA approves for use in gassy underground mines. It permits manufacturers of certain products who seek MSHA approval to use an independent laboratory to perform, in whole or part, the necessary testing and evaluation for approval. It also permits manufacturers to have their products approved based on non-MSHA product safety standards once MSHA has determined that the non-MSHA standards are equivalent to MSHA’s applicable product approval requirements or can be modified to provide at least the same degree of protection as those MSHA requirements. The provisions of this part may be used by applicants for product approval under parts 18, 19, 20, 22, 23, 27, 33, 35, and 36. This rule is effective August 18, 2003.


§ 6.2 Definitions.

The following definitions apply in this part.


Applicant. An individual or organization that manufactures or controls the assembly of a product and applies to MSHA for approval of that product.


Approval. A written document issued by MSHA which states that a product has met the applicable requirements of part 18, 19, 20, 22, 23, 27, 33, 35, or 36. The definition is based on the existing definitions of “approval” in the parts specified above. It is expanded to include “certification” and “acceptance” because these terms also are used to denote MSHA approval.


Approval holder. An applicant whose application for approval of a product under part 18, 19, 20, 22, 23, 27, 33, 35 or 36 of this chapter has been approved by MSHA.


Equivalent non-MSHA product safety standards. A non-MSHA product safety standard, or group of standards, determined by MSHA to provide at least the same degree of protection as the applicable MSHA product approval requirements in parts 14, 18, 19, 20, 22, 23, 27, 33, 35, and 36, or which in modified form provide at least the same degree of protection.


Independent laboratory. A laboratory that:


(1) has been recognized by a laboratory accrediting organization to test and evaluate products to a product safety standard, and


(2) is free from commercial, financial, and other pressures that may influence the results of the testing and evaluation process.


Post-approval product audit. The examination, testing, or both, by MSHA of approved products selected by MSHA to determine whether those products meet the applicable product approval requirements and have been manufactured as approved.


Product safety standard. A document, or group of documents, that specifies the requirements for the testing and evaluation of a product for use in explosive gas and dust atmospheres, and, when appropriate, includes documents addressing the flammability properties of products.


[68 FR 36417, June 17, 2003, as amended at 73 FR 80609, Dec. 31, 2008]


§ 6.10 Use of independent laboratories.

(a) MSHA will accept testing and evaluation performed by an independent laboratory for purposes of MSHA product approval provided that MSHA receives as part of the application:


(1) Written evidence of the laboratory’s independence and current recognition by a laboratory accrediting organization;


(2) Complete technical explanation of how the product complies with each requirement in the applicable MSHA product approval requirements;


(3) Identification of components or features of the product that are critical to the safety of the product; and


(4) All documentation, including drawings and specifications, as submitted to the independent laboratory by the applicant and as required by the applicable part under this chapter.


(b) Product testing and evaluation performed by independent laboratories for purposes of MSHA approval must comply with the applicable MSHA product approval requirements.


(c) Product testing and evaluation must be conducted or witnessed by the laboratory’s personnel.


(d) After review of the information required under paragraphs (a)(1) through (a)(4) of this section, MSHA will notify the applicant if additional information or testing is required. The applicant must provide this information, arrange any additional or repeat tests and notify MSHA of the location, date, and time of the test(s). MSHA may observe any additional testing conducted by an independent laboratory. Further, MSHA may decide to conduct the additional or repeated tests at the applicant’s expense. The applicant must supply any additional components necessary for testing and evaluation.


(e) Upon request by MSHA, but not more than once a year, except for cause, approval holders of products approved based on independent laboratory testing and evaluation must make such products available for post-approval audit at a mutually agreeable site at no cost to MSHA.


(f) Once the product is approved, the approval holder must notify MSHA of all product defects of which they become aware.


§ 6.20 MSHA acceptance of equivalent non-MSHA product safety standards.

(a) MSHA will accept non-MSHA product safety standards, or groups of standards, as equivalent after determining that they:


(1) Provide at least the same degree of protection as MSHA’s product approval requirements in parts 14, 18, 19, 20, 33, 35 and 36 of this chapter; or


(2) Can be modified to provide at least the same degree of protection as those MSHA requirements.


(b) MSHA will publish its intent to review any non-MSHA product safety standard for equivalency in the Federal Register for the purpose of soliciting public input.


(c) A listing of all equivalency determinations will be published in this part 6 and the applicable approval parts. The listing will state whether MSHA accepts the non-MSHA product safety standards in their original form, or whether MSHA will require modifications to demonstrate equivalency. If modifications are required, they will be provided in the listing. MSHA will notify the public of each equivalency determination and will publish a summary of the basis for its determination. MSHA will provide equivalency determination reports to the public upon request to the Approval and Certification Center.


(d) After MSHA has determined that non-MSHA product safety standards are equivalent and has notified the public of such determinations, applicants may seek MSHA product approval based on such non-MSHA product safety standards.


[68 FR 36417, June 17, 2003, as amended at 73 FR 80609, Dec. 31, 2008]


§ 6.30 MSHA listing of equivalent non-MSHA product safety standards.

MSHA evaluated the following non-MSHA product safety standards and determined that they provide at least the same degree of protection as current MSHA requirements with or without modifications as indicated:


(a) The International Electrotechnical Commission’s (IEC) standards for Electrical Apparatus for Explosive Gas Atmospheres, Part 0, General Requirements (IEC 60079-0, Fourth Edition, 2004-01) and Part 1, Electrical Apparatus for Explosive Gas Atmospheres, Flameproof Enclosures “d” (IEC 60079-1, Fifth Edition, 2003-11) must be modified in order to provide at least the same degree of protection as MSHA explosion-proof enclosure requirements included in parts 7 and 18 of this chapter. Refer to §§ 7.10(c)(1) and 18.6(a)(3)(i) for a list of the required modifications. The IEC standards may be inspected at the U.S. Department of Labor, Mine Safety and Health Administration, Electrical Safety Division, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059, and may be purchased from International Electrical Commission, Central Office 3, rue de Varembé, P.O. Box 131, CH-1211 GENEVA 20, Switzerland.


(b) [Reserved]


[71 FR 28583, May 17, 2006, as amended at 73 FR 52210, Sept. 9, 2008]


PART 7 – TESTING BY APPLICANT OR THIRD PARTY


Authority:30 U.S.C. 957.


Source:53 FR 23500, June 22, 1988, unless otherwise noted.

Subpart A – General

§ 7.1 Purpose and scope.

This part sets out requirements for MSHA approval of certain equipment and materials for use in underground mines whose product testing and evaluation does not involve subjective analysis. These requirements apply to products listed in the subparts following this Subpart A. After the dates specified in the following subparts, requests for approval of products shall be made in accordance with this Subpart A and the applicable subpart.


§ 7.2 Definitions.

The following definitions apply in this part.


Applicant. An individual or organization that manufactures or controls the assembly of a product and that applies to MSHA for approval of that product.


Approval. A document issued by MSHA which states that a product has met the requirements of this part and which authorizes an approval marking identifying the product as approved.


Authorized company official. An individual designated by applicant who has the authority to bind the company.


Critical characteristic. A feature of a product that, if not manufactured as approved, could have a direct adverse effect on safety and for which testing or inspection is required prior to shipment to ensure conformity with the technical requirements under which the approval was issued.


Equivalent non-MSHA product safety standards. A non-MSHA product safety standard, or group of standards, that is determined by MSHA to provide at least the same degree of protection as the applicable MSHA product technical requirements in the subparts of this part, or can be modified to provide at least the same degree of protection as those MSHA requirements.


Extension of approval. A document issued by MSHA which states that the change to a product previously approved by MSHA under this part meets the requirements of this part and which authorizes the continued use of the approval marking after the appropriate extension number has been added.


Post-approval product audit. Examination, testing, or both, by MSHA of approved products selected by MSHA to determine whether those products meet the applicable technical requirements and have been manufactured as approved.


Technical requirements. The design and performance requirements for a product, as specified in a subpart of this part.


Test procedures. The methods specified in a subpart of this part used to determine whether a product meet the performance portion of the technical requirements.


[53 FR 23500, June 22, 1988; 53 FR 25569, July 7, 1988, as amended at 68 FR 36418, June 17, 2003]


§ 7.3 Application procedures and requirements.

(a) Application. Requests for an approval or extension of approval shall be sent to: U.S. Department of Labor, Mine Safety and Health Administration, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059.


(b) Fees. Fees calculated in accordance with part 5 of this title shall be submitted in accordance with § 5.40.


(c) Original approval. Each application for approval of a product shall include –


(1) A brief description of the product;


(2) The documentation specified in the appropriate subpart of this part;


(3) The name, address, and telephone number of the applicant’s representative responsible for answering any questions regarding the application;


(4) If appropriate, a statement indicating whether, in the applicant’s opinion, testing is required. If testing is not proposed, the applicant shall explain the reasons for not testing; and


(5) If appropriate, the place and date for product testing.


(d) Subsequent approval of a similar product. Each application for a product similar to one for which the applicant already holds an approval shall include –


(1) The approval number for the product which most closely resembles the new one;


(2) The information specified in paragraph (c) of this section for the new product, except that any document which is the same as one listed by MSHA in prior approvals need not be submitted, but shall be noted in the application;


(3) An explanation of any change from the existing approval; and


(4) A statement as to whether, in the applicant’s opinion, the change requires product testing. If testing is not proposed, the applicant shall explain the reasons for not testing.


(e) Extension of an approval. Any change in the approved product from the documentation on file at MSHA that affects the technical requirements of this part shall be submitted to MSHA for approval prior to implementing the change. Each application for an extension of approval shall include –


(1) The MSHA-assigned approval number for the product for which the extension is sought;


(2) A brief description of the proposed change to the previously approved product;


(3) Drawings and specifications which show the change in detail;


(4) A statement as to whether, in the applicant’s opinion, the change requires product testing. If testing is not proposed, the applicant shall explain the reasons for not testing;


(5) The place and date for product testing, if testing will be conducted; and


(6) The name, address, and telephone number of the applicant’s representative responsible for answering any questions regarding the application.


(f) Certification statement. (1) Each application for original approval, subsequent approval, or extension of approval of a product shall include a certification by the applicant that the product meets the design portion of the technical requirements, as specified in the appropriate subpart, and that the applicant will perform the quality assurance functions specified in § 7.7. For a subsequent approval or extension of approval, the applicant shall also certify that the proposed change cited in the application is the only change that affects the technical requirements.


(2) After completion of the required product testing, the applicant shall certify that the product has been tested and meets the performance portion of the technical requirements, as specified in the appropriate subpart.


(3) All certification statements shall be signed by an authorized company official.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33722, June 29, 1995; 73 FR 52210, Sept. 9, 2008]


§ 7.4 Product testing.

(a) All products submitted for approval under this part shall be tested using the test procedures specified in the appropriate subpart unless MSHA determines, upon review of the documentation submitted, that testing is not required. Applicants shall maintain records of test results and procedures for three years.


(b) Unless otherwise specified in the subpart, test instruments shall be calibrated at least as frequently as, and according to, the instrument manufacturer’s specifications, using calibration standards traceable to those set by the National Bureau of Standards, U.S. Department of Commerce or other nationally recognized standards and accurate to at least one significant figure beyond the desired accuracy.


(c) When MSHA elects to observe product testing, the applicant shall permit an MSHA official to be present at a mutually agreeable date, time, and place.


(d) MSHA will accept product testing conducted outside the United States where such acceptance is specifically required by international agreement.


[53 FR 23500, June 22, 1988; 53 FR 25569, July 7, 1988; 60 FR 33722, June 29, 1995]


§ 7.5 Issuance of approval.

(a) An applicant shall not advertise or otherwise represent a product as approved until MSHA has issued the applicant an approval.


(b) MSHA will issue an approval or a notice of the reasons for denying approval after reviewing the application, and the results of product testing, when applicable. An approval will identify the documents upon which the approval is based.


§ 7.6 Approval marking and distribution record.

(a) Each approved product shall have an approval marking, as specified in the appropriate subpart of this part.


(b) For an extension of approval, the extension number shall be added to the original approval number on the approval marking.


(c) Applicants shall maintain records of the initial sale of each unit having an approval marking. The record retention period shall be at least the expected shelf life and service life of the product.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33722, June 29, 1995]


§ 7.7 Quality assurance.

Applicants granted an approval or an extension of approval under this part shall –


(a) Inspect or test, or both, the critical characteristics in accordance with the appropriate subpart of this part;


(b) Unless otherwise specified in the subparts, calibrate instruments used for the inspection and testing of critical characteristics at least as frequently as, and according to, the instrument manufacturer’s specifications, using calibration standards traceable to those set by the National Bureau of Standards, U.S. Department of Commerce or other nationally recognized standards and use instruments accurate to at least one significant figure beyond the desired accuracy.


(c) Control production documentation so that the product is manufactured as approved;


(d) Immediately report to the MSHA Approval and Certification Center, any knowledge of a product distributed with critical characteristics not in accordance with the approval specifications.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33722, June 29, 1995]


§ 7.8 Post-approval product audit.

(a) Approved products shall be subject to periodic audits by MSHA for the purpose of determining conformity with the technical requirements upon which the approval was based. Any approved product which is to be audited shall be selected by MSHA and be representative of those distributed for use in mines. The approval-holder may obtain any final report resulting from such audit.


(b) No more than once a year except for cause, the approval-holder, at MSHA’s request, shall make an approved product available at no cost to MSHA for an audit to be conducted at a mutually agreeable site and time. The approval-holder may observe any tests conducted during this audit.


(c) An approved product shall be subject to audit for cause at any time MSHA believes that it is not in compliance with the technical requirements upon which the approval was based.


§ 7.9 Revocation.

(a) MSHA may revoke for cause an approval issued under this part if the product:


(1) Fails to meet the applicable technical requirements; or


(2) Creates a hazard when used in a mine.


(b) Prior to revoking an approval, the approval-holder shall be informed in writing of MSHA’s intention to revoke approval. The notice shall:


(1) Explain the specific reasons for the proposed revocation; and


(2) Provide the approval-holder an opportunity to demonstrate or achieve compliance with the product approval requirements.


(c) Upon request, the approval-holder shall be afforded an opportunity for a hearing.


(d) If a product poses an imminent hazard to the safety or health of miners, the approval may be immediately suspended without a written notice of the agency’s intention to revoke. The suspension may continue until the revocation proceedings are completed.


§ 7.10 MSHA acceptance of equivalent non-MSHA product safety standards.

(a) MSHA will accept non-MSHA product safety standards, or groups of standards, as equivalent after determining that they:


(1) Provide at least the same degree of protection as MSHA’s applicable technical requirements for a product in the subparts of this part; or


(2) Can be modified to provide at least the same degree of protection as those MSHA requirements.


(b) MSHA will publish its intent to review any non-MSHA product safety standard for equivalency in the Federal Register for the purpose of soliciting public input.


(c) A listing of all equivalency determinations will be published in this part 7. The listing will state whether MSHA accepts the non-MSHA product safety standards in their original form, or whether MSHA will require modifications to demonstrate equivalency. If modifications are required, they will be provided in the listing. MSHA will notify the public of each equivalency determination and will publish a summary of the basis for its determination. MSHA will provide equivalency determination reports to the public upon request to the Approval and Certification Center. MSHA has made the following equivalency determinations applicable to this part 7.


(1) MSHA will accept applications for motors under Subpart J designed and tested to the International Electrotechnical Commission’s (IEC) standards for Electrical Apparatus for Explosive Gas Atmospheres, Part 0, General Requirements (IEC 60079-0, Fourth Edition, 2004-01) and Part 1, Electrical Apparatus for Explosive Gas Atmospheres, Flameproof Enclosures “d” (IEC 60079-1, Fifth Edition, 2003-11) (which are hereby incorporated by reference and made a part hereof) provided the modifications to the IEC standards specified in § 7.10(c)(1)(i) through (ix) are met. The Director of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. The IEC standards may be inspected at the U.S. Department of Labor, Mine Safety and Health Administration, Electrical Safety Division, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. These IEC standards may be obtained from International Electrical Commission, Central Office 3, rue de Varembé, P.O. Box 131, CH-1211 GENEVA 20, Switzerland.


(i) Enclosures associated with an electric motor assembly shall be made of metal and not have a compartment exceeding ten (10) feet in length. External surfaces of enclosures shall not exceed 150 °C (302 °F) in normal operation.


(ii) Enclosures shall be rugged in construction and should meet existing requirements for minimum bolt size and spacing and for minimum wall, cover, and flange thicknesses specified in paragraph (g)(19) of § 7.304 Technical requirements. Enclosure fasteners should be uniform in size and length, be provided at all corners, and be secured from loosening by lockwashers or equivalent. An engineering analysis shall be provided for enclosure designs that deviate from the existing requirements. The analysis shall show that the proposed enclosure design meets or exceeds the mechanical strength of a comparable enclosure designed to 150 psig according to existing requirements, and that flamepath clearances in excess of existing requirements will not be produced at an internal pressure of 150 psig. This shall be verified by explosion testing the enclosure at a minimum of 150 psig.


(iii) Enclosures shall be designed to withstand a minimum pressure of at least 150 psig without leakage through any welds or castings, rupture of any part that affects explosion-proof integrity, clearances exceeding those permitted under existing requirements along flame-arresting paths, or permanent distortion exceeding 0.040-inch per linear foot.


(iv) Flamepath clearances, including clearances between fasteners and the holes through which they pass, shall not exceed those specified in existing requirements. No intentional gaps in flamepaths are permitted.


(v) The minimum lengths of the flame arresting paths, based on enclosure volume, shall conform to those specified in existing requirements to the nearest metric equivalent value (e.g., 12.5 mm, 19 mm, and 25 mm are considered equivalent to
1/2 inch,
3/4 inch and 1 inch respectively for plane and cylindrical joints). The widths of any grooves for o-rings shall be deducted in measuring the widths of flame-arresting paths.


(vi) Gaskets shall not be used to form any part of a flame-arresting path. If o-rings are installed within a flamepath, the location of the o-rings shall meet existing requirements.


(vii) Cable entries into enclosures shall be of a type that utilizes either flame-resistant rope packing material or sealing rings (grommets). If plugs and mating receptacles are mounted to an enclosure wall, they shall be of explosion-proof construction. Insulated bushings or studs shall not be installed in the outside walls of enclosures. Lead entrances utilizing sealing compounds and flexible or rigid metallic conduit are not permitted.


(viii) Unused lead entrances shall be closed with a metal plug that is secured by spot welding, brazing, or equivalent.


(ix) Special explosion tests are required for electric motor assemblies that share leads (electric conductors) through a common wall with another explosion-proof enclosure, such as a motor winding compartment and a conduit box. These tests are required to determine the presence of any pressure piling conditions in either enclosure when one or more of the insulating barriers, sectionalizing terminals, or other isolating parts are sequentially removed from the common wall between the enclosures. Enclosures that exhibit pressures during these tests that exceed those specified in existing requirements must be provided with a warning tag. The durable warning tag must indicate that the insulating barriers, sectionalizing terminals, or other isolating parts be maintained in order to insure the explosion-proof integrity for either enclosure sharing a common wall. A warning tag is not required if the enclosures withstand a static pressure of twice the maximum value observed in the explosion tests.


(2) [Reserved]


(d) After MSHA has determined that non-MSHA product safety standards are equivalent and has notified the public of such determinations, applicants may seek MSHA product approval based on such non-MSHA product safety standards.


[68 FR 36418, June 17, 2003, as amended at 71 FR 28583, May 17, 2006; 73 FR 52210, Sept. 9, 2008]


Subpart B – Brattice Cloth and Ventilation Tubing

§ 7.21 Purpose and effective date.

This subpart establishes the specific requirements for approval of brattice cloth and ventilation tubing. It is effective August 22, 1988. Applications for approval or extension of approval submitted after August 22, 1989, shall meet the requirements of this part.


§ 7.22 Definitions.

The following definitions apply in this subpart:


Brattice cloth. A curtain of jute, plastic, or similar material used to control or direct ventilating air.


Denier. A unit of yarn size indicating the fineness of fiber of material based on the number of grams in a length of 9,000 meters.


Film. A sheet of flexible material applied to a scrim by pressure, temperature, adhesion, or other method.


Scrim. A substrate material of plastic or fabric laminated between or coated with a film.


Ventilation tubing. Rigid or flexible tubing used to convey ventilating air.


§ 7.23 Application requirements.

(a) Brattice cloth. A single application may address two or more products if the products differ only in: weight of the finished product; weight or weave of the same fabric or scrim; or thickness or layers of the same film. Applications shall include the following information:


(1) Trade name.


(2) Product designations (for example, style and code number).


(3) Color.


(4) Type of brattice (for example, plastic or jute).


(5) Weight of finished product.


(6) Film: type, weight, thickness, supplier, supplier’s stock number or designation, and percent of finished product by weight.


(7) Scrim: Type, denier, weight, weave, the supplier, supplier’s stock number or designation, and percent of finished product by weight.


(8) Adhesive: type, supplier, supplier’s stock number or designation, and percent of finished product by weight.


(b) Flexible ventilation tubing. Applications shall include the product description information in paragraph (a) of this section and list the type of supporting structure, if applicable; inside diameters; and configurations.


(c) Rigid ventilation tubing. A single application may address two or more products if the products differ only in diameters, lengths, configuration, or average wall thickness. Applications shall include the following information:


(1) Trade name.


(2) Product designations (for example, style and code numbers).


(3) Color.


(4) Type of ventilation tubing (for example, fiberglass, plastic, or polyethylene).


(5) Inside diameter, configuration, and average wall thickness.


(6) Suspension system (for example, metal hooks).


(7) Base material: type, supplier, the supplier’s stock number, and percent of finished product by weight.


(8) Resin: type, supplier, the supplier’s stock number, and percent of finished product by weight.


(9) Flame retardant, if added during manufacturing: type, supplier, the supplier’s stock number, and percent of finished product by weight.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33722, June 29, 1995]


§ 7.24 Technical requirements.

(a) Brattice cloth shall be flame resistant when tested in accordance with the flame resistance test in § 7.27.


(b) Flexible ventilation tubing shall be manufactured using an MSHA-approved brattice cloth. If a supporting structure is used, it shall be metal or other noncombustible material which will not ignite, burn, support combustion or release flammable vapors when subjected to fire or heat.


(c) Rigid ventilation tubing shall be flame resistant when tested in accordance with the flame resistance test in § 7.28.


§ 7.25 Critical characteristics.

A sample of each batch or lot of brattice cloth and ventilation tubing shall be flame tested or a sample of each batch or lot of the materials that contribute to the flame-resistance characteristic shall be inspected or tested to ensure that the finished product will meet the flame-resistance test.


§ 7.26 Flame test apparatus.

The principal parts of the apparatus used to test for flame-resistance of brattice cloth and ventilation tubing shall be constructed as follows:


(a) A 16-gauge stainless steel gallery lined on the top, bottom and both sides with
1/2 inch thick Marinite or equivalent insulating material yielding inside dimensions approximately 58 inches long, 41 inches high, and 30 inches wide;


(b) Two
3/8-inch diameter steel J hooks and a
9/16-inch diameter steel rod to support the sample located approximately 2
3/16-inches from the front and back ends of the test gallery, 1
1/2-inches from the ceiling insulation and centrally located in the gallery along its length. Samples shall be suspended to preclude folds or wrinkles;


(c) A tapered 16-gauge stainless steel duct section tapering from a cross sectional area measuring 2 feet 7 inches wide by 3 feet 6 inches high at the test gallery to a cross-sectional area 1 foot 6 inches square over a length of 3 feet. The tapered duct section must be tightly connected to the test gallery;


(d) A 16-gauge stainless steel fan housing, consisting of a 1 foot 6 inches square section 6 inches long followed by a 10 inch long section which tapers from 1 foot 16 inches square to 12 inches diameter round and concluding with a 12 inch diameter round collar 3 inches long. A variable speed fan capable of producing an air velocity of 125 ft./min. in the test gallery must be secured in the fan housing. The fan housing must be tightly connected to the tapered duct section;


(e) A methane-fueled impinged jet burner igniting source, measuring 12 inches long from the threaded ends of the first and last jets and 4 inches wide with 12 impinged jets, approximately 1
3/8-inches long and spaced alternately along the length of the burner tube. The burner jets must be canted so that they point toward each other in pairs and the flame from these pairs impinge upon each other.


§ 7.27 Test for flame resistance of brattice cloth.

(a) Test procedures. (1) Prepare 6 samples of brattice cloth 40 inches wide by 48 inches long.


(2) Prior to testing, condition each sample for a minimum of 24 hours at a temperature of 70 ±10 °F (21 ±5.5 °C) and a relative humidity of 55 ±10%.


(3) For each test, suspend the sample in the gallery by wrapping the brattice cloth around the rod and clamping each end and the center. The brattice cloth must hang 4 inches from the gallery floor.


(4) Use a front exhaust system to remove smoke escaping from the gallery. The exhaust system must remain on during all testing, but not affect the air flow in the gallery.


(5) Set the methane-fueled impinged jet burner to yield a flame height of 12 inches as measured at the outermost tip of the flame.


(6) Apply the burner to the front lower edge of the brattice cloth and keep it in contact with the material for 25 seconds or until 1 foot of material, measured horizontally, is consumed, whichever occurs first. If the material shrinks during application of the burner flame, move the burner flame to maintain contact with 1 foot of the material. If melting material might clog the burner orifices, rotate the burner slightly during application of the flame.


(7) Test 3 samples in still air and 3 samples with an average of 125 ft./min. of air flowing past the sample.


(8) Record the propagation length and duration of burning for each of the 6 samples. The duration of burning is the total burning time of the specimen during the flame test. This includes the burn time of any material that falls on the floor of the test gallery during the igniting period. However, the suspended specimen is considered burning only after the burner is removed. Should the burning time of a suspended specimen and a specimen on the floor coincide, count the coinciding burning time only once.


(9) Calculate the average duration of burning for the first 3 samples (still air) and the second 3 samples (125 ft./min. air flow).


(b) Acceptable performance. The brattice cloth shall meet each of the following criteria:


(1) Flame propagation of less than 4 feet in each of the six tests.


(2) An average duration of burning of less than 1 minute in both groups of three tests.


(3) A duration of burning not exceeding two minutes in each of the six tests.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 7.28 Test for flame resistance of rigid ventilation tubing.

(a) Test procedures. (1) Prepare 6 samples of ventilation tubing 48 inches in length with all flared or thickened ends removed. Any sample with a cross-sectional dimension greater than 24 inches must be tested in a 24-inch size.


(2) For each test, suspend the sample in the center of the gallery by running a wire through the 48-inch length of tubing.


(3) Use a front exhaust system to remove smoke escaping from the gallery. The exhaust system must remain on during all testing but not affect the air flow in the gallery.


(4) Set the methane-fueled impinged jet burner to yield a flame height of 12 inches as measured at the outermost tip of the flame.


(5) Apply the burner to the front lower edge of the tubing so that two-thirds of the burner is under the tubing and the remaining third is exposed to allow the flames to curl onto the inside of the tubing. Keep the burner in contact with the material for 60 seconds. If melting material might clog the burner orifices, rotate the burner slightly during application of the flame.


(6) Test 3 samples in still air and 3 samples with an average of 125 ft./min. of air flowing past the sample.


(7) Record the propagation length and duration of burning for each of the 6 samples. The duration of burn is the total burning time of the specimen during the flame test. This includes the burning time of any material that falls on the floor of the test gallery during the igniting period. However, the suspended specimen is considered burning only after the burner is removed. Should the burning time of a suspended specimen and a specimen on the floor coincide, count the coinciding burn time only once.


(8) Calculate the average duration of burning for the first 3 samples (still air) and the second 3 samples (125 ft./min. air flow).


(b) Acceptable performance. The ventilation tubing shall meet each of the following criteria:


(1) Flame propagation of less than 4 feet in each of the 6 tests.


(2) An average duration of burning of less than 1 minute in both groups of 3 tests.


(3) A duration of burning not exceeding 2 minutes in each of the 6 tests.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 7.29 Approval marking.

(a) Approved brattice cloth shall be legibly and permanently marked with the assigned MSHA approval number at intervals not exceeding ten feet. If the nature of the material or method of processing makes such marking impractical, permanent paint or ink may be used to mark the edge with an MSHA-assigned color code.


(b) Approved ventilation tubing shall be legibly and permanently marked on each section with the assigned MSHA approval number.


(c) An approved product shall be marketed only under a brand or trade name that has been furnished to MSHA.


§ 7.30 Post-approval product audit.

Upon request by MSHA but no more than once a year except for cause, the approval-holder shall supply to MSHA at no cost up to fifty feet of each approved design of brattice cloth and ventilation tubing for audit.


§ 7.31 New technology.

MSHA may approve brattice cloth and ventilation tubing that incorporates technology for which the requirements of this subpart are not applicable, if the Agency determines that the product is as safe as those which meet the requirements of this subpart.


Subpart C – Battery Assemblies

§ 7.41 Purpose and effective date.

This subpart establishes the specific requirements for MSHA approval of battery assemblies intended for incorporation in approved equipment in underground mines. It is effective August 22, 1988. Applications for approval or extensions of approval submitted after August 22, 1989, shall meet the requirements of this part.


§ 7.42 Definitions.

The following definitions apply in this subpart:


Battery assembly. A unit or units consisting of cells and their electrical connections, assembled in a battery box or boxes with covers.


Battery box. The exterior sides, bottom, and connector receptacle compartment, if any, of a battery assembly, excluding internal partitions.


§ 7.43 Application requirements.

(a) An application for approval of a battery assembly shall contain sufficient information to document compliance with the technical requirements of this subpart and include a composite drawing with the following information:


(1) Overall dimensions of the battery assembly, including the minimum distance from the underside of the cover to the top of the terminals and caps.


(2) Composition and thicknesses of the battery box and cover.


(3) Provision for securing covers.


(4) Documentation of flame-resistance of insulating materials and cables.


(5) Number, type, and rating of the battery cells.


(6) Diagram of battery connections between cells and between battery boxes, except when connections between battery boxes are a part of the machine’s electrical system.


(7) Total weight of the battery, charged and ready for service.


(8) Documentation of materials and configurations for battery cells, intercell connectors, filler caps, and battery top:


(i) If nonmetallic cover designs are used with cover support blocks; or


(ii) If the cover comes into contact with any portion of the cells, caps, filler material, battery top, or intercell connectors during the impact test specified by § 7.46.


(b) All drawings shall be titled, dated, numbered, and include the latest revision number.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 7.44 Technical requirements.

(a)(1) Battery boxes and covers constructed of AISI 1010 hot rolled steel shall have the following minimum thicknesses based on the total weight of a unit of the battery assembly charged and ready for service:


Weight of battery unit
Minimum required thickness
1,000 lbs. maximum10 gauge or
1/8″ nominal
1,001 to 2,000 lbs7 gauge or
3/16″ nominal
2,001 to 4,500 lbs3 gauge or
1/4″ nominal
Over 4,500 lbs0 gauge or
5/16″ nominal

(2) Battery boxes not constructed of AISI 1010 hot rolled steel shall have at least the tensile strength and impact resistance of battery boxes for the same weight class, as listed in paragraph (a)(1) of this section.


(3) Battery box covers constructed of materials with less than the tensile strength and impact resistance of AISI 1010 hot rolled steel or constructed of nonmetallic materials shall meet the acceptable performance criteria for the impact test in § 7.46. Nonmetallic covers shall be used only in the battery assembly configuration in which they pass the impact test.


(4) Nonmetallic materials for boxes and covers shall –


(i) Be accepted by MSHA as flame-resistant material under part 18 of this chapter; and


(ii) Meet the acceptable performance criteria for the deflection temperature test in § 7.47.


(b) All insulating material shall have a minimum resistance of 100 megohms at 500 volts d.c. and be accepted by MSHA as flame resistant under part 18 of this chapter.


(c) Battery box and cover insulating material shall meet the acceptable performance criteria for the acid resistance test in § 7.48.


(d) Covers shall be lined with insulating material permanently attached to the underside of the cover, unless the cover is constructed of insulating material.


(e) Covers, including those used over connector receptacle housings, shall be provided with a means of securing them in a closed position.


(f) Battery boxes shall be provided with vent openings to prevent the accumulation of flammable or toxic gases or vapors within the battery assembly. The size and location of openings shall prevent direct access to cell terminals and other uninsulated current carrying parts. The total minimum unobstructed cross-sectional area of the ventilation openings shall be no less than the value determined by the following formula:




N = Number of cells in battery box.

R = Rated 6 hour battery capacity in ampere hours.

M = Total minimum ventilation area in square inches per battery box.

(g) Battery boxes shall have drainage holes to prevent accumulation of water or electrolyte.


(h) Battery cells shall be insulated from the battery box walls, partitions and bottom by insulating material, unless such part of the battery box is constructed of insulating material. Battery box wall insulating material shall extend to the top of the wall.


(i) Cell terminals shall be burned on, except that bolted connectors using two or more bolts may be used on end terminals.


(j) Battery connections shall be designed so that total battery potential is not available between adjacent cells.


(k) Cables within a battery box shall be accepted by MSHA as flame resistant under part 18 of this chapter or approved under subpart K of this part. The cables shall be protected against abrasion by insulation, location, clamping, or other effective means.


(l) When the battery plug and receptacle are not located on or within the battery box, strain on the battery terminals shall be prevented by a strain-relief device on the cable. Insulating material shall be placed between the strain-relief device and cable, unless the device is constructed of insulating material.


(m) At least a
1/2-inch air space shall be provided between the underside of the battery cover and the top of the battery, including the terminals and connectors.


[53 FR 23500, June 22, 1988, as amended at 57 FR 61220, Dec. 23, 1992]


§ 7.45 Critical characteristics

The following critical characteristics shall be inspected or tested on each battery assembly to which an approval marking is affixed:


(a) Thickness of covers and boxes.


(b) Application and resistance of insulating material.


(c) Size and location of ventilation openings.


(d) Method of cell terminations.


(e) Strain relief devices for cables leaving boxes.


(f) Type, location, and physical protection of cables.


§ 7.46 Impact test.

(a) Test procedures. (1) Prepare four covers for testing by conditioning two covers at −13 °F (−25 °C) and two covers at 122 °F (50 °C) for a period of 48 hours.


(2) Mount the covers on a battery box of the same design with which the covers are to be approved, including any support blocks, with the battery cells completely assembled. If used, support blocks must contact only the filler material or partitions between the individual cells. At the test temperature range of 65 °F-80 °F (18.3 °C-26.7 °C), apply a dynamic force of 200 ft. lbs. to the following areas using a hemispherical weight with a 6″ maximum radius:


(i) The center of the two largest unsupported areas;


(ii) The areas above at least two support blocks, if used;


(iii) The areas above at least two intercell connectors, one cell, and one filler cap; and


(iv) Areas on at least two corners. If the design consists of both inside and outside corners, test one of each.


(3) Record the condition of the covers, supports, intercell connectors, filler caps, cell covers, and filler material.


(b) Acceptable performance. Impact tests of any of the four covers shall not result in any of the following:


(1) Bent intercell connectors.


(2) Cracked or broken filler caps, except plastic tabs which extend from the body of the filler caps.


(3) Cracks in the cell cover, cells, or filler material.


(4) Cracked or bent supports.


(5) Cracked or splintered battery covers.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 7.47 Deflection temperature test.

(a) Test procedures. (1) Prepare two samples for testing that measure 5 inches by
1/2 inch, by the thickness of the material as it will be used. Prior to testing, condition the samples at 73.4 ±3.6 °F (23 ±2 °C) and 50 ±5% relative humidity for at least 40 hours.


(2) Place a sample on supports which are 4 inches apart and immersed in a heat transfer medium at a test temperature range of 65 °F−80 °F (18.3 °C−26.7 °C). The heat transfer medium must be a liquid which will not chemically affect the sample. The testing apparatus must be constructed so that expansion of any components during heating of the medium does not result in deflection of the sample.


(3) Place a temperature measuring device with an accuracy of 1% into the heat transfer medium within
1/8 inch of, but not touching, the sample.


(4) Apply a total load, in pounds, numerically equivalent to 11 times the thickness of the sample, in inches, to the sample midway between the supports using a
1/8 inch radius, rounded contact. The total load includes that weight used to apply the load and any force exerted by the deflection measurement device.


(5) Use a deflection measuring device with an accuracy of ±.001 inches to measure the deflection of the sample at the point of loading as the temperature of the medium is increased at a uniform rate of 3.6 ±.36 °F/min. (2 ±0.2 °C/min.). Apply the load to the sample for 5 minutes prior to heating, to allow compensation for creep in the sample due to the loading.


(6) Record the deflection of the sample due to heating at 180 °F (82 °C).


(7) Repeat steps 2 through 6 for the other sample.


(b) Acceptable performance. Neither sample shall have a deflection greater than .010 inch at 180 °F (82 °C).


[53 FR 23500, June 22, 1988; 53 FR 25569, July 7, 1988; 60 FR 33723, June 29, 1995]


§ 7.48 Acid resistance test.

(a) Test procedures. (1) Prepare one sample each of the insulated surfaces of the battery box and of the cover that measure at least 4 inches by 8 inches, by the thickness of the sample which includes the insulation plus the battery cover or box material. The insulation thickness shall be representative of that used on the battery box and cover. If the insulation material and thickness of material are identical for the battery box and cover, only one sample need be prepared and tested.


(2) Prepare a 30 percent solution of sulfuric acid (H2 SO4) by mixing 853 ml of water with 199 ml of sulfuric acid (H2 SO4) with a specific gravity of 1.84. Completely cover the samples with the acid solution at the test temperature range of 65 °F−80 °F (18.3 °C−26.7 °C) and maintain these conditions for 7 days.


(3) After 7 days, record the condition of the samples.


(b) Acceptable performance. At the end of the test, the insulation shall not exhibit any blistering, discoloration, cracking, swelling, tackiness, rubberiness, or loss of bond.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 7.49 Approval marking.

Each approved battery assembly shall be identified by a legible and permanent approval plate inscribed with the assigned MSHA approval number and securely attached to the battery box.


§ 7.50 Post-approval product audit.

Upon request by MSHA, but no more than once a year except for cause, the approval-holder shall make an approved battery assembly available for audit at no cost to MSHA.


§ 7.51 Approval checklist.

Each battery assembly bearing an MSHA approval plate shall be accompanied by a description of what is necessary to maintain the battery assembly as approved.


[53 FR 23500, June 22, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 7.52 New technology.

MSHA may approve a battery assembly that incorporates technology for which the requirements of this subpart are not applicable, if the Agency determines that the battery assembly is as safe as those which meet the requirements of this subpart.


Subpart D – Multiple-Shot Blasting Units


Source:54 FR 48210, Nov. 21, 1989, unless otherwise noted.

§ 7.61 Purpose and effective date.

This subpart establishes the specific requirements for MSHA approval of multiple-shot blasting units. It is effective January 22, 1990. Applications for approval or extensions of approval submitted after January 22, 1991 shall meet the requirements of this subpart.


§ 7.62 Definitions.

The following definitions apply in this subpart:


Blasting circuit. A circuit that includes one or more electric detonators connected in a single series and the firing cable used to connect the detonators to the blasting unit.


Blasting unit. An electric device used to initiate electric detonators.


Normal operation. Operation of the unit according to the manufacturer’s instructions with fully-charged batteries, with electric components at any value within their specified tolerances, and with adjustable electric components set to any value within their range.


§ 7.63 Application requirements.

(a) Each application for approval of a blasting unit shall include the following:


(1) An overall assembly drawing showing the physical construction of the blasting unit.


(2) A schematic diagram of the electric circuit.


(3) A parts list specifying each electric component and its electrical ratings, including tolerances.


(4) A layout drawing showing the location of each component and wiring.


(5) The model number or other manufacturer’s designation of the blasting unit.


(b) All drawings shall be titled, numbered, dated, and include the latest revision number. The drawings may be combined into one or more composite drawings.


(c) The application shall contain a list of all the drawings submitted, including drawing titles, numbers, and revisions.


(d) A detailed technical description of the operation and use of the blasting unit shall be submitted with the application.


[54 FR 48210, Nov. 21, 1989, as amended at 60 FR 33723, June 29, 1995]


§ 7.64 Technical requirements.

(a) Energy output. Blasting units shall meet the acceptable performance criteria of the output energy test in § 7.66.


(b) Maximum blasting circuit resistance. The maximum value of the resistance of the blasting circuit that can be connected to the firing line terminals of the blasting unit, without exceeding its capacity, shall be specified by the applicant. The specified maximum blasting circuit resistance shall be at least 150 ohms.


(c) Visual indicator. The blasting unit shall provide a visual indication to the user prior to the operation of the firing switch when the voltage necessary to produce the required firing current is attained.


(d) Firing switch. The switch used to initiate the application of energy to the blasting circuit shall –


(1) Require deliberate action for its operation to prevent accidental firing; and


(2) Operate only when the voltage necessary to produce the required firing current is available to the blasting circuit.


(e) Firing line terminals. The terminals used to connect the blasting circuit to the blasting unit shall –


(1) Provide a secure, low-resistance connection to the blasting circuit as demonstrated by the firing line terminals test in § 7.68;


(2) Be corrosion-resistant;


(3) Be insulated to protect the user from electrical shock; and


(4) Be separated from each other by an insulated barrier.


(f) Ratings of electric components. No electric component of the blasting unit, other than batteries, shall be operated at more than 90 percent of any of its electrical ratings in the normal operation of the blasting unit.


(g) Non-incendive electric contacts. In the normal operation of a blasting unit, the electric energy discharged by making and breaking electric contacts shall not be capable of igniting a methane-air atmosphere, as determined by the following:


(1) The electric current through an electric contact shall not be greater than that determined from Figure D-1.


(2) The maximum voltage that can be applied across an electric contact that discharges a capacitor shall not be greater than that determined from Figure D-2.


(3) The electric current through an electric contact that interrupts a circuit containing inductive components shall not be greater than that determined from Figure D-3. Inductive components include inductors, chokes, relay coils, motors, transformers, and similar electric components that have an inductance greater than 100 microhenries. No inductive component in a circuit with making and breaking electric contacts shall have an inductance value greater than 100 millihenries.





(h) Maximum temperature. In the normal operation of the blasting unit, the maximum temperature of any electric component shall not exceed 302 °F (150 °C).


(i) Capacitor discharge. The blasting unit shall include an automatic means to dissipate any electric charge remaining in any capacitor after the blasting unit is deenergized and not in use.


(j) Construction. Blasting units shall meet the acceptable performance criteria of the construction test of § 7.67.


(k) Locking device. The blasting unit shall be equipped with a locking device to prevent unauthorized use.


(l) Enclosure. The blasting unit enclosure shall be protected against tampering by –


(1) Sealing the enclosure, except the battery compartment, using continuous welding, brazing, soldering, or equivalent methods; or


(2) Sealing the electric components, other than batteries, in a solidified insulating material and assembling the enclosure with tamper-resistant hardware.


(m) Battery charging. Blasting units that contain rechargeable batteries shall have the following:


(1) A blocking diode, or equivalent device, in series with the battery to prevent electric energy in the battery from being available at the charging connector.


(2) The charging connector recessed into the enclosure.


§ 7.65 Critical characteristics.

The following critical characteristics shall be inspected or tested on each blasting unit to which an approval marking is affixed:


(a) The output current.


(b) The voltage cut-off time.


(c) The components that control voltage and current through each making and breaking electric contact.


(d) Operation of the visual indicator and the firing switch.


§ 7.66 Output energy test.

(a) Test procedures. The blasting unit shall be tested by firing into each of the following resistive loads, within a tolerance of ±1%:


(1) The maximum blasting circuit resistance.


(2) Any resistive load between 3 ohms and the maximum blasting circuit resistance.


(3) One ohm.


(b) Acceptable performance. (1) The voltage shall be zero at the firing line terminals 10 milliseconds after operation of the firing switch.


(2) The electric current from the blasting unit shall be:


(i) Less than 50 milliamperes except during firing of the blasting unit.


(ii) Available only through the firing line terminals.


(iii) At least an average of 2 amperes during the first 5 milliseconds following operation of the firing switch.


(iv) Not exceed an average of 100 amperes during the first 10 milliseconds following operation of the firing switch.


§ 7.67 Construction test.

The construction test is to be performed on the blasting unit subsequent to the output energy test of § 7.66.


(a) Test procedures. (1) The blasting unit shall be dropped 20 times from a height of 3 feet onto a horizontal concrete floor. When dropped, the orientation of the blasting unit shall be varied each time in an attempt to have a different surface, corner, or edge strike the floor first for each drop.


(2) After the blasting unit has been drop tested in accordance with paragraph (a)(1) above, it shall be submerged in 1 foot of water for 1 hour in each of 3 tests. The water temperature shall be maintained within ±5 °F (±2.8 °C) of 40 °F (4.4 °C), 70 °F (21.1 °C) and 100 °F (37.8 °C) during the tests.


(3) Immediately after removing the blasting unit from the water at each temperature, the unit shall be operated first with the firing line terminals open circuited, then operated again with the firing line terminals short circuited, and last, the output energy tested in accordance with the output energy test of § 7.66.


(b) Acceptable performance. (1) The blasting unit shall meet the acceptable performance criteria of the output energy test in § 7.66 each time it is performed.


(2) There shall be no damage to the firing line terminals that exposes an electric conductor.


(3) The visual indicator shall be operational.


(4) The batteries shall not be separated from the blasting unit.


(5) There shall be no water inside the blasting unit enclosure, except for the battery compartment.


§ 7.68 Firing line terminals test.

(a) Test procedures. (1) The contact resistance through each firing line terminal shall be determined.


(2) A 10-pound pull shall be applied to a No. 18 gauge wire that has been connected to each firing line terminal according to the manufacturer’s instructions.


(b) Acceptable performance. (1) The contact resistance shall not be greater than 1 ohm.


(2) The No. 18 gauge wire shall not become disconnected from either firing line terminal.


§ 7.69 Approval marking.

Each approved blasting unit shall be identified as permissible by a legible and permanent marking securely attached, stamped, or molded to the outside of the unit. This marking shall include the following:


(a) The assigned MSHA approval number.


(b) The maximum blasting circuit resistance.


(c) A warning that the unit’s components must not be disassembled or removed.


(d) The replacement battery types if the unit has replaceable batteries.


(e) A warning placed next to the charging connector that the battery only be charged in a fresh air location if rechargeable batteries are used.


(f) A warning that the unit is compatible only with detonators that will –


(1) Fire when an average of 1.5 amperes is applied for 5 milliseconds;


(2) Not misfire when up to an average 100 amperes is applied for 10 milliseconds; and


(3) Not fire when a current of 250 milliamperes or less is applied.


§ 7.70 Post-approval product audit.

Upon request by MSHA, but not more than once a year except for cause, the approval holder shall make an approved blasting unit available for audit at no cost to MSHA.


§ 7.71 Approval checklist.

Each blasting unit bearing an MSHA approval marking shall be accompanied by a description of what is necessary to maintain the blasting unit as approved.


[54 FR 48210, Nov. 21, 1989, as amended at 60 FR 33723, June 29, 1995]


§ 7.72 New technology.

MSHA may approve a blasting unit that incorporates technology for which the requirements of this subpart are not applicable if the Agency determines that the blasting unit is as safe as those which meet the requirements of this subpart.


Subpart E – Diesel Engines Intended for Use in Underground Coal Mines


Source:61 FR 55504, Oct. 25, 1996, unless otherwise noted.

§ 7.81 Purpose and effective date.

Subpart A general provisions of this part apply to this subpart E. Subpart E establishes the specific engine performance and exhaust emission requirements for MSHA approval of diesel engines for use in areas of underground coal mines where permissible electric equipment is required and areas where non-permissible electric equipment is allowed. It is effective November 25, 1996.


§ 7.82 Definitions.

In addition to subpart A definitions of this part, the following definitions apply in this subpart.


Brake Power. The observed power measured at the crankshaft or its equivalent when the engine is equipped only with standard auxiliaries necessary for its operation on the test bed.


Category A engines. Diesel engines intended for use in areas of underground coal mines where permissible electric equipment is required.


Category B engines. Diesel engines intended for use in areas of underground coal mines where nonpermissible electric equipment is allowed.


Corrosion-resistant material. Material that has at least the corrosion-resistant properties of type 304 stainless steel.


Diesel engine. Any compression ignition internal combustion engine using the basic diesel cycle where combustion results from the spraying of fuel into air heated by compression.


Exhaust emission. Any substance emitted to the atmosphere from the exhaust port of the combustion chamber of a diesel engine.


Intermediate speed. Maximum torque speed if it occurs between 60 percent and 75 percent of rated speed. If the maximum torque speed is less than 60 percent of rated speed, then the intermediate speed shall be 60 percent of the rated speed. If the maximum torque speed is greater than 75 percent of the rated speed, then the intermediate speed shall be 75 percent of rated speed.


Low idle speed. The minimum no load speed as specified by the engine manufacturer.


Maximum torque speed. The speed at which an engine develops maximum torque.


Operational range. All speed and load (including percent loads) combinations from the rated speed to the minimum permitted engine speed at full load as specified by the engine manufacturer.


Particulates. Any material collected on a specified filter medium after diluting exhaust gases with clean, filtered air at a temperature of less than or equal to 125 °F (52 °C), as measured at a point immediately upstream of the primary filter. This is primarily carbon, condensed hydrocarbons, sulfates, and associated water.


Percent load. The fraction of the maximum available torque at an engine speed.


Rated horsepower. The nominal brake power output of a diesel engine as specified by the engine manufacturer with a specified production tolerance. For laboratory test purposes, the fuel pump calibration for the rated horsepower must be set between the nominal and the maximum fuel tolerance specification.


Rated speed. Speed at which the rated power is delivered, as specified by the engine manufacturer.


Steady-state condition. Diesel engine operating condition which is at a constant speed and load and at stabilized temperatures and pressures.


Total oxides of nitrogen. The sum total of the measured parts per millions (ppm) of nitric oxide (NO) plus the measured ppm of nitrogen dioxide (NO2).


§ 7.83 Application requirements.

(a) An application for approval of a diesel engine shall contain sufficient information to document compliance with the technical requirements of this subpart and specify whether the application is for a category A engine or category B engine.


(b) The application shall include the following engine specifications –


(1) Model number;


(2) Number of cylinders, cylinder bore diameter, piston stroke, engine displacement;


(3) Maximum recommended air inlet restriction and exhaust backpressure;


(4) Rated speed(s), rated horsepower(s) at rated speed(s), maximum torque speed, maximum rated torque, high idle, minimum permitted engine speed at full load, low idle;


(5) Fuel consumption at rated horsepower(s) and at the maximum rated torque;


(6) Fuel injection timing; and


(7) Performance specifications of turbocharger, if applicable.


(c) The application shall include dimensional drawings (including tolerances) of the following components specifying all details affecting the technical requirements of this subpart. Composite drawings specifying the required construction details may be submitted instead of individual drawings of the following components –


(1) Cylinder head;


(2) Piston;


(3) Inlet valve;


(4) Exhaust valve;


(5) Cam shaft – profile;


(6) Fuel cam shaft, if applicable;


(7) Injector body;


(8) Injector nozzle;


(9) Injection fuel pump;


(10) Governor;


(11) Turbocharger, if applicable;


(12) Aftercooler, if applicable;


(13) Valve guide;


(14) Cylinder head gasket; and


(15) Precombustion chamber, if applicable.


(d) The application shall include a drawing showing the general arrangement of the engine.


(e) All drawings shall be titled, dated, numbered, and include the latest revision number.


(f) When all necessary testing has been completed, the following information shall be submitted:


(1) The gaseous ventilation rate for the rated speed and horsepower.


(2) The particulate index for the rated speed and horsepower.


(3) A fuel deration chart for altitudes for each rated speed and horsepower.


§ 7.84 Technical requirements.

(a) Fuel injection adjustment. The fuel injection system of the engine shall be constructed so that the quantity of fuel injected can be controlled at a desired maximum value. This adjustment shall be changeable only after breaking a seal or by altering the design.


(b) Maximum fuel-air ratio. At the maximum fuel-air ratio determined by § 7.87 of this part, the concentrations (by volume, dry basis) of carbon monoxide (CO) and oxides of nitrogen (NOX) in the undiluted exhaust gas shall not exceed the following:


(1) There shall be no more than 0.30 percent CO and no more than 0.20 percent NOX for category A engines.


(2) There shall be no more than 0.25 percent CO and no more than 0.20 percent NOX for category B engines.


(c) Gaseous emissions ventilation rate. Ventilation rates necessary to dilute gaseous exhaust emissions to the following values shall be determined under § 7.88 of this part:


Carbon dioxide−5000 ppm
Carbon monoxide−50 ppm
Nitric oxide−25 ppm
Nitrogen dioxide−5 ppm

A gaseous ventilation rate shall be determined for each requested speed and horsepower rating as described in § 7.88(b) of this part.

(d) Fuel deration. The fuel rates specified in the fuel deration chart shall be based on the tests conducted under paragraphs (b) and (c) of this section and shall ensure that the maximum fuel:air (f/a) ratio determined under paragraph (b) of this section is not exceeded at the altitudes specified in the fuel deration chart.


(e) Particulate index. For each rated speed and horsepower requested, the particulate index necessary to dilute the exhaust particulate emissions to 1 mg/m
3 shall be determined under § 7.89 of this part.


§ 7.85 Critical characteristics.

The following critical characteristics shall be inspected or tested on each diesel engine to which an approval marking is affixed –


(a) Fuel rate is set properly; and


(b) Fuel injection pump adjustment is sealed, if applicable.


§ 7.86 Test equipment and specifications.

(a) Dynamometer test cell shall be used in determining the maximum f/a ratio, gaseous ventilation rates, and the particulate index.


(1) The following testing devices shall be provided:


(i) An apparatus for measuring torque that provides an accuracy of ±2.0 percent based on the engine’s maximum value;


(ii) An apparatus for measuring revolutions per minute (rpm) that provides an accuracy of ±2.0 percent based on the engine’s maximum value;


(iii) An apparatus for measuring temperature that provides an accuracy of ±4 °F (2 °C) of the absolute value except for the exhaust gas temperature device that provides an accuracy of ±27 °F (15 °C);


(iv) An apparatus for measuring intake and exhaust restriction pressures that provides an accuracy of ±5 percent of maximum;


(v) An apparatus for measuring atmospheric pressure that provides an accuracy of ±0.5 percent of reading;


(vi) An apparatus for measuring fuel flow that provides an accuracy of ±2 percent based on the engine’s maximum value;


(vii) An apparatus for measuring the inlet air flow rate of the diesel engine that provides an accuracy of ±2 percent based on the engine’s maximum value; and


(viii) For testing category A engines, an apparatus for metering in 1.0 ±0.1 percent, by volume, of methane (CH4) into the intake air system shall be provided.


(2) The test fuel specified in Table E-1 shall be a low volatile hydrocarbon fuel commercially designated as “Type 2-D” grade diesel fuel. The fuel may contain nonmetallic additives as follows: Cetane improver, metal deactivator, antioxidant, dehazer, antirust, pour depressant, dye, dispersant, and biocide.


Table E-1 – Diesel Test Fuel Specifications

Item
ASTM
Type 2-D
Cetane numberD61340-48
Cetane indexD97640-48
Distillation range:
IBP °FD86340-400
(°C)(171.1-204.4)
10 pct. point, °FD86400-460
(°C)(204.4-237.8)
50 pct. point, °FD86470.540
(°C)(243.3-282.2)
90 pct. point, °FD86560-630
(°C)(293.3-332.2)
EP, °FD86610-690
(°C)(321.1-365.6)
Gravity,°APID28732-37
Total sulfur, pct.D26220.03-0.05
Hydrocarbon composition:
Aromatics, pct.D131927 minimum
Paraffins, naphthenes, olefinsD1319Remainder
Flashpoint, minimum, °F93130
(°C)(54.4)
Viscosity, centistokes4452.0-3.2

(3) The test fuel temperature at the inlet to the diesel engine’s fuel injection pump shall be controlled to the engine manufacturer’s specification.


(4) The engine coolant temperature (if applicable) shall be maintained at normal operating temperatures as specified by the engine manufacturer.


(5) The charge air temperature and cooler pressure drop (if applicable) shall be set to within ±7 °F(4 °C) and ±0.59 inches Hg (2kPa) respectively, of the manufacturer’s specification.


(b) Gaseous emission sampling system shall be used in determining the gaseous ventilation rates.


(1) The schematic of the gaseous sampling system shown in Figure E-1 shall be used for testing category A engines. Various configurations of Figure E-1 may produce equivalent results. The components in Figure E-1 are designated as follows –


(i) Filters – F1, F2, F3, and F4;


(ii) Flowmeters – FL1, FL2, FL3, FL4, FL5, FL6, and FL7;


(iii) Upstream Gauges – G1, G2, and G5;


(iv) Downstream Gauges – G3, G4, and G6;


(v) Pressure Gauges – P1, P2, P3, P4, P5, and P6;


(vi) Regulators – R1, R2, R3, R4, R5, R6, and R7;


(vii) Selector Valves – V1, V2, V3, V4, V6, V7, V8, V15, and V19;


(viii) Heated Selector Valves – V5, V13, V16, and V17;


(ix) Flow Control Valves – V9, V10, V11 and V12;


(x) Heated Flow Control Valves – V14 and V18;


(xi) Pump – Sample Transfer Pump;


(xii) Temperature Sensor – (T1);


(xiii) Dryer – D1 and D2; and


(xiv) Water traps – WT1 and WT2.


(A) Water removal from the sample shall be done by condensation.


(B) The sample gas temperature or dew point shall be monitored either within the water trap or downstream of the water trap and shall not exceed 45 °F (7 °C).


(C) Chemical dryers are not permitted.



(2) The schematic of the gaseous sampling system shown in Figure E-2 shall be used for testing category B engines. Various configurations of Figure E-2 may produce equivalent results. The components are designated as follows –


(i) Filters – F1, F2, F3, and F4;


(ii) Flowmeters – FL1, FL2, FL3, and FL4;


(iii) Upstream Gauges – G1, and G2;


(iv) Downstream Gauges – G3, and G4;


(v) Pressure Gauges – P1, P2, P3, and P4;


(vi) Regulators – R1, R2, R3, and R4;


(vii) Selector Valves – V1, V2, V3, V4, V6, and V7;


(viii) Heated Selector Valves – V5, V8, and V12;


(ix) Flow Control Valves – V9, V10, V11;


(x) Heated Flow Control Valves – V13;


(xi) Pump – Sample Transfer Pump;


(xii) Temperature Sensor – (T1); and


(xiii) Water traps – WT1 and WT2.


(A) Water removal from the sample shall be done by condensation.


(B) The sample gas temperature or dew point shall be monitored either within the water trap or downstream of the water trap and shall not exceed 45 °F (7 °C).


(C) Chemical dryers are not permitted.


(3) All components or parts of components that are in contact with the sample gas or corrosive calibration gases shall be corrosion-resistant material.



(4) All analyzers shall obtain the sample to be analyzed from the same sample probe.


(5) CO and CO2 measurements shall be made on a dry basis.


(6) Calibration or span gases for the NOX measurement system shall pass through the NO2 to NO converter.


(7) A stainless steel sample probe shall be straight, closed-end, multi-holed, and shall be placed inside the exhaust pipe.


(i) The probe length shall be at least 80 percent of the diameter of the exhaust pipe.


(ii) The inside diameter of the sample probe shall not be greater than the inside diameter of the sample line.


(iii) The heated sample line shall have a 0.197 inch (5 mm) minimum and a 0.53 inch (13.5 mm) maximum inside diameter.


(iv) The wall thickness of the probe shall not be greater than 0.040 inch (1 mm).


(v) There shall be a minimum of 3 holes in 3 different radial planes sized to sample approximately the same flow.


(8) The sample probe shall be located in the exhaust pipe at a minimum distance of 1.6 feet (0.5 meters) or 3 times the diameter of the exhaust pipe, whichever is the larger, from the exhaust manifold outlet flange or the outlet of the turbocharger. The exhaust gas temperature at the sample probe shall be a minimum of 158 °F (70 °C).


(9) The maximum allowable leakage rate on the vacuum side of the analyzer pump shall be 0.5 percent of the in-use flow rate for the portion of the system being checked.


(10) General analyzer specifications. (i) The total measurement error, including the cross sensitivity to other gases, (paragraphs (b)(11)(ii), (b)(12)(iii), (b)(13)(iii), and (b)(13)(iv) of this section), shall not exceed ±5 percent of the reading or ±3.5 percent of full scale, whichever is smaller. For concentrations of less than 100 ppm the measurement error shall not exceed ±4 ppm.


(ii) The repeatability, defined as 2.5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than ±1 percent of full scale concentration for each range used above 155 parts per million (ppm) or parts per million equivalent carbon (ppmC) or ±2 percent of each range used below 155 ppm (or ppmC).


(iii) The analyzer peak to peak response to zero and calibration or span gases over any 10 second period shall not exceed 2 percent of full scale on all ranges used.


(iv) The analyzer zero drift during a 1-hour period shall be less than 2 percent of full scale on the lowest range used. The zero-response is the mean response, including noise, to a zero gas during a 30-second time interval.


(v) The analyzer span drift during a 1-hour period shall be less than 2 percent of full scale on the lowest range used. The analyzer span is defined as the difference between the span response and the zero response. The span response is the mean response, including noise, to a span gas during a 30-second time interval.


(11) CO and CO2 analyzer specifications. (i) Measurements shall be made with nondispersive infrared (NDIR) analyzers.


(ii) For the CO analyzer, the water and CO2 interference shall be less than 1 percent of full scale for ranges equal to or greater than 300 ppm (3 ppm for ranges below 300 ppm) when a CO2 span gas concentration of 80 percent to 100 percent of full scale of the maximum operating range used during testing is bubbled through water at room temperature.


(12) For NOX analysis using a chemiluminescence (CL) analyzer the following parameters shall apply:


(i) From the sample point to the NO2 to NO converter, the NOX sample shall be maintained between 131 °F (55 °C) and 392 °F (200 °C).


(ii) The NO2 to NO converter efficiency shall be at least 90 percent.


(iii) The quench interference from CO2 and water vapor must be less than 3.0 percent.


(13) For NOX analysis using an NDIR analyzer system the following parameters shall apply:


(i) The system shall include a NO2 to NO converter, a water trap, and a NDIR analyzer.


(ii) From the sample point to the NO2 to NO converter, the NOX sample shall be maintained between 131 °F (55 °C) and 392 °F (200 °C).


(iii) The minimum water rejection ratio (maximum water interference) for the NOX NDIR analyzer shall be 5,000:1.


(iv) The minimum CO2 rejection ratio (maximum CO2 interference) for the NOX NDIR analyzer shall be 30,000:1.


(14) When CH4 is measured using a heated flame ionization detector (HFID) the following shall apply:


(i) The analyzer shall be equipped with a constant temperature oven that houses the detector and sample-handling components.


(ii) The detector, oven, and sample-handling components shall be suitable for continuous operation at temperatures of 374 °F (190 °C) ±18 °F (10 °C).


(iii) The analyzer fuel shall contain 40 ±2 percent hydrogen. The balance shall be helium. The mixture shall contain ≤1 part per million equivalent carbon (ppmC), and ≤400 ppm CO.


(iv) The burner air shall contain

(v) The percent of oxygen interference shall be less than 5 percent.


(15) An NDIR analyzer for measuring CH4 may be used in place of the HFID specified in paragraph (b)(14) of this section and shall conform to the requirements of paragraph (b)(10) of this section. Methane measurements shall be made on a dry basis.


(16) Calibration gas values shall be traceable to the National Institute for Standards and Testing (NIST), “Standard Reference Materials” (SRM’s). The analytical accuracy of the calibration gas values shall be within 2.0 percent of NIST gas standards.


(17) Span gas values shall be traceable to NIST SRM’s. The analytical accuracy of the span gas values shall be within 2.0 percent of NIST gas standards.


(18) Calibration or span gases for the CO and CO2 analyzers shall have purified nitrogen as a diluent. Calibration or span gases for the CH4 analyzer shall be CH4 with purified synthetic air or purified nitrogen as diluent.


(19) Calibration or span gases for the NOX analyzer shall be NO with a maximum NO2 concentration of 5 percent of the NO content. Purified nitrogen shall be the diluent.


(20) Zero-grade gases for the CO, CO2, CH4 , and NOX analyzers shall be either purified synthetic air or purified nitrogen.


(21) The allowable zero-grade gas (purified synthetic air or purified nitrogen) impurity concentrations shall not exceed ≤1ppm C, ≤1 ppm CO, ≤400 ppm CO2, and ≤0.1 ppm NO.


(22) The calibration and span gases may also be obtained by means of a gas divider. The accuracy of the mixing device must be such that the concentration of the diluted calibration gases are within 2 percent.


(c) Particulate sampling system shall be used in determining the particulate index. A schematic of a full flow (single dilution) particulate sampling system for testing under this subpart is shown in Figures E-3 and E-4.


(1) The dilution system shall meet the following parameters:


(i) Either a positive displacement pump (PDP) or a critical flow venturi (CFV) shall be used as the pump/mass measurement device shown in Figure E-3.


(ii) The total volume of the mixture of exhaust and dilution air shall be measured.


(iii) All parts of the system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, shall be designed to minimize deposition or alteration of the particulate.


(iv) All parts shall be made of electrically conductive materials that do not react with exhaust gas components.


(v) All parts shall be electrically grounded to prevent electrostatic effects.


(vi) Systems other than full flow systems may also be used provided they yield equivalent results where:


(A) A seven sample pair (or larger) correlation study between the system under consideration and a full flow dilution system shall be run concurrently.


(B) Correlation testing is to be performed at the same laboratory, test cell, and on the same engine.


(C) The equivalency criterion is defined as a ±5 percent agreement of the sample pair averages.


(2) The mass of particulate in the exhaust shall be collected by filtration. The exhaust temperature immediately before the primary particulate filter shall not exceed 125 °F (52.0 °C).


(3) Exhaust system backpressure shall not be artificially lowered by the PDP, CFV systems or dilution air inlet system. Static exhaust backpressure measured with the PDP or CFV system operating shall remain within ±0.44 inches Hg (1.5 kPa) of the static pressure measured without being connected to the PDP or CFV at identical engine speed and load.


(4) The gas mixture temperature shall be measured at a point immediately ahead of the pump or mass measurement device.


(i) Using PDP, the gas mixture temperature shall be maintained within ±10 °F (6.0 °C) of the average operating temperature observed during the test, when no flow compensation is used.


(ii) Flow compensation can be used provided that the temperature at the inlet to the PDP does not exceed 122 °F (50 °C).


(iii) Using CFV, the gas mixture temperature shall be maintained within ±20 °F (11 °C) of the average operating temperature observed during the test, when no flow compensation is used.


(5) The heat exchanger shall be of sufficient capacity to maintain the temperature within the limits required above and is optional if electronic flow compensation is used.


(6) When the temperature at the inlet of either the PDP or CFV exceeds the limits stated in either paragraphs (c)(4)(i) or (c)(4)(iii) of this section, an electronic flow compensation system shall be required for continuous measurement of the flow rate and control of the proportional sampling in the particulate sampling system.


(7) The flow capacity of the system shall be large enough to eliminate water condensation.




(8) The flow capacity of the PDP or CFV system using single dilution shall maintain the diluted exhaust at 125 °F (52.0 °C) or less immediately before the primary particulate filter.


(9) The flow capacity of the PDP or CFV system using a double dilution system shall be sufficient to maintain the diluted exhaust in the dilution tunnel at 375 °F (191 °C) or less at the sampling zone.


(10) The secondary dilution system shall provide sufficient secondary dilution air to maintain the double-diluted exhaust stream at 125 °F (52.0 °C) or less immediately before the primary particulate filter.


(11) The gas flow meters or the mass flow measurement instrumentation shall have a maximum error of the measured value within ±2 percent of reading.


(12) The dilution air shall have a temperature of 77 °F ±9 °F (25 °C ±5 °C), and be –


(i) Filtered at the air inlet; or


(ii) Sampled to determine background particulate levels, which can then be subtracted from the values measured in the exhaust stream.


(13) The dilution tunnel shall have the following specifications:


(i) Be small enough in diameter to cause turbulent flow (Reynolds number greater than 4,000) and of sufficient length to cause complete mixing of the exhaust and dilution air;


(ii) Be at least 3 inches (75 mm) in diameter; and


(iii) Be configured to direct the engine exhaust downstream at the point where it is introduced into the dilution tunnel for thorough mixing.


(14) The exhaust pipe length from the exit of the engine exhaust manifold or turbocharger outlet to the dilution tunnel shall not exceed a total length of 32 feet (10 m).


(i) When the exhaust pipe exceeds 12 feet (4 m), then all pipe in excess of 12 feet (4 m) shall be insulated with a radial thickness of at least 1.0 inch (25 mm) and the thermal conductivity of the insulating material shall be no greater than 0.1 W/mK measured at 752 °F (400 °C).


(ii) To reduce the thermal inertia of the exhaust pipe, the thickness to diameter ratio shall be 0.015 or less.


(iii) The use of flexible sections shall be limited to the length to diameter ratio of 12 or less.


(15) The particulate sample probe shall –


(i) Be installed in the dilution tunnel facing upstream, on the dilution tunnel centerline, and approximately 10 dilution tunnel diameters downstream of the point where the engine’s exhaust enters the dilution tunnel; and


(ii) Have 0.5 inches (12 mm) minimum inside diameter.


(16) The inlet gas temperature to the particulate sample pump or mass measurement device shall remain a constant temperature of ±5 °F (3.0 °C) if flow compensation is not used.


(17) The secondary dilution portion of the double dilution system shall have:


(i) A particulate transfer tube shall have a 0.5 inch (12 mm) minimum inside diameter not to exceed 40 inches (1020 mm) in length measured from the probe tip to the secondary dilution tunnel has:


(A) An inlet with the transfer tube facing upstream in the primary dilution tunnel, centerline, and approximately 10 dilution tunnel diameters downstream of the point where the engine’s exhaust enters the dilution tunnel.


(B) An outlet where the transfer tube exits on the centerline of the secondary tunnel and points downstream.


(ii) A secondary tunnel that has a minimum diameter of 3.0 inches (75 mm), and of sufficient length to provide a residence time of at least 0.25 seconds for the double-diluted sample.


(iii) Secondary dilution air supplied at a temperature of 77 °F ±9 °F (25 °C ±5 °C).


(iv) A primary filter holder located within 12.0 inches (300 mm) of the exit of the secondary tunnel.


(18) The particulate sampling filters shall –


(i) Be fluorocarbon-coated glass fiber filters or fluorocarbon-based (membrane) filters and have a 0.3 µm di-octylphthalate (DOP) collection efficiency of at least 95 percent at a gas face velocity between 35 and 80 cm/s.;


(ii) Have a minimum diameter of 1.85 inches (47 mm), 1.46 inches (37 mm) stain diameter;


(iii) Have a minimum filter loading ratio of 0.5mg/1075 mm
2 stain area for the single filter method.


(iv) Have minimum filter loading such that the sum of all eight (8) multiple filters is equal to the minimum loading value (mg) for a single filter multiplied by the square root of eight (8).


(v) Be sampled at the same time by a pair of filters in series (one primary and one backup filter) so that:


(A) The backup filter holder shall be located no more than 4 inches (100 mm) downstream of the primary filter holder.


(B) The primary and backup filters shall not be in contact with each other.


(C) The filters may be weighed separately or as a pair with the filters placed stain side to stain side.


(D) The single filter method incorporates a bypass system for passing the sample through the filters at the desired time.


(vi) Have a pressure drop increase between the beginning and end of the test of no more than 7.4 in Hg (25kPa).


(vii) Filters of identical quality shall be used when performing correlation tests specified in paragraph (c)(1)(vi) of this section.


(19) Weighing chamber specifications. (i) The temperature of the chamber (room) in which the particulate filters are conditioned and weighed shall be maintained to within 72 °F ±5 °F (22 °C ±3 °C) during all filter conditioning and weighing.


(ii) The humidity of the chamber (room) in which the particulate filters are conditioned and weighed shall be maintained to a dewpoint of 49 °F ±5 °F (9.5 °C ±3 °C) and a relative humidity of 45 percent ±8 percent during all filter conditioning and weighing.


(iii) The chamber (room) environment shall be free of any ambient contaminants (such as dust) that would settle on the particulate filters during their stabilization. This shall be determined as follows:


(A) At least two unused reference filters or reference filter pairs shall be weighed within four (4) hours of, but preferably at the same time as the sample filter (pair) weighings.


(B) The reference filters are to be the same size and material as the sample filters.


(C) If the average weight of reference filters (reference filter pairs) changes between sample filter weighings by more than ±5.0 percent (±7.5 percent for the filter pair respectively) of the recommended minimum filter loading in paragraphs (c)(18)(iii) or (c)(18)(iv) of this section, then all sample filters shall be discarded and the tests repeated.


(20) The analytical balance used to determine the weights of all filters shall have a precision (standard deviation) of 20 µg and resolution of 10 µg. For filters less than 70 mm diameter, the precision and resolution shall be 2 µg and 1 µg, respectively.


(21) All filters shall be neutralized to eliminate the effects of static electricity prior to weighing.


§ 7.87 Test to determine the maximum fuel-air ratio.

(a) Test procedure. (1) Couple the diesel engine to the dynamometer and connect the sampling and measurement devices specified in § 7.86.


(2) Prior to testing, zero and span the CO and NOX analyzers to the lowest analyzer range that will be used during this test.


(3) While running the engine, the following shall apply:


(i) The parameter for the laboratory atmospheric factor, fa, shall be: 0.98≤fa≤1.02;


(A) The equation is fa = ( 99/Ps) * ((Ta + 273)/298)
0.7 for a naturally aspirated and mechanically supercharged engines; or


(B) The equation is fa = (99/Ps)
0.7* ((Ta + 273)/298)
1.5 for a turbocharged engine with or without cooling of the intake air.



Where:

Ps = dry atmospheric pressure (kPa)

Ta = intake air temperature (°C)

(ii) The air inlet restriction shall be set within ±10 percent of the recommended maximum air inlet restriction as specified by the engine manufacturer at the engine operating condition giving maximum air flow to determine the concentration of CO as specified in paragraph (a)(6) of this section.


(iii) The exhaust backpressure restriction shall be set within ±10 percent of the maximum exhaust backpressure as specified by the engine manufacturer at the engine operating condition giving maximum rated horsepower to determine the concentrations of CO and NOX as specified in paragraph (a)(6)of this section.


(iv) The air inlet restriction shall be set within ±10 percent of a recommended clean air filter at the engine operating condition giving maximum air flow as specified by the engine manufacturer to determine the concentration of NOX as specified in paragraph (a)(6) of this section.


(4) The engine shall be at a steady-state condition when the exhaust gas samples are collected and other test data is measured.


(5) In a category A engine, 1.0 ±0.1 percent CH4 shall be injected into the engine’s intake air.


(6) Operate the engine at several speed/torque conditions to determine the concentrations of CO and NOX, dry basis, in the raw exhaust.


(b) Acceptable performance. The CO and NOX concentrations in the raw exhaust shall not exceed the limits specified in § 7.84(b) throughout the specified operational range of the engine.


§ 7.88 Test to determine the gaseous ventilation rate.

The test shall be performed in the order listed in Table E-2. The test for determination of the particulate index described in § 7.89 may be done simultaneously with this test.


(a) Test procedure. (1) Couple the diesel engine to the dynamometer and attach the sampling and measurement devices specified in § 7.86.


(2) A minimum time of 10 minutes is required for each test mode.


(3) CO, CO2, NOX, and CH4 analyzers shall be zeroed and spanned at the analyzer range to be used prior to testing.


(4) Run the engine.


(i) The parameter for fa shall be calculated in accordance with § 7.87(a)(3).


(ii) The air inlet and exhaust backpressure restrictions on the engine shall be set as specified in §§ 7.87(a)(3) (iii) and (iv).


(5) The engine shall be at a steady-state condition before starting the test modes.


(i) The output from the gas analyzers shall be measured and recorded with exhaust gas flowing through the analyzers a minimum of the last three (3) minutes of each mode.


(ii) To evaluate the gaseous emissions, the last 60 seconds of each mode shall be averaged.


(iii) A 1.0 ±0.1 percent CH4, by volume, shall be injected into the engine’s intake air for category A engines.


(iv) The engine speed and torque shall be measured and recorded at each test mode.


(v) The data required for use in the gaseous ventilation calculations specified in paragraph (a)(9) of this section shall be measured and recorded at each test mode.


(6) Operate the engine at each rated speed and horsepower rating requested by the applicant according to Table E-2 in order to measure the raw exhaust gas concentration, dry basis, of CO, CO2, NO, and NO2, and CH4– exhaust (category A engines only).


(i) Test speeds shall be maintained within ±1 percent of rated speed or ±3 RPM, which ever is greater, except for low idle which shall be within the tolerances established by the manufacturer.


(ii) The specified torque shall be held so that the average over the period during which the measurements are taken is within ±2 percent of the maximum torque at the test speed.


(7) The concentration of CH4 in the intake air shall be measured for category A engines.


Table E-2 – Gaseous Test Modes

Speed
Rated speed
Intermediate speed
Low-idle speed
% Torque
100
75
50
10
100
75
50
0

(8) After completion of the test modes, the following shall be done:


(i) Zero and span the analyzers at the ranges used during the test.


(ii) The gaseous emission test shall be acceptable if the difference in the zero and span results taken before the test and after the test are less than 2 percent.


(9) The gaseous ventilation rate for each exhaust gas contaminant shall be calculated as follows –


(i) The following abbreviations shall apply to both category A and category B engine calculations as appropriate:



cfm – Cubic feet per min (ft
3/min)

Exh – Exhaust

A – Air (lbs/hr)

H – Grains of water per lb. of dry intake air

J – Conversion factor

m – Mass flow rate (mass/hr)

TI – Intake air temperature (°F)

PCAir – Percent Air

PCCH4 – Percent CH4 (intake air)

UCH4 – Unburned CH4

PCECH4 – Percent Exhaust CH4

(ii) Exhaust gas flow calculation for category B engines shall be (m Exh) = (A) + (m fuel).


(iii) Fuel/air ratio for category B engines shall be (f/a) = (m fuel) / (A).


(iv) Methane flow through category A engines shall be determined by the following:


PCAir = 100−PCCH4

Y = (PCAir)(0.289) + (PCCH4)(0.16)

Z = (0.16)(PCCH4) ÷ Y

mCH4 = (A)(Z) ÷ (1−Z)

(v) Exhaust gas flow calculation for category A engines shall be (m Exh) = (A) + (m fuel) + (m CH4)


(vi) Unburned CH4 (lbs/hr) calculation for category A engines shall be mUCH4 = (m Exh)(0.0052)(PCECH4)


(vii) Fuel/air ratio for category A engines shall be (f/a) = ((m fuel) + (m CH4)−(m UCH4)) ÷ (A)


(viii) Conversion from dry to wet basis for both category A and category B engines shall be:


(NO wet basis) = (NO dry basis)(J)

(NO2 wet basis) = (NO2 dry basis)(J)

(CO2 wet basis) = (CO2 dry basis)(J)

(CO wet basis) = (CO dry basis)(10−4)(J)


Where:

J = (f/a)(−1.87) + (1 − (0.00022)(H))

(ix) NO and NO2 correction for humidity and temperature for category A and category B engines shall be:


(NO corr) = (NO wet basis) ÷ (E)

(NO2 corr) = (NO2 wet basis) ÷ (E)


Where:

E = 1.0 + (R)(H − 75) + (G)(TI − 77)

R = (f/a)(0.044) − (0.0038)

G = (f/a)(−0.116) + (0.0053)

(x) The calculations to determine the m of each exhaust gas contaminant in grams per hour at each test point shall be as follows for category A and category B engines:


(m NO) = (NO corr)(0.000470)(m Exh)

(m NO2) = (NO2 corr)(0.000720)(m Exh)

(m CO2) = (CO2 wet basis)(6.89)(m Exh)

(m CO) = (CO wet basis)(4.38)(m Exh)

(xi) The calculations to determine the ventilation rate for each exhaust gas contaminant at each test point shall be as follows for category A and category B engines:


(cfm NO) = (m NO)(K)

(cfm NO2) = (m NO2)(K)

(cfm CO2) = (m CO2)(K)

(cfm CO) = (m CO)(K)


Where:

K = 13,913.4/ (pollutant grams/mole) (pollutant dilution value specified in § 7.84(c)).

(b) The gaseous ventilation rate for each requested rated speed and horsepower shall be the highest ventilation rate calculated in paragraph (a)(9)(xi) of this section.


(1) Ventilation rates less than 20,000 cfm shall be rounded up to the next 500 cfm.


Example: 10,432 cfm shall be listed 10,500 cfm.


(2) Ventilation rates greater than 20,000 cfm shall be rounded up to the next 1,000 cfm.


Example: 26,382 cfm shall be listed 27,000 cfm.


[61 FR 55504, Oct. 25, 1996; 62 FR 34640, June 27, 1997]


§ 7.89 Test to determine the particulate index.

The test shall be performed in the order listed in Table E-3.


(a) Test procedure. (1) Couple the diesel engine to the dynamometer and connect the sampling and measurement devices specified in § 7.86.


(2) A minimum time of 10 minutes is required for each measuring point.


(3) Prior to testing, condition and weigh the particulate filters as follows:


(i) At least 1 hour before the test, each filter (pair) shall be placed in a closed, but unsealed, petri dish and placed in a weighing chamber (room) for stabilization.


(ii) At the end of the stabilization period, each filter (pair) shall be weighed. The reading is the tare weight.


(iii) The filter (pair) shall then be stored in a closed petri dish or a filter holder, both of which shall remain in the weighing chamber (room) until needed for testing.


(iv) The filter (pair) must be re-weighed if not used within 8 hours of its removal from the weighing chamber (room).


(4) Run the engine.


(i) The parameter for fa shall be calculated in accordance with § 7.87(a)(3).


(ii) The air inlet and exhaust backpressure restrictions on the engine shall be set as specified in §§ 7.87(a)(3) (iii) and (iv).


(iii) The dilution air shall be set to obtain a maximum filter face temperature of 125 °F (52 °C) or less at each test mode.


(iv) The total dilution ratio shall not be less than 4.


(5) The engine shall be at a steady state condition before starting the test modes.


(i) The engine speed and torque shall be measured and recorded at each test mode.


(ii) The data required for use in the particulate index calculation specified in paragraph (a)(9) of this section shall be measured and recorded at each test mode.


(6) A 1.0 ±0.1 percent CH4, by volume shall be injected into the engine’s intake air for category A engines.


(7) Operate the engine at each rated speed and horsepower rating requested by the applicant according to Table E-3 to collect particulate on the primary filter.


(i) One pair of single filters shall be collected or eight multiple filter pairs shall be collected.


(ii) Particulate sampling shall be started after the engine has reached a steady-state condition.


(iii) The sampling time required per mode shall be either a minimum of 20 seconds for the single filter method or a minimum of 60 seconds for the multiple filter method.


(iv) The minimum particulate loading specified in §§ 7.86(c)(18) (iii) or (iv) shall be done.


Table E-3 – Particulate Test Modes

Speed
Rated speed
Intermediate speed
Low-idle speed
% Torque
100
75
50
10
100
75
50
0
Weighting factor0.150.150.150.10.10.10.10.15

(v) Test speeds shall be maintained within ±percent of rated speed or ±3 RPM, which ever is greater, except for low idle which shall be within the tolerances set by the manufacturer.


(vi) The specified torque shall be held so that the average over the period during which the measurements are being taken is within ±2 percent of the maximum torque at the test speed.


(vii) The modal weighting factors (WF) given in Table E-3 shall be applied to the multiple filter method during the calculations as shown in paragraph (a)(9)(iii)(B) of this section.


(viii) For the single filter method, the modal WF shall be taken into account during sampling by taking a sample proportional to the exhaust mass flow for each mode of the cycle.


(8) After completion of the test, condition and weigh the particulate filters in the weighing chamber (room) as follows:


(i) Condition the filters for at least 1 hour, but not more than 80 hours.


(ii) At the end of the stabilization period, weigh each filter. The reading is the gross weight.


(iii) The particulate mass of each filter is its gross weight minus its tare weight.


(iv) The particulate mass (PF for the single filter method; PF,i for the multiple filter method) is the sum of the particulate masses collected on the primary and back-up filters.


(v) The test is void and must be rerun if the sample on the filter contacts the petri dish or any other surface.


(9) The particulate index for the mass particulate shall be calculated from the equations listed below –


(i) The following abbreviations shall be:



cfm – Cubic feet per min (ft
3 min)

PT – Particulate (gr/hr)

m mix – Diluted exhaust gas mass flow rate on wet basis (kg/hr)

m sample – Mass of the diluted exhaust sample passed through the particulate sampling filters (kg)

Pf – Particulate sample mass collected on a filter (mg) at each test mode as determined in Table E-3.

Kp – Humidity correction factor for particulate

WF – Weighting factor

i-Subscript denoting an individual mode, i = 1, . . . n

PI – Particulate Index (cfm)

(ii) When calculating ambient humidity correction for the particulate concentration (Pf part), the equation shall be:


Pfcorr = (Pf)(Kp)

Kp = 1 / (1 + 0.0133 * (H − 10.71))


Where:

Ha = humidity of the intake air, g water per kg dry air

Ha = (6.220 * Ra * pa) / (pB−pa − Ra * 10−2)

Ra = relative humidity of the intake air, %

pa = saturation vapor pressure of the intake air, kPa

pB = total barometric pressure, kPa

(iii) When the multiple filter method is used, the following equations shall be used.


(A) Mass of particulate emitted is calculated as follows:




(B) Determination of weighted particulate average is calculated as follows:




(C) Determination of particulate index for the mass particulate from the average of the test modes shall be calculated as follows:




(iv) When the single filter method is used, the following equations shall be used.


(A) Mass of particulate emitted:




Where:





(B) Determination of particulate index for the mass particulate from the average of the test modes shall be as follows:




(v) When the effective weighting factor, WFE,i, for each mode is calculated for the single filter method, the following shall apply.




(B) The value of the effective weighting factors shall be within ±0.005 (absolute value) of the weighting factors listed in Table E-3.


(b) A particulate index for each requested rated speed and horsepower shall be the value determined in paragraph (a)(9)(iii)(C) of this section for the multiple filter method or paragraph (a)(9)(iv)(B) of this section for the single filter method.


(1) Particulate indices less than 20,000 cfm shall be rounded up to the next 500 cfm. Example: 10,432 cfm shall be listed 10,500 cfm.


(2) Particulate indices greater than 20,000 cfm shall be rounded up to the nearest thousand 1,000 cfm. Example: 26,382 cfm shall be listed 27,000 cfm.


[61 FR 55504, Oct. 25, 1996; 62 FR 34640, June 27, 1997]


§ 7.90 Approval marking.

Each approved diesel engine shall be identified by a legible and permanent approval marking inscribed with the assigned MSHA approval number and securely attached to the diesel engine. The marking shall also contain the following information:


(a) Ventilation rate.


(b) Rated power.


(c) Rated speed.


(d) High idle.


(e) Maximum altitude before deration.


(f) Engine model number.


§ 7.91 Post-approval product audit.

Upon request by MSHA, but no more than once a year except for cause, the approval holder shall make a diesel engine available for audit at no cost to MSHA.


§ 7.92 New technology.

MSHA may approve a diesel engine that incorporates technology for which the requirements of this subpart are not applicable if MSHA determines that the diesel engine is as safe as those which meet the requirements of this subpart.


Subpart F – Diesel Power Packages Intended for Use in Areas of Underground Coal Mines Where Permissible Electric Equipment is Required


Source:61 FR 55518, Oct. 25, 1996, unless otherwise noted.

§ 7.95 Purpose and effective date.

Part 7, subpart A general provisions apply to subpart F. Subpart F establishes the specific requirements for MSHA approval of diesel power packages intended for use in approved equipment in areas of underground coal mines where electric equipment is required to be permissible. It is effective November 25, 1996.


§ 7.96 Definitions.

In addition to the definitions in subparts A and E of this part, the following definitions apply in this subpart.


Cylindrical joint. A joint comprised of two contiguous, concentric, cylindrical surfaces.


Diesel power package. A diesel engine with an intake system, exhaust system, and a safety shutdown system installed.


Dry exhaust conditioner. An exhaust conditioner that cools the exhaust gas without direct contact with water.


Exhaust conditioner. An enclosure, containing a cooling system, through which the exhaust gases pass.


Exhaust system. A system connected to the outlet of the diesel engine which includes, but is not limited to, the exhaust manifold, the exhaust pipe, the exhaust conditioner, the exhaust flame arrester, and any adapters between the exhaust manifold and exhaust flame arrester.


Fastening. A bolt, screw, or stud used to secure adjoining parts to prevent the escape of flame from the diesel power package.


Flame arrester. A device so constructed that flame or sparks from the diesel engine cannot propagate an explosion of a flammable mixture through it.


Flame arresting path (explosion-proof joint). Two or more adjoining or adjacent surfaces between which the escape of flame is prevented.


Flammable mixture. A mixture of methane or natural gas with normal air, that will propagate flame or explode when ignited.


Grade. The slope of an incline expressed as a percent.


High idle speed. The maximum no load speed specified by the engine manufacturer.


Intake system. A system connected to the inlet of the diesel engine which includes, but is not limited to, the intake manifold, the intake flame arrester, the emergency intake air shutoff device, the air cleaner, and all piping and adapters between the intake manifold and air cleaner.


Plane joint. A joint comprised of two adjoining surfaces in parallel planes.


Safety shutdown system. A system which, in response to signals from various safety sensors, recognizes the existence of a potential hazardous condition and automatically shuts off the fuel supply to the engine.


Step (rabbet) joint. A joint comprised of two adjoining surfaces with a change or changes in direction between its inner and outer edges. A step joint may be composed of a cylindrical portion and a plane portion or of two or more plane portions.


Threaded joint. A joint consisting of a male- and female-threaded member, both of which are the same type and gauge.


Wet exhaust conditioner. An exhaust conditioner that cools the exhaust gas through direct contact with water, commonly called a water scrubber.


§ 7.97 Application requirements.

(a) An application for approval of a diesel power package shall contain sufficient information to document compliance with the technical requirements of this subpart and include: drawings, specifications, and descriptions with dimensions (including tolerances) demonstrating compliance with the technical requirements of § 7.98. The specifications and descriptions shall include the materials of construction and quantity. These shall include the following –


(1) A general arrangement drawing showing the diesel power package and the location and identification of the intake system, exhaust system, safety shutdown system sensors, flame arresters, exhaust conditioner, emergency intake air shutoff device, automatic fuel shutoff device and the engine.


(2) Diesel engine specifications including the MSHA approval number, the engine manufacturer, the engine model number, and the rated speed, rated horsepower, and fuel rate.


(3) A drawing(s) which includes the fan blade material specifications, the location and identification of all water-cooled components, coolant lines, radiator, surge tank, temperature sensors, and orifices; arrows indicating proper flow direction; the height relationship of water-cooled components to the surge tank; and the proper procedure for filling the cooling system.


(4) A drawing(s) showing the relative location, identification of components, and design of the safety shutdown system.


(5) Specific component identification, or specific information including detail drawings that identify the characteristics of the cooling system and safety shutdown system that ensures compliance with the technical requirements.


(6) Detail drawings of gaskets used to form flame-arresting paths.


(7) An assembly drawing showing the location and identification of all intake system components from the air cleaner to the engine head.


(8) An assembly drawing showing the location and identification of all exhaust system components from the engine head to the exhaust outlet.


(9) Detail drawings of those intake and exhaust system components identified in paragraphs (a)(7) and (a)(8) of this section that ensure compliance with the technical requirements. An exhaust conditioner assembly drawing shall be provided showing the location, dimensions, and identification of all internal parts, exhaust inlet and outlet, sensors, and the exhaust gas path through the exhaust conditioner. If a wet exhaust conditioner is used, the exhaust conditioner assembly drawing must also show the location, dimensions, and identification of the fill port, drain port, low water check port; high or normal operating water level; minimum allowable low water level; and the maximum allowable grade that maintains explosion-proof operations.


(10) A power package checklist which shall consist of a list of specific features that must be checked and tests that must be performed to determine if a previously approved diesel power package is in approved condition. Test procedures shall be specified in sufficient detail to allow the evaluation to be made without reference to other documents. Illustrations shall be used to fully identify the approved configuration of the diesel power package.


(11) Information showing that the electrical systems and components meet the requirements of § 7.98.


(12) A drawing list consisting of a complete list of those drawings and specifications which show the details of the construction and design of the diesel power package.


(b) Composite drawings specifying the required construction details may be submitted instead of the individual drawings in paragraph (a) of this section.


(c) All documents shall be titled, dated, numbered, and include the latest revision.


(d) When all testing has been completed, the following information shall be submitted and become part of the approval documentation:


(1) The settings of any adjustable devices used to meet the performance requirements of this subpart.


(2) The coolant temperature sensor setting and exhaust gas temperature sensor setting used to meet the performance requirements of this subpart.


(3) The minimum allowable low water level and the low water sensor setting used to meet the performance requirements of this subpart for systems using a wet exhaust conditioner as the exhaust flame arrester.


(4) The maximum grade on which the wet exhaust conditioner can be operated retaining the flame arresting characteristics.


(5) A finalized version of the power package checklist.


§ 7.98 Technical requirements.

(a) The diesel power package shall use a category A diesel engine approved under subpart E of this part with the following additional requirements:


(1) A hydraulic, pneumatic, or other mechanically actuated starting mechanism. Other means of starting shall be evaluated in accordance with the provisions of § 7.107.


(2) If an air compressor is provided, the intake air line shall be connected to the engine intake system between the air cleaner and the flame arrester. If the air compressor’s inlet air line is not connected to the engine’s intake system, it shall have an integral air filter.


(b) The temperature of any external surface of the diesel power package shall not exceed 302 °F (150 °C).


(1) Diesel power package designs using water jacketing to meet this requirement shall be tested in accordance with § 7.101.


(2) Diesel power packages using other techniques will be evaluated under the provisions of § 7.107.


(3) When using water-jacketed components, provisions shall be made for positive circulation of coolant, venting of the system to prevent the accumulation of air pockets, and effective activation of the safety shutdown system before the temperature of the coolant in the jackets exceeds the manufacturer’s specifications or 212 °F (100 °C), whichever is lower.


(c) External rotating parts shall not be constructed of aluminum alloys containing more than 0.6 percent magnesium.


(d) If nonmetallic rotating parts are used, they shall be provided with a means to prevent an accumulation of static electricity. Static conducting materials shall have a total resistance of 1 megohm or less, measured with an applied potential of 500 volts or more. Static conducting materials having a total resistance greater than 1 megohm will be evaluated under the provisions of § 7.107.


(e) All V-belts shall be static conducting and have a resistance not exceeding 6 megohms, when measured with a direct current potential of 500 volts or more.


(f) The engine crankcase breather shall not be connected to the air intake system of the engine. The discharge from the breather shall be directed away from hot surfaces of the engine and exhaust system.


(g) Electrical components on diesel power packages shall be certified or approved by MSHA under parts 7, 18, 20, and 27 of this chapter.


(h) Electrical systems on diesel power packages consisting of electrical components, interconnecting wiring, and mechanical and electrical protection shall meet the requirements of parts 7, 18, and 27 of this chapter, as applicable.


(i) The diesel power package shall be equipped with a safety shutdown system which will automatically shut off the fuel supply and stop the engine in response to signals from sensors indicating –


(1) The coolant temperature limit specified in paragraph (b) of this section;


(2) The exhaust gas temperature limit specified in paragraph (s)(4) of this section;


(3) The minimum allowable low water level, for a wet exhaust conditioner, as established by tests in § 7.100. Restarting of the engine shall be prevented until the water level in the wet exhaust conditioner has been replenished above the minimum allowable low water level; and


(4) The presence of other safety hazards such as high methane concentration, actuation of the fire suppression system, etc., if such sensors are included in the safety shutdown system.


(j) The safety shutdown system shall have the following features:


(1) A means to automatically disable the starting circuit and prevent engagement of the starting mechanism while the engine is running, or a starting mechanism constructed of nonsparking materials.


(2) If the design of the safety shutdown system requires that the lack of engine oil pressure must be overridden to start the engine, the override shall not be capable of overriding any of the safety shutdown sensors specified in paragraph (i) of this section.


(k) The diesel power package shall be explosion-proof as determined by the tests set out in § 7.100.


(l) Engine joints that directly or indirectly connect the combustion chamber to the surrounding atmosphere shall be explosion-proof in accordance with paragraphs (m) through (q) of this section and § 7.100. This paragraph does not apply to the following:


(1) Pistons to piston rings;


(2) Pistons to cylinder walls;


(3) Piston rings to cylinder walls;


(4) Cylinder head to cylinder block;


(5) Valve stem to valve guide; or


(6) Injector body to cylinder head.


(m) Each segment of the intake system and exhaust system required to provide explosion-proof features shall be constructed of metal and designed to withstand a minimum internal pressure equal to four times the maximum pressure observed in that segment in tests under § 7.100 or a pressure of 150 psig, whichever is less. Castings shall be free from blowholes.


(n) Welded joints forming the explosion-proof intake and exhaust systems shall be continuous and gas-tight. At a minimum, they shall be made in accordance with American Welding Society Standard D14.4-77 or meet the test requirements of § 7.104 with the internal pressure equal to four times the maximum pressure observed in tests under § 7.100 or a pressure of 150 psig, whichever is less.


(o) Flexible connections shall be permitted in segments of the intake and exhaust systems required to provide explosion-proof features, provided that failure of the connection activates the safety shutdown system before the explosion-proof characteristics are lost.


(p) Flame-arresting paths in the intake and exhaust systems shall be formed either by –


(1) Flanged metal to metal joints meeting the requirements of paragraph (q) of this section; or


(2) Metal flanges fitted with metal gaskets and meeting the following requirements:


(i) Flat surfaces between bolt holes that form any part of a flame-arresting path shall be planed to within a maximum deviation of one-half the maximum clearance specified in paragraph (q)(7) of this section. All metal surfaces forming a flame-arresting path shall be finished during the manufacturing process to not more than 250 microinches.


(ii) A means shall be provided to ensure that fastenings maintain the tightness of joints. The means provided shall not lose its effectiveness through repeated assembly and disassembly.


(iii) Fastenings shall be as uniform in size as practicable to preclude improper assembly.


(iv) Holes for fastenings shall not penetrate to the interior of an intake or exhaust system and shall be threaded to ensure that all specified bolts or screws will not bottom even if the washers are omitted.


(v) Fastenings used for joints of flame-arresting paths on intake or exhaust systems shall be used only for attaching parts that are essential in maintaining the explosion-proof integrity. They shall not be used for attaching brackets or other parts.


(vi) The minimum thickness of material for flanges shall be
1/2-inch, except that a final thickness of
7/16-inch is allowed after machining rolled plate.


(vii) The maximum fastening spacing shall be 6 inches.


(viii) The minimum diameter of fastenings shall be
3/8-inch, except smaller diameter fastenings may be used if the joint first meets the requirements of the static pressure test in § 7.104, and the explosion test in § 7.100.


(ix) The minimum thread engagement of fastenings shall be equal to or greater than the nominal diameter of the fastenings specified, or the intake or exhaust system must meet the test requirements of the explosion tests in § 7.100 and the static pressure test in § 7.104.


(x) The minimum contact surface of gaskets forming flame-arresting paths shall be
3/8-inch, and the thickness of the gaskets shall be no greater than
1/16-inch. The minimum distance from the interior edge of a gasket to the edge of a fastening hole shall be
3/8-inch. The gaskets shall be positively positioned, and a means shall be provided to preclude improper installation. When the joint is completely assembled, it shall be impossible to insert a 0.0015-inch thickness gauge to a depth exceeding
1/8-inch between the gasket and mating flanges. Other gasket designs shall be evaluated in accordance with § 7.107.


(q) The following construction requirements shall apply to flame-arresting paths formed without gaskets:


(1) Flat surfaces between fastening holes that form any part of a flame-arresting path shall be planed to within a maximum deviation of one-half the maximum clearance specified in paragraph (q)(7) of this section. All metal surfaces forming a flame-arresting path shall be finished during the manufacturing process to not more than 250 microinches. A thin film of nonhardening preparation to inhibit rusting may be applied to these finished metal surfaces, as long as the final surface can be readily wiped free of any foreign materials.


(2) A means shall be provided to ensure that fastenings maintain the tightness of joints. The means provided shall not lose its effectiveness through repeated assembly and disassembly.


(3) Fastenings shall be as uniform in size as practicable to preclude improper assembly.


(4) Holes for fastenings shall not penetrate to the interior of an intake or exhaust system and shall be threaded to ensure that all specified bolts or screws will not bottom even if the washers are omitted.


(5) Fastenings used for joints of flame-arresting paths on intake or exhaust systems shall be used only for attaching parts that are essential in maintaining the explosion-proof integrity. They shall not be used for attaching brackets or other parts.


(6) The flame-arresting path of threaded joints shall conform to the requirements of paragraph (q)(7) of this section.


(7) Intake and exhaust systems joints shall meet the specifications set out in Table F-1.


Table F-1 – Dimensional Requirements for Explosion-Proof Intake and Exhaust System Joints

Minimum thickness of material for flanges
1/2
1
Minimum width of joint; all in one plane1″
Maximum clearance; joint all in one plane0.004″
Minimum width of joint, portions of which are different planes; cylinders or equivalent
3/4
2
Maximum clearances; joint in two or more planes, cylinders or equivalent:
Portion perpendicular to plane0.008″
3
Plane portion0.006″
Maximum fastening
4 spacing; joints all in one plane
5
6″
Maximum fastening spacing; joints, portions of which are in different planes8″
Minimum diameter of fastening (without regard to type of joint)
6

3/8
Minimum thread engagement of fastening
7

3/8
Maximum diametrical clearance between fastening body and unthreaded holes through which it passes
8 9 10

1/16
Minimum distance from interior of the intake or exhaust system to the edge of a fastening hole:
11
Joint-minimum width 1″
7/16
8 12
Shafts centered by ball or roller bearings:
Minimum length of flame-arresting path1″
Maximum diametrical clearance0.030″
Other cylindrical joints:
Minimum length of flame-arresting path1″
Maximum diametrical clearance0.010″


1
1/16-inch less is allowable for machining rolled plate.


2 If only two planes are involved, neither portion of a joint shall be less than
1/8-inch wide, unless the wider portion conforms to the same requirements as those for a joint that is all in one plane. If more than two planes are involved (as in labyrinths or tongue-in-groove joints), the combined lengths of those portions having prescribed clearances are considered.


3 The allowable diametrical clearance is 0.008-inch when the portion perpendicular to the plane portion is
1/4-inch or greater in length. If the perpendicular portion is more than
1/8-inch but less than
1/4-inch wide, the diametrical clearance shall not exceed 0.006-inch.


4 Studs, when provided, shall bottom in blind holes, be completely welded in place, or have the bottom of the hole closed with a plug secured by weld or braze. Fastenings shall be provided at all corners.


5 The requirements as to diametrical clearance around the fastening and minimum distance from the fastening hole to the inside of the intake or exhaust system apply to steel dowel pins. In addition, when such pins are used, the spacing between centers of the fastenings on either side of the pin shall not exceed 5 inches.


6 Fastening diameters smaller than specified may be used if the joint or assembly meets the test requirements of § 7.104.


7 Minimum thread engagement shall be equal to or greater than the nominal diameter of the fastening specified, or the intake or exhaust system must meet the test requirements of § 7.104.


8 The requirements as to diametrical clearance around the fastening and minimum distance from the fastening hole to the inside of the intake or exhaust system apply to steel dowel pins. In addition, when such pins are used, the spacing between centers of the fastenings on either side of the pin shall not exceed 5 inches.


9 This maximum clearance only applies when the fastening is located within the flame-arresting path.


10 Threaded holes for fastenings shall be machined to remove burrs or projections that affect planarity of a surface forming a flame-arresting path.


11 Edge of the fastening hole shall include any edge of any machining done to the fastening hole, such as chamfering.


12 If the diametrical clearance for fastenings does not exceed
1/32-inch, then the minimum distance shall be
1/4-inch.


(r) Intake system. (1) The intake system shall include a device between the air cleaner and intake flame arrester, operable from the equipment operator’s compartment, to shut off the air supply to the engine for emergency purposes. Upon activation, the device must operate immediately and the engine shall stop within 15 seconds.


(2) The intake system shall include a flame arrester that will prevent an explosion within the system from propagating to a surrounding flammable mixture when tested in accordance with the explosion tests in § 7.100. The flame arrester shall be located between the air cleaner and the intake manifold and shall be attached so that it can be removed for inspection or cleaning. The flame arrester shall be constructed of corrosion-resistant metal and meet the following requirements:


(i) Two intake flame arrester designs, the spaced-plate type and the crimped ribbon type, will be tested in accordance with the requirements of § 7.100. Variations to these designs or other intake flame arrester designs will be evaluated under the provisions of § 7.107.


(ii) In flame arresters of the spaced-plate type, the thickness of the plates shall be at least 0.125-inch; spacing between the plates shall not exceed 0.018-inch; and the flame-arresting path formed by the plates shall be at least 1 inch wide. The unsupported length of the plates shall be short enough that permanent deformation resulting from explosion tests shall not exceed 0.002-inch. The plates and flame arrester housing shall be an integral unit which cannot be disassembled.


(iii) In flame arresters of the crimped ribbon type, the dimensions of the core openings shall be such that a plug gauge 0.018-inch in diameter shall not pass through, and the flame-arresting path core thickness shall be at least 1 inch. The core and flame arrester housing shall be an integral unit which cannot be disassembled.


(3) The intake system shall be designed so that improper installation of the flame arrester is impossible.


(4) The intake system shall include an air cleaner service indicator. The air cleaner shall be installed so that only filtered air will enter the flame arrester. The air cleaner shall be sized and the service indicator set in accordance with the engine manufacturer’s recommendations. Unless the service indicator is explosion-proof, it shall be located between the air cleaner and flame arrester, and the service indicator setting shall be reduced to account for the additional restriction imposed by the flame arrester.


(5) The intake system shall include a connection between the intake flame arrester and the engine head for temporary attachment of a device to indicate the total vacuum in the system. This opening shall be closed by a plug or other suitable device that is sealed or locked in place except when in use.


(s) Exhaust system. (1) The exhaust system shall include a flame arrester that will prevent propagation of flame or discharge of glowing particles to a surrounding flammable mixture. The flame arrester shall be constructed of corrosion-resistant metal.


(i) If a mechanical flame arrester is used, it shall be positioned so that only cooled exhaust gas at a maximum temperature of 302 °F (150 °C) will be discharged through it.


(ii) If a mechanical flame arrester of the spaced-plate type is used, it must meet the requirements of paragraph (r)(2)(ii) of this section and the test requirements of § 7.100. Variations to the spaced-plate flame arrester design and other mechanical flame arrester designs shall be evaluated under the provisions of § 7.107. The flame arrester shall be designed and attached so that it can be removed for inspection and cleaning.


(2) The exhaust system shall allow a wet exhaust conditioner to be used as the exhaust flame arrester provided that the explosion tests of § 7.100 demonstrate that the wet exhaust conditioner will arrest flame. When used as a flame arrester, the wet exhaust conditioner shall be equipped with a sensor to automatically activate the safety shutdown system at or above the minimum allowable low water level established by § 7.100. Restarting of the engine shall be prevented until the water supply in the wet exhaust conditioner has been replenished above the minimum allowable low water level. All parts of the wet exhaust conditioner and associated components that come in contact with contaminated exhaust conditioner water shall be constructed of corrosion-resistant material. The wet exhaust conditioner shall include a means for verifying that the safety shutdown system operates at the proper water level. A means shall be provided for draining and cleaning the wet exhaust conditioner. The final exhaust gas temperature at discharge from the wet exhaust conditioner shall not exceed 170 °F (76 °C) under test conditions specified in § 7.102. A sensor shall be provided that activates the safety shutdown system before the exhaust gas temperature at discharge from the wet exhaust conditioner exceeds 185 °F (85 °C) under test conditions specified in § 7.103(a)(4).


(3) The exhaust system shall be designed so that improper installation of the flame arrester is impossible.


(4) The exhaust system shall provide a means to cool the exhaust gas and prevent discharge of glowing particles.


(i) When a wet exhaust conditioner is used to cool the exhaust gas and prevent the discharge of glowing particles, the temperature of the exhaust gas at the discharge from the exhaust conditioner shall not exceed 170 °F (76 °C) when tested in accordance with the exhaust gas cooling efficiency test in § 7.102. A sensor shall be provided that activates the safety shutdown system before the exhaust gas temperature at discharge from the wet exhaust conditioner exceeds 185 °F (85 °C) when tested in accordance with the safety system controls test in § 7.103. All parts of the wet exhaust conditioner and associated components that come in contact with contaminated exhaust conditioner water shall be constructed of corrosion-resistant material.


(ii) When a dry exhaust conditioner is used to cool the exhaust gas, the temperature of the exhaust gas at discharge from the diesel power package shall not exceed 302 °F (150 °C) when tested in accordance with the exhaust gas cooling efficiency test of § 7.102. A sensor shall be provided that activates the safety shutdown system before the exhaust gas exceeds 302 °F (150 °C) when tested in accordance with the safety system control test in § 7.103. A means shall be provided to prevent the discharge of glowing particles, and it shall be evaluated under the provisions of § 7.107.


(5) Other means for cooling the exhaust gas and preventing the propagation of flame or discharge of glowing particles shall be evaluated under the provisions of § 7.107.


(6) There shall be a connection in the exhaust system for temporary attachment of a device to indicate the total backpressure in the system and collection of exhaust gas samples. This opening shall be closed by a plug or other suitable device that is sealed or locked in place except when in use.


[61 FR 55518, Oct. 25, 1996, 62 FR 34640, 34641, June 27, 1997]


§ 7.99 Critical characteristics.

The following critical characteristics shall be inspected or tested on each diesel power package to which an approval marking is affixed:


(a) Finish, width, planarity, and clearances of surfaces that form any part of a flame-arresting path.


(b) Thickness of walls and flanges that are essential in maintaining the explosion-proof integrity of the diesel power package.


(c) Size, spacing, and tightness of fastenings.


(d) The means provided to maintain tightness of fastenings.


(e) Length of thread engagement on fastenings and threaded parts that ensure the explosion-proof integrity of the diesel power package.


(f) Diesel engine approval marking.


(g) Fuel rate setting to ensure that it is appropriate for the intended application, or a warning tag shall be affixed to the fuel system notifying the purchaser of the need to make proper adjustments.


(h) Material and dimensions of gaskets that are essential in maintaining the explosion-proof integrity of the diesel power package.


(i) Dimensions and assembly of flame arresters.


(j) Materials of construction to ensure that the intake system, exhaust system, cooling fans, and belts have been fabricated from the required material.


(k) Proper interconnection of the coolant system components and use of specified components.


(l) Proper interconnection of the safety shutdown system components and use of specified components.


(m) All plugs and covers to ensure that they are tightly installed.


(n) The inspections and tests described in the diesel power package checklist shall be performed and all requirements shall be met.


§ 7.100 Explosion tests.

(a) Test procedures. (1) Prepare to test the diesel power package as follows:


(i) Perform a detailed check of parts against the drawings and specifications submitted under § 7.97 to determine that the parts and drawings agree.


(ii) Remove all parts that do not contribute to the operation or ensure the explosion-proof integrity of the diesel power package such as the air cleaner and exhaust gas dilution system.


(iii) Fill coolant system fluid and engine oil to the engine manufacturer’s recommended levels.


(iv) Interrupt fuel supply to the injector pump.


(v) Establish a preliminary low water level for systems using the wet exhaust conditioner as a flame arrester.


(2) Perform static and dynamic tests of the intake system as follows:


(i) Install the diesel power package in an explosion test chamber which is large enough to contain the complete diesel power package. The chamber must be sufficiently darkened and provide viewing capabilities of the flame-arresting paths to allow observation during testing of any discharge of flame or ignition of the flammable mixture surrounding the diesel power package. Couple the diesel power package to an auxiliary drive mechanism. Attach a pressure measuring device, a temperature measuring device, and an ignition source to the intake system. The pressure measuring device shall be capable of indicating the peak pressure accurate to ±1 pound-per-square inch gauge (psig) at 100 psig static pressure and shall have a frequency response of 40 Hertz or greater. The ignition source shall be an electric spark with a minimum energy of 100 millijoules. The ignition source shall be located immediately adjacent to the intake manifold and the pressure and temperature devices shall be located immediately adjacent to the flame arrester.


(ii) For systems using the wet exhaust conditioner as an exhaust flame arrester, fill the exhaust conditioner to the specified high or normal operating water level.


(iii) Fill the test chamber with a mixture of natural gas and air or methane and air. If natural gas is used, the content of combustible hydrocarbons shall total at least 98.0 percent, by volume, with the remainder being inert. At least 80.0 percent, by volume, of the gas shall be methane. For all tests, the methane or natural gas concentration shall be 8.5 ±1.8 percent, by volume, and the oxygen concentration shall be no less than 18 percent, by volume.


(iv) Using the auxiliary drive mechanism, motor the engine to fill the intake and exhaust systems with the flammable mixture. The intake system, exhaust system, and test chamber gas concentration shall not differ by more than ±0.3 percent, by volume, at the time of ignition.


(v) For static tests, stop the engine, actuate the ignition source, and observe the peak pressure. The peak pressure shall not exceed 110 psig. If the peak pressure exceeds 110 psig, construction changes shall be made that result in a reduction of pressure to 110 psig or less, or the system shall be tested in accordance with the static pressure test of § 7.104 with the pressure parameter replaced with a static pressure of twice the highest value recorded.


(vi) If the peak pressure does not exceed 110 psig or if the system meets the static pressure test requirements of this section and there is no discharge of visible flames or glowing particles or ignition of the flammable mixture in the chamber, a total of 20 tests shall be conducted in accordance with the explosion test specified above.


(vii) For dynamic tests, follow the same procedures for static tests, except actuate the ignition source while motoring the engine. Forty dynamic tests shall be conducted at two speeds, twenty at 1800 ±200 RPM and twenty at 1000 ±200 RPM. Under some circumstances, during dynamic testing the flammable mixture may continue to burn within the diesel power package after ignition. This condition can be recognized by the presence of a rumbling noise and a rapid increase in temperature. This can cause the flame-arrester to reach temperatures which can ignite the surrounding flammable mixture. Ignition of the flammable mixture in the test chamber under these circumstances does not constitute failure of the flame arrester. However; if this condition is observed, the test operator should immediately stop the engine and allow components to cool to prevent damage to the components.


(3) Perform static and dynamic tests of the exhaust system as follows:


(i) Prepare the diesel power package for explosion tests according to § 7.100(a)(2)(i) as follows:


(A) Install the ignition source immediately adjacent to the exhaust manifold.


(B) Install pressure measuring devices in each segment as follows: immediately adjacent to the exhaust conditioner inlet; in the exhaust conditioner; and immediately adjacent to the flame arrester, if applicable.


(C) Install a temperature device immediately adjacent to the exhaust conditioner inlet.


(ii) If the exhaust system is provided with a spaced-plate flame arrester in addition to an exhaust conditioner, explosion tests of the exhaust system shall be performed as described for the intake system in accordance with this section. Water shall not be present in a wet exhaust conditioner for the tests.


(iii) If the wet exhaust conditioner is used as the exhaust flame arrester, explosion testing of this type of system shall be performed as described for the intake system in accordance with this section with the following modifications:


(A) Twenty static tests, twenty dynamic tests at 1800 ±200 RPM, and twenty dynamic tests at 1000 ±200 RPM shall be conducted at 2 inches below the minimum allowable low water level. All entrances in the wet exhaust conditioner which do not form explosion-proof joints shall be opened. These openings may include lines which connect the reserve water supply to the wet exhaust conditioner, insert flanges, float flanges, and cover plates. These entrances are opened during this test to verify that they are not flame paths.


(B) Twenty static tests, twenty dynamic tests at 1800 ±200 RPM, and twenty dynamic tests at 1000 ±200 RPM shall be conducted at 2 inches below the minimum allowable low water level. All entrances in the wet exhaust conditioner (except the exhaust conditioner outlet) which do not form explosion-proof joints shall be closed. These openings are closed to simulate normal operation.


(C) Twenty static tests, twenty dynamic tests at 1800 ±200 RPM, and twenty dynamic tests at 1000 ±200 RPM shall be conducted at the specified high or normal operating water level. All entrances in the wet exhaust conditioner which do not form explosion-proof joints shall be opened.


(D) Twenty static tests, twenty dynamic tests at 1800 ±200 RPM, and twenty dynamic tests at 1000 ±200 RPM shall be conducted at the specified high or normal operating water level. All entrances in the wet exhaust conditioner (except the exhaust conditioner outlet) which do not form explosion-proof joints shall be closed.


(iv) After successful completion of the explosion tests of the exhaust system, the minimum allowable low water level, for a wet exhaust conditioner used as the exhaust flame arrester, shall be determined by adding two inches to the lowest water level that passed the explosion tests.


(v) A determination shall be made of the maximum grade on which the wet exhaust conditioner can be operated retaining the flame-arresting characteristics.


(b) Acceptable performance. The explosion tests shall not result in any of the following –


(1) Discharge of flame or glowing particles.


(2) Visible discharge of gas through gasketed joints.


(3) Ignition of the flammable mixture in the test chamber.


(4) Rupture of any part that affects the explosion-proof integrity.


(5) Clearances, in excess of those specified in this subpart, along accessible flame-arresting paths, following any necessary retightening of fastenings.


(6) Pressure exceeding 110 psig, unless the intake system or exhaust system has withstood a static pressure of twice the highest value recorded in the explosion tests of this section following the static pressure test procedures of § 7.104.


(7) Permanent distortion of any planar surface of the diesel power package exceeding 0.04-inches/linear foot.


(8) Permanent deformation exceeding 0.002-inch between the plates of spaced-plate flame arrester designs.


[61 FR 55518, Oct. 25, 1996; 62 FR 34641, June 27, 1997]


§ 7.101 Surface temperature tests.

The test for determination of exhaust gas cooling efficiency described in § 7.102 may be done simultaneously with this test.


(a) Test procedures. (1) Prepare to test the diesel power package as follows:


(i) Perform a detailed check of parts against the drawings and specifications submitted to MSHA under compliance with § 7.97 to determine that the parts and drawings agree.


(ii) Fill the coolant system with a mixture of equal parts of antifreeze and water, following the procedures specified in the application, § 7.97(a)(3).


(iii) If a wet exhaust conditioner is used to cool the exhaust gas, fill the exhaust conditioner to the high or normal operating water level and have a reserve water supply available, if applicable.


(2) Tests shall be conducted as follows:


(i) The engine shall be set to the rated horsepower specified in § 7.97(a)(2).


(ii) Install sufficient temperature measuring devices to determine the location of the highest coolant temperature. The temperature measuring devices shall be accurate to ±4 °F (±2 °C).


(iii) Operate the engine at rated horsepower and with 0.5 ±0.1 percent, by volume, of methane in the intake air mixture until all parts of the engine, exhaust coolant system, and other components reach their respective equilibrium temperatures. The liquid fuel temperature into the engine shall be maintained at 100 °F (38 °C) ±10 °F (6 °C) and the intake air temperature shall be maintained at 70 °F (21 °C) ±5 °F (3 °C).


(iv) Increase the coolant system temperatures until the highest coolant temperature is 205 °F to 212 °F (96 °C to 100 °C), or to the maximum temperature specified by the applicant, if lower.


(v) After all coolant system temperatures stabilize, operate the engine for 1 hour.


(vi) The ambient temperature shall be between 50 °F (10 °C) and 104 °F (40 °C) throughout the tests.


(b) Acceptable performance. The surface temperature of any external surface of the diesel power package shall not exceed 302 °F (150 °C) during the test.


§ 7.102 Exhaust gas cooling efficiency test.

(a) Test procedures. (1) Follow the procedures specified in § 7.101(a).


(2) Install a temperature measuring device to measure the exhaust gas temperature at discharge from the exhaust conditioner. The temperature measuring device shall be accurate to ±4 °F (±2 °C).


(3) Determine the exhaust gas temperature at discharge from the exhaust conditioner before the exhaust gas is diluted with air.


(b) Acceptable performance. (1) The exhaust gas temperature at discharge from a wet exhaust conditioner before the exhaust gas is diluted with air shall not exceed 170 °F (76 °C).


(2) The exhaust gas temperature at discharge from a dry exhaust conditioner before the gas is diluted with air shall not exceed 302 °F (150 °C).


§ 7.103 Safety system control test.

(a) Test procedures. (1) Prior to testing, perform the tasks specified in § 7.101(a)(1) and install sufficient temperature measuring devices to measure the highest coolant temperature and exhaust gas temperature at discharge from the exhaust conditioner. The temperature measuring devices shall be accurate to ±4 °F (±2 °C).


(2) Determine the effectiveness of the coolant system temperature shutdown sensors which will automatically activate the safety shutdown system and stop the engine before the coolant temperature in the cooling jackets exceeds manufacturer’s specifications or 212 °F (100 °C), whichever is lower, by operating the engine and causing the coolant in the cooling jackets to exceed the specified temperature.


(3) For systems using a dry exhaust gas conditioner, determine the effectiveness of the temperature sensor in the exhaust gas stream which will automatically activate the safety shutdown system and stop the engine before the cooled exhaust gas temperature exceeds 302 °F (150 °C), by operating the engine and causing the cooled exhaust gas to exceed the specified temperature.


(4) For systems using a wet exhaust conditioner, determine the effectiveness of the temperature sensor in the exhaust gas stream which will automatically activate the safety shutdown system and stop the engine before the cooled exhaust gas temperature exceeds 185 °F (85 °C), with the engine operating at a high idle speed condition. Temporarily disable the reserve water supply, if applicable, and any safety shutdown system control that might interfere with the evaluation of the operation of the exhaust gas temperature sensor. Prior to testing, set the water level in the wet exhaust conditioner to a level just above the minimum allowable low water level. Run the engine until the exhaust gas temperature sensor activates the safety shutdown system and stops the engine.


(5) For systems using a wet exhaust conditioner as an exhaust flame arrester, determine the effectiveness of the low water sensor which will automatically activate the safety shutdown system and stop the engine at or above the minimum allowable low water level established from results of the explosion tests in § 7.100 with the engine operating at a high idle speed condition. Temporarily disable the reserve water supply, if applicable, and any safety shutdown system control that might interfere with the evaluation of the operation of the low water sensor. Prior to testing, set the water level in the wet exhaust conditioner to a level just above the minimum allowable low water level. Run the engine until the low water sensor activates the safety shutdown system and stops the engine. Measure the low water level. Attempt to restart the engine.


(6) Determine the effectiveness of the device in the intake system which is designed to shut off the air supply and stop the engine for emergency purposes with the engine operating at both a high idle speed condition and a low idle speed condition. Run the engine and activate the emergency intake air shutoff device.


(7) Determine the total air inlet restriction of the complete intake system, including the air cleaner, as measured between the intake flame arrester and the engine head with the engine operating at maximum air flow.


(8) Determine the total exhaust backpressure with the engine operating at rated horsepower as specified in § 7.103(a)(7). If a wet exhaust conditioner is used, it must be filled to the high or normal operating water level during this test.


(9) The starting mechanism shall be tested to ensure that engagement is not possible while the engine is running. Operate the engine and attempt to engage the starting mechanism.


(10) Where the lack of engine oil pressure must be overridden in order to start the engine, test the override to ensure that it does not override any of the safety shutdown sensors specified in § 7.98(i). After each safety shutdown sensor test specified in paragraphs (a)(2) through (a)(5) of this section, immediately override the engine oil pressure and attempt to restart the engine.


(b) Acceptable performance. Tests of the safety system controls shall result in the following:


(1) The coolant system temperature shutdown sensor shall automatically activate the safety shutdown system and stop the engine before the water temperature in the cooling jackets exceeds manufacturer’s specifications or 212 °F (100 °C), whichever is lower.


(2) The temperature sensor in the exhaust gas stream of a system using a dry exhaust conditioner shall automatically activate the safety shutdown system and stop the engine before the cooled exhaust gas exceeds 302 °F (150 °C).


(3) The temperature sensor in the exhaust gas stream of a system using a wet exhaust conditioner shall automatically activate the safety shutdown system and stop the engine before the cooled exhaust gas exceeds 185 °F (85 °C).


(4) The low water sensor for systems using a wet exhaust conditioner shall automatically activate the safety shutdown system and stop the engine at or above the minimum allowable low water level and prevent restarting of the engine.


(5) The emergency intake air shutoff device shall operate immediately when activated and stop the engine within 15 seconds.


(6) The total intake air inlet restriction and the total exhaust backpressure shall not exceed the engine manufacturer’s specifications.


(7) It shall not be possible to engage the starting mechanism while the engine is running, unless the starting mechanism is constructed of nonsparking material.


(8) The engine oil pressure override shall not override any of the shutdown sensors.


§ 7.104 Internal static pressure test.

(a) Test procedures. (1) Isolate and seal each segment of the intake system or exhaust system to allow pressurization.


(2) Internally pressurize each segment of the intake system or exhaust system to four times the maximum pressure observed in each segment during the tests of § 7.100, or 150 psig ±5 psig, whichever is less. Maintain the pressure for a minimum of 10 seconds.


(3) Following the pressure hold, the pressure shall be removed and the pressurizing agent removed from the intake system or exhaust system.


(b) Acceptable performance. (1) The intake system or exhaust system, during pressurization, shall not exhibit –


(i) Leakage through welds and gasketed joints; or


(ii) Leakage other than along joints meeting the explosion-proof requirements of § 7.98(q).


(2) Following removal of the pressurizing agent, the intake system or exhaust system shall not exhibit any –


(i) Changes in fastening torque;


(ii) Visible cracks in welds;


(iii) Permanent deformation affecting the length or gap of any flame-arresting paths;


(iv) Stretched or bent fastenings;


(v) Damaged threads of parts affecting the explosion-proof integrity of the intake system or exhaust system; or


(vi) Permanent distortion of any planar surface of the diesel power package exceeding 0.04-inches/linear foot.


§ 7.105 Approval marking.

Each approved diesel power package shall be identified by a legible and permanent approval plate inscribed with the assigned MSHA approval number and securely attached to the diesel power package in a manner that does not impair any explosion-proof characteristics. The grade limitation of a wet exhaust conditioner used as an exhaust flame arrester shall be included on the approval marking.


§ 7.106 Post-approval product audit.

Upon request by MSHA, but not more than once a year except for cause, the approval-holder shall make an approved diesel power package available for audit at no cost to MSHA.


§ 7.107 New technology.

MSHA may approve a diesel power package that incorporates technology for which the requirements of this subpart are not applicable if MSHA determines that the diesel power package is as safe as those which meet the requirements of this subpart.


§ 7.108 Power package checklist.

Each diesel power package bearing an MSHA approval plate shall be accompanied by a power package checklist. The power package checklist shall consist of a list of specific features that must be checked and tests that must be performed to determine if a previously approved diesel power package is in approved condition. Test procedures shall be specified in sufficient detail to allow evaluation to be made without reference to other documents. Illustrations shall be used to fully identify the approved configuration of the diesel power package.


Subpart J – Electric Motor Assemblies


Source:57 FR 61193, Dec. 23, 1992, unless otherwise noted.

§ 7.301 Purpose and effective date.

This subpart establishes the specific requirements for MSHA approval of certain explosion-proof electric motor assemblies intended for use in approved equipment in underground mines. Applications for approval or extensions of approval submitted after February 22, 1996 shall meet the requirements of this part. Those motors that incorporate features not specifically addressed in this subpart will continue to be evaluated under part 18 of this chapter.


§ 7.302 Definitions.

The following definitions apply in this subpart:


Afterburning. The combustion of any flammable mixture that is drawn into an enclosure after an internal explosion in the enclosure. This condition is determined through detection of secondary pressure peaks occurring subsequent to the initial explosion.


Cylindrical joint. A joint comprised of two contiguous, concentric, cylindrical surfaces.


Explosion-proof enclosure. A metallic enclosure used as a winding compartment, conduit box, or a combination of both that complies with the applicable requirements of § 7.304 of this part and is constructed so that it will withstand the explosion tests of § 7.306 of this part.


Fastening. A bolt, screw, or stud used to secure adjoining parts to prevent the escape of flame from an explosion-proof enclosure.


Flame-arresting path. Two or more adjoining or adjacent surfaces between which the escape of flame is prevented.


Internal free volume (of an empty enclosure). The volume remaining after deducting the volume of any part that is essential in maintaining the explosion-proof integrity of the enclosure or necessary for operation of the motor. Essential parts include the parts that constitute the flame-arresting path and those necessary to secure parts that constitute a flame-arresting path.


Motor assembly. The winding compartment including a conduit box when specified. A motor assembly is comprised of one or more explosion-proof enclosures.


Plane joint. A joint comprised of two adjoining surfaces in parallel planes.


Step (rabbet) joint. A joint comprised of two adjoining surfaces with a change or changes in direction between its inner and outer edges. A step joint may be composed of a cylindrical portion and a plane portion or of two or more plane portions.


Stuffing box. An entrance with a recess filled with packing material for cables extending through a wall of an explosion-proof enclosure.


Threaded joint. A joint consisting of a male- and a female-threaded member, both of which are the same type and gauge.


§ 7.303 Application requirements.

(a) An application for approval of a motor assembly shall include a composite drawing or drawings with the following information:


(1) Model (type), frame size, and rating of the motor assembly.


(2) Overall dimensions of the motor assembly, including conduit box if applicable, and internal free volume.


(3) Material and quantity for each of the component parts that form the explosion-proof enclosure or enclosures.


(4) All dimensions (including tolerances) and specifications required to ascertain compliance with the requirements of § 7.304 of this part.


(b) All drawings shall be titled, dated, numbered, and include the latest revision.


§ 7.304 Technical requirements.

(a) Voltage rating of the motor shall not exceed 4160 volts.


(b) The temperature of the external surfaces of the motor assembly shall not exceed 150 °C (302 °F) when operated at the manufacturers’ specified ratings.


(c) Minimum clearances between uninsulated electrical conductor surfaces, or between uninsulated conductor surfaces and grounded metal surfaces, within the enclosure shall meet the requirements of table J-1 of this section.


Table J-1 – Minimum Clearances Between Uninsulated Surfaces

Phase-to-phase voltage (rms)
Clearances (inches)
Phase-to-phase
Phase-to-ground or control circuit
0 to 2500.250.25
251 to 6000.280.25
601 to 10000.610.25
1001 to 24001.40.6
2401 to 41603.01.4

(d) Parts whose dimensions can change with the motor operation, such as ball and roller bearings and oil seals, shall not be used as flame-arresting paths.


(e) The widths of any grooves, such as grooves for holding oil seals or o-rings, shall be deducted in measuring the widths of flame-arresting paths.


(f) An outer bearing cap shall not be considered as forming any part of a flame-arresting path unless the cap is used as a bearing cartridge.


(g) Requirements for explosion-proof enclosures of motor assemblies.


(1) Enclosures shall be –


(i) Constructed of metal;


(ii) Designed to withstand a minimum internal pressure of 150 pounds per square inch (gauge);


(iii) Free from blowholes when cast; and


(iv) Explosion proof as determined by the tests set out in § 7.306 of this part.


(2) Welded joints forming an enclosure shall be –


(i) Continuous and gas-tight; and


(ii) Made in accordance with or exceed the American Welding Society Standard AWS D14.4-77, “Classification and Application of Welded Joints for Machinery and Equipment,” or meet the test requirements set out in § 7.307 of this part. AWS D14.4-77 is incorporated by reference and has been approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from the American Welding Society, Inc., 2501 NW 7th Street, Miami, FL 33125. Copies may be inspected at the U.S. Department of Labor, Mine Safety and Health Administration, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.


(3) External rotating parts shall not be constructed of aluminum alloys containing more than 0.6 percent magnesium. Non-metallic rotating parts shall be provided with a means to prevent an accumulation of static electricity.


(4) Threaded covers and mating parts shall be designed with Class 1A and 1B (coarse, loose fitting) threads. The covers shall be secured against loosening.


(5) Flat surfaces between fastening holes that form any part of a flame-arresting path shall be plane to within a maximum deviation of one-half the maximum clearance specified in paragraph (g)(19) of this section. All surfaces forming a flame-arresting path shall be finished during the manufacturing process to not more than 250 microinches. A thin film of nonhardening preparation to inhibit rusting may be applied to these finished metal surfaces as long as the final surface can be readily wiped free of any foreign materials.


(6) For a laminated stator frame, it shall be impossible to insert a 0.0015 inch thickness gauge to a depth exceeding
1/8 inch between adjacent laminations or between end rings and laminations.


(7) Lockwashers, or equivalent, shall be provided for all fastenings. Devices other than lockwashers shall meet the requirements of § 7.308 of this part. Equivalent devices shall only be used in the configuration in which they were tested.


(8) Fastenings shall be as uniform in size as practicable to preclude improper installation.


(9) Holes for fastenings in an explosion-proof enclosure shall be threaded to ensure that all specified bolts or screws will not bottom even if the washers are omitted.


(10) Holes for fastenings shall not penetrate to the interior of an explosion-proof enclosure, except holes made through motor casings for bolts, studs, or screws to hold essential parts, such as pole pieces, brush rigging, and bearing cartridges. The attachments of such parts shall be secured against loosening. The threaded holes in these parts shall be blind unless the fastenings are inserted from the inside, in which case the fastenings shall not be accessible with the rotor in place.


(11) For direct current motor assemblies with narrow interpoles, the distance from the edge of the pole piece to any bolt hole in the frame shall be at least
1/8 inch. If the distance is
1/8 to
1/4 inch, the diametrical clearance for the pole bolt shall not exceed
1/64 inch for not less than
1/2 inch through the frame. Furthermore, the pole piece shall have the same radius as the inner surface of the frame. Pole pieces may be shimmed as necessary. If used, the total resulting thickness of the shims shall be specified. The shim assembly shall meet the same requirements as the pole piece.


(12) Coil-thread inserts, if used in holes for fastenings, shall meet the following:


(i) The inserts shall have internal screw threads.


(ii) The holes for the inserts shall be drilled and tapped consistent with the insert manufacturer’s specifications.


(iii) The inserts shall be installed consistent with the insert manufacturer’s specifications.


(iv) The insert shall be of sufficient length to ensure the minimum thread engagement of fastening specified in paragraph (g)(19) of this section.


(13) A minimum of
1/8 inch of stock shall be left at the center of the bottom of each blind hole that could penetrate into the interior of an explosion-proof enclosure.


(14) Fastenings shall be used only for attaching parts that are essential in maintaining the explosion-proof integrity of the enclosure, or necessary for the operation of the motor. They shall not be used for making electrical connections.


(15) Through holes not in use shall be closed with a metal plug. Plugs, including eyebolts, in through holes where future access is desired shall meet the flame-arresting paths, lengths, and clearances of paragraph (g)(19) of this section and be secured by spot welding or brazing. The spot weld or braze may be on a plug, clamp, or fastening (for example see figure J-1). Plugs for holes where future access is not desired shall be secured all around by a continuous gas-tight weld.


(16) O-rings, if used in a flame-arresting path, shall meet the following:


(i) When the flame-arresting path is in one plane, the o-ring shall be located at least one-half the acceptable flame-arresting path length specified in paragraph (g)(19) of this section from within the outside edge of the path (see figure J-2).


(ii) When the flame-arresting path is one of the plane-cylindrical type (step joint), the o-ring shall be located at least
1/2 inch from within the outer edge of the plane portion (see figure J-3), or at the junction of the plane and cylindrical portion of the joint (see figure J-4), or in the cylindrical portion (see figure J-5).


(17) Mating parts comprising a pressed fit shall result in a minimum interference of 0.001 inch between the parts. The minimum length of the pressed fit shall be equal to the minimum thickness requirement of paragraph (g)(19) of this section for the material in which the fit is made.


(18) The flame-arresting path of threaded joints shall conform to the requirements of paragraph (g)(19) of this section.


(19) Explosion-proof enclosures shall meet the requirements set out in table J-2 of this section, based on the internal free volume of the empty enclosure.


Table J-2 – Explosion-Proof Requirements Based on Volume


Volume of empty enclosure
Less than 45 cu. ins.
45 to 124 cu. ins. inclusive
More than 124 cu. ins.
Minimum thickness of material for walls
1

1/8

3/16

1/4
Minimum thickness of material for flanges and covers
2
1/4

3
3/8

3
1/2
Minimum width of joint; all in one plane
1/2

3/4
1″
Maximum clearance; joint all in one plane0.002″0.003″0.004″
Minimum width of joint, portions of which are in different planes; cylinders or equivalent
4
3/8

4
5/8

4
3/4
Maximum clearances; joint in two or more planes, cylinders or equivalent:
5
(a) Portion perpendicular to plane
6
0.008″0.008″0.008″
(b) Plane portion0.006″0.006″0.006″
Maximum fastening
7 8 spacing; joints all in one plane
(
16)
(
16)
(
16)
Maximum fastening spacing; joints, portions of which are in different planes(
17)
(
17)
(
17)
Minimum diameter of fastening
9 (without regard to type of joint)

1/4

1/4

3/8
Minimum thread engagement of fastening
10

1/4

1/4

3/8
Maximum diametrical clearance between fastening body and unthreaded holes through which it passes
8 11 12

1/64

1/32

1/16
Minimum distance from interior of enclosure to the edge of a fastening hole:
8 13
Joint – minimum width 1″
14
7/16
Joint – less than 1″ wide
1/8

3/16
Cylindrical Joints
Shaft centered by ball or roller bearings:
Minimum length of flame-arresting path
1/2

3/4
1″
Maximum diametrical clearance0.020″0.025″0.030″
Other cylindrical joints:
15
Minimum length of flame-arresting path
1/2

3/4
1″
Maximum diametrical clearance0.006″0.008″0.010″


1 This is the minimal nominal dimension when applied to standard steel plate.


2
1/32 inch less is allowable for machining rolled plate.


3
1/16 inch less is allowable for machining rolled plate.


4 If only two planes are involved, neither portion of a joint shall be less than
1/8 inch wide, unless the wider portion conforms to the same requirements as those for a joint that is all in one plane. If more than two planes are involved (as in labyrinths or tongue-and-groove joints) the combined lengths of those portions having prescribed clearances are considered.


5 For winding compartments having internal free volume not exceeding 350 cubic inches and joints not exceeding 32 inches in outer circumference and provided with step joints between the stator frame and the end bracket the following dimensions shall apply:


Dimensions of Rabbet (Step) Joints-Inches

[See figure J-6 in appendix]

Minimum total width
Minimum width of clamped radial portion
Maximum clearance of radial portion
Maximum diametrical clearance at axial portion

3/8

3/64
0.00150.003

1/2

3/64
0.0020.003

1/2

3/32
0.0020.004


6 The allowable diametrical clearance is 0.008 inch when the portion perpendicular to the plane portion is
1/4 inch or greater in length. If the perpendicular portion is more than
1/8 inch but less than
1/4 inch wide, the diametrical clearance shall not exceed 0.006 inch.


7 Studs, when provided, shall bottom in blind holes, be completely welded in place, or have the bottom of the hole closed with a plug secured by weld or braze. Fastenings shall be provided at all corners.


8 The requirements as to diametrical clearance around the fastening and minimum distance from the fastening hole to the inside of the explosion-proof enclosure apply to steel dowel pins. In addition, when such pins are used, the spacing between centers of the fastenings on either side of the pin shall not exceed 5 inches.


9 Fastening diameters smaller than specified may be used if the enclosure meets the test requirements of 30 CFR 7.307 and then 7.306 in that order.


10 Minimum thread engagement shall be equal to or greater than the diameter of the fastening specified, or the enclosure must meet the test requirements of 30 CFR 7.307 and then 7.306 in that order.


11 This maximum clearance applies only when the fastening is located within the flame-arresting path.


12 Threaded holes for fastening bolts shall be machined to remove burrs or projections that affect planarity of a surface forming a flame-arresting path.


13 Edge of the fastening hole shall include the edge of any machining done to the fastening hole, such as chamfering.


14 If the diametrical clearance for fastenings does not exceed
1/32 inch, then the minimum distance shall be
1/4 inch.


15 Shafts or operating rods through journal bearings shall be at least
1/4″ in diameter. The length of the flame-arresting path shall not be reduced when a pushbutton is depressed. Operating rods shall have a shoulder or head on the portion inside the enclosure. Essential parts riveted or bolted to the inside portion are acceptable in lieu of a head or shoulder, but cotter pins and similar devices shall not be used.


16 6″ with a minimum of 4 fastenings.


17 8″ with a minimum of 4 fastenings.


(h) Lead entrances. (1) Each cable, which extends through an outside wall of the motor assembly, shall pass through a stuffing-box lead entrance (see figure J-7). All sharp edges shall be removed from stuffing boxes, packing nuts, and other lead entrance (gland) parts, so that the cable jacket is not damaged.


(2) When the packing is properly compressed, the gland nut shall have –


(i) A clearance distance of
1/8 inch or more, with no maximum, to travel without interference by parts other than packing; and


(ii) A minimum of three effective threads engaged (see figures J-8, J-9, and J-10).


(3) Packing nuts (see figure J-7) and stuffing boxes shall be secured against loosening (see figure J-11).


(4) Compressed packing material shall be in contact with the cable jacket for a length of not less than
1/2 inch.


(5) Requirements for lead entrances in which MSHA accepted rope packing material is specified, are:


(i) Rope packing material shall be acceptable under § 18.37(e) of this chapter.


(ii) The width of the space for packing material shall not exceed by more than 50 percent the diameter or width of the uncompressed packing material (see figure J-12).


(iii) The maximum diametrical clearance, using the specified tolerances, between the cable and the through holes in the gland parts adjacent to the packing (stuffing box, packing nut, hose tube, or bushings) shall not exceed 75 percent of the nominal diameter or width of the packing material (see figure J-13).


(6) Requirements for lead entrances in which grommet packing made of compressible material is specified, are:


(i) The grommet packing material shall be accepted by MSHA as flame-resistant material under § 18.37(f)(1) of this chapter.


(ii) The diametrical clearance between the cable jacket and the nominal inside diameter of the grommet shall not exceed
1/16 inch, based on the nominal specified diameter of the cable (see figure J-14).


(iii) The diametrical clearance between the nominal outside diameter of the grommet and the inside wall of the stuffing box shall not exceed
1/16 inch (see figure J-14).


(i) Combustible gases from insulating material. (1) Insulating materials that give off flammable or explosive gases when decomposed electrically shall not be used within explosion-proof enclosures where the materials are subjected to destructive electrical action.


(2) Parts coated or impregnated with insulating materials shall be treated to remove any combustible solvent before assembly in an explosion-proof enclosure.


[57 FR 61193, Dec. 23, 1992, as amended at 73 FR 52210, Sept. 9, 2008]


§ 7.305 Critical characteristics.

The following critical characteristics shall be inspected on each motor assembly to which an approval marking is affixed:


(a) Finish, width, and planarity of surfaces that form any part of a flame-arresting path.


(b) Clearances between mating parts that form flame-arresting paths.


(c) Thickness of walls, flanges, and covers that are essential in maintaining the explosion-proof integrity of the enclosure.


(d) Spacing of fastenings.


(e) Length of thread engagement on fastenings and threaded parts that assure the explosion-proof integrity of the enclosure.


(f) Use of lockwasher or equivalent with all fastenings.


(g) Dimensions which affect compliance with the requirements for packing gland parts in § 7.304 of this part.


§ 7.306 Explosion tests.

(a) The following shall be used for conducting an explosion test:


(1) An explosion test chamber designed and constructed to contain an explosive gas mixture to surround and fill the motor assembly being tested. The chamber must be sufficiently darkened and provide viewing capabilities of the flame-arresting paths to allow observation during testing of any discharge of flame or ignition of the explosive mixture surrounding the motor assembly.


(2) A methane gas supply with at least 98 by volume per centum of combustible hydrocarbons, with the remainder being inert. At least 80 percent by volume of the gas shall be methane.


(3) Coal dust having a minimum of 22 percent dry volatile matter and a minimum heat constant of 11,000 moist BTU (coal containing natural bed moisture but not visible surface water) ground to a fineness of minus 200 mesh U.S. Standard sieve series.


(4) An electric spark ignition source with a minimum of 100 millijoules of energy.


(5) A pressure recording system that will indicate the pressure peaks resulting from the ignition and combustion of explosive gas mixtures within the enclosure being tested.


(b) General test procedures. (1) Motor assemblies being tested shall –


(i) Be equipped with unshielded bearings regardless of the type of bearings specified; and


(ii) Have all parts that do not contribute to the operation or assure the explosion-proof integrity of the enclosure, such as oil seals, grease fittings, hose conduit, cable clamps, and outer bearing caps (which do not house the bearings) removed from the motor assembly.


(2) Each motor assembly shall be placed in the explosion test chamber and tested as follows:


(i) The motor assembly shall be filled with and surrounded by an explosive mixture of the natural gas supply and air. The chamber gas concentrations shall be between 6.0 by volume per centum and the motor assembly natural gas concentration just before ignition of each test. Each externally visible flame-arresting path fit shall be observed for discharge of flames for at least two of the tests, including one with coal dust added.


(ii) A single spark source is used for all testing. Pressure shall be measured at each end of the winding compartment simultaneously during all tests. Quantity and location of test holes shall permit ignition on each end of the winding compartment and recording of pressure on the same and opposite ends as the ignition.


(iii) Motor assemblies incorporating a conduit box shall have the pressure in the conduit box recorded simultaneously with the other measured pressures during all tests. Quantity and location of test holes in the conduit box shall permit ignition and recording of pressure as required in paragraphs (c)(1) and (c)(4)(i) of this section.


(iv) The motor assembly shall be completely purged and recharged with a fresh explosive gas mixture from the chamber or by injection after each test. The chamber shall be completely purged and recharged with a fresh explosive gas mixture as necessary. The oxygen level of the chamber gas mixture shall be no less than 18 percent by volume for testing. In the absence of oxygen monitoring equipment, the maximum number of tests conducted before purging shall be less than or equal to the chamber volume divided by forty times the volume occupied by the motor assembly.


(c) Test procedures. (1) Eight tests at 9.4 ±0.4 percent methane by volume within the winding compartment shall be conducted, with the rotor stationary during four tests and rotating at rated speed (rpm) during four tests. The ignition shall be at one end of the winding compartment for two stationary and two rotating tests, and then switched to the opposite end for the remaining four tests. If a nonisolated conduit box is used, then two additional tests, one stationary and one rotating, shall be conducted with ignition in the conduit box at a point furthest away from the opening between the conduit box and the winding compartment.


(2) Four tests at 7.0 ±0.3 percent methane by volume within the winding compartment shall be conducted with the rotor stationary, 2 ignitions at each end.


(3) Four tests at 9.4 ±0.4 percent methane by volume plus coal dust shall be conducted. A quantity of coal dust equal to 0.05 ounces per cubic foot of internal free volume of the winding compartment plus the nonisolated conduit box shall be introduced into each end of the winding compartment and nonisolated conduit box to coat the interior surface before conducting the first of the four tests. The coal dust introduced into the conduit box shall be proportional to its volume. The remaining coal dust shall be equally divided between the winding compartment ends. For two tests, one stationary and one rotating, the ignition shall be either in the conduit box or one end of the connected winding compartment, whichever produced the highest pressure in the previous tests. The two remaining tests, one stationary and one rotating, shall be conducted with the ignition in the winding compartment end furthest away from the conduit box.


(4) For motor assemblies incorporating a conduit box which is isolated from the winding compartment by an isolating barrier the following additional tests shall be conducted –


(i) For conduit boxes with an internal free volume greater than 150 cubic inches, two ignition points shall be used, one as close to the geometric center of the conduit box as practical and the other at the furthest point away from the isolating barrier between the conduit box and the winding compartment. Recording of pressure shall be on the same and opposite sides as the ignition point furthest from the isolating barrier between the conduit box and the winding compartment. Conduit boxes with an internal free volume of 150 cubic inches or less shall have one test hole for ignition located as close to the geometric center of the conduit box as practical and one for recording of pressure located on a side of the conduit box.


(ii) The conduit box shall be tested separately. Six tests at 9.4 ±0.4 percent methane by volume within the conduit box shall be conducted followed by two tests at 7.0 ±0.3 percent methane by volume. Then two tests at 9.4 ±0.4 percent methane by volume with a quantity of coal dust equal to 0.05 ounces per cubic foot of internal free volume of the conduit box and meeting the specifications in paragraph (c)(3) of this section shall be conducted. For conduit boxes with an internal free volume of more than 150 cubic inches, the number of tests shall be evenly divided between each ignition point.


(iii) The motor assembly shall be tested following removal of the isolating barrier or one sectionalizing terminal (as applicable). Six tests at 9.4 ±0.4 percent methane by volume in the winding compartment and conduit box shall be conducted using three ignition locations. The ignition shall be at one end of the winding compartment for one stationary and one rotating test; the opposite end for one stationary and one rotating test; and at the ignition point that produced the highest pressure on the previous test in paragraph (c)(4)(ii) of this section in the conduit box for one stationary and one rotating test. Motor assemblies that use multiple sectionalizing terminals shall have one test conducted as each additional terminal is removed. Each of these tests shall use the rotor state and ignition location that produced the highest pressure in the previous tests.


(d) A motor assembly incorporating a conduit box that is isolated from the winding compartment that exhibits pressures exceeding 110 psig, while testing during removal of any or all isolating barriers as specified in paragraph (c)(4) of this section, shall have a warning statement on the approval plate. This statement shall warn that the isolating barrier must be maintained to ensure the explosion-proof integrity of the motor assembly. A statement is not required when the motor assembly has withstood a static pressure of twice the maximum pressure recorded in the explosion tests of paragraph (c)(4) of this section. The static pressure test shall be conducted on the motor assembly with all isolating barriers removed, and in accordance with § 7.307 of this part.


(e) Acceptable performance. Explosion tests of a motor assembly shall not result in –


(1) Discharge of flames.


(2) Ignition of the explosive mixture surrounding the motor assembly in the chamber.


(3) Development of afterburning.


(4) Rupture of any part of the motor assembly or any panel or divider within the motor assembly.


(5) Clearances, in excess of those specified in this subpart, along accessible flame-arresting paths, following any necessary retightening of fastenings.


(6) Pressure exceeding 110 psig, except as provided in paragraph (d) of this section unless the motor assembly has withstood a static pressure of twice the maximum pressure recorded in the explosion tests of this section following the static pressure test procedures of § 7.307 of this part.


(7) Permanent deformation greater than 0.040 inches per linear foot.


§ 7.307 Static pressure test.

(a) Test procedure. (1) The enclosure shall be internally pressurized to a minimum of 150 psig and the pressure maintained for a minimum of 10 seconds.


(2) Following the pressure hold, the pressure shall be removed and the pressurizing agent removed from the enclosure.


(b) Acceptable performance. (1) The enclosure during pressurization shall not exhibit –


(i) Leakage through welds or casting; or


(ii) Rupture of any part that affects the explosion-proof integrity of the enclosure.


(2) The enclosure following removal of the pressurizing agent shall not exhibit –


(i) Visible cracks in welds;


(ii) Permanent deformation exceeding 0.040 inches per linear foot; or


(iii) Clearances, in excess of those specified in this subpart, along accessible flame-arresting paths, following any necessary retightening of fastenings.


§ 7.308 Lockwasher equivalency test.

(a) Test procedure. (1) Each test sample shall be an assembly consisting of a fastening with a locking device. Each standard sample shall be an assembly consisting of a fastening with a lockwasher.


(2) Five standard samples and five test samples shall be tested.


(3) Each standard and test sample shall use a new fastening of the same specifications as being used on the motor assembly.


(4) A new tapped hole shall be used for each standard and test sample. The hole shall be of the same specifications as used on the motor assembly.


(5) Each standard and test sample shall be inserted in the tapped hole and continuously and uniformly tightened at a speed not to exceed 30 rpm until the fastening’s proof load is achieved. The torquing device shall not contact the locking device or the threaded portion of the fastening.


(6) Each standard and test sample shall be engaged and disengaged for 15 full cycles.


(b) Acceptable performance. The minimum torque value required to start removal of the fastening from the installed position (minimum breakway torque) for any cycle of any test sample shall be greater than or equal to the average breakway torque of each removal cycle of every standard sample.


§ 7.309 Approval marking.

Each approved motor assembly shall be identified by a legible and permanent approval plate inscribed with the assigned MSHA approval number and a warning statement as specified in § 7.306(d) of this part. The plate shall be securely attached to the motor assembly in a manner that does not impair any explosion-proof characteristics.


§ 7.310 Post-approval product audit.

Upon request by MSHA but not more than once a year, except for cause, the approval holder shall make a motor assembly available for audit at no cost.


§ 7.311 Approval checklist.

Each motor assembly bearing an MSHA approval marking shall be accompanied by a list of items necessary for maintenance of the motor assembly as approved.


Appendix I to Subpart J of Part 7











Subpart K – Electric Cables, Signaling Cables, and Cable Splice Kits


Source:57 FR 61220, Dec. 23, 1992, unless otherwise noted.

§ 7.401 Purpose and effective date.

This subpart establishes the flame-resistant requirements for approval of electric cables, signaling cables and cable splice kit designs. Applications for approval or extension of approval submitted after February 22, 1994 shall meet the requirements of this subpart.


§ 7.402 Definitions.

The following definitions apply in this subpart.


Component. Any material in a cable splice kit which becomes part of a splice.


Conductor. A bare or insulated wire or combination of wires not insulated from one another, suitable for carrying an electric current.


Electric Cable. An assembly of one or more insulated conductors of electric current under a common or integral jacket. A cable may also contain one or more uninsulated conductors.


Jacket. A nonmetallic abrasion-resistant outer covering of a cable or splice.


Power Conductor. An insulated conductor of a cable assembly through which the primary electric current or power is transmitted.


Signaling Cable. A fiber optic cable, or a cable containing electric conductors of a cross-sectional area less than #14 AWG used where the circuit cannot deliver currents which would increase conductor temperatures beyond that established for the current-carrying capacity of the conductors.


Splice. The mechanical joining of one or more severed conductors in a single length of a cable including the replacement of insulation and jacket.


Splice Kit. A group of materials and related instructions which clearly identify all components and detail procedures used in safely making a flame-resistant splice in an electric cable.


§ 7.403 Application requirements.

(a) Electric cables and signaling cables. A single application may address two or more sizes, types, and constructions if the products do not differ in composition of materials or basic design. Applications shall include the following information for each product:


(1) Product information:


(i) Cable type (for example, G or G-GC).


(ii) Construction (for example, round or flat).


(iii) Number and size (gauge) of each conductor.


(iv) Voltage rating for all cables containing electric conductors.


(v) For electric cables, current-carrying capacity of each conductor, with corresponding ambient temperature upon which the current rating (ampacity) is based, of each power conductor.


(2) Design standard. Specify any published consensus standard used and fully describe any deviations from it, or fully describe any nonstandard design used.


(3) Materials. Type and identifying numbers for each material comprising the finished assembly.


(b) Splice kit. A single application may address two or more sizes, types, and constructions if the products do not differ in composition of materials or basic design. Applications shall include the following information for each product:


(1) Product information:


(i) Trade name or designation (for example, style or code number).


(ii) Type or kit (for example, shielded or nonshielded).


(iii) Voltage rating.


(2) Design standard. Specify any published design standard used and fully describe any deviations from it, or provide complete final assembly dimensions for all components for each cable that the splice kit is designed to repair.


(3) Materials. Type of materials, supplier, supplier’s stock number or designation for each component.


(4) Complete splice assembly instructions which clearly identify all components and detail procedures used in making the splice.


§ 7.404 Technical requirements.

(a) Electric cables and splices shall be flame resistant when tested in accordance with § 7.407.


(b) Signaling cables shall be flame resistant when tested in accordance with § 7.408.


§ 7.405 Critical characteristics.

(a) A sample from each production run, batch, or lot of manufactured electric cable, signaling cable, or splice made from a splice kit shall be flame tested, or


(b) A sample of the materials that contribute to the flame-resistant characteristic of the cable or splice and a sample of the cable or splice kit assembly shall be visually inspected or tested through other means for each production run, batch, or lot to ensure that the finished product meets the flame-resistance test.


§ 7.406 Flame test apparatus.

The principal parts of the apparatus used to test for flame resistance of electric cables, signaling cables and splices shall include#:


(a) Test chamber. A rectangular enclosure measuring 17 inches deep by 14
1/2 inches high by 39 inches wide and completely open at the top and front. The floor or base of the chamber shall be fabricated or lined with a noncombustible material that will not extinguish burning matter which may fall from the test specimen during testing. The chamber shall have permanent connections mounted to the back wall, sides, or floor of the chamber which extend to the sample end location. These are used to energize the electric cable and splice specimens. They are not used, but may stay in place, when testing signaling cables.


(b) Specimen holder (support). A specimen holder (support) consisting of three separate metal rods each measuring approximately
3/16 inch in diameter (nominal) to support the specimen. The horizontal portion of the rod which contacts the test specimen shall be approximately 12 inches in length.


(c) Gas ignition source. A standard natural gas type Tirrill burner, with a nominal inside diameter of
3/8 inch, to apply the flame to the test specimen. The fuel for the burner shall be natural gas composed of at least 96 percent combustible hydrocarbons, with at least 80 percent being methane.


(d) Current source. (For electric cables and splices only). A source of electric current (either alternating current or direct current) for heating the power conductors of the test specimen. The current source shall have a means to regulate current flow through the test specimen and have an open circuit voltage not exceeding the voltage rating of the test specimen.


(e) Current measuring device. (For electric cables and splices only). An instrument to monitor the effective value of heating current flow through the power conductors of the specimen within an accuracy of ±1 percent.


(f) Temperature measuring device. (For electric cables and splices only). An instrument to measure conductor temperature within an accuracy of ±2 percent without the necessity of removing material from the test specimen in order to measure the temperature.


§ 7.407 Test for flame resistance of electric cables and cable splices.

(a) Test procedure. (1) For electric cables, prepare 3 specimens of cable, each 3 feet in length, by removing 5 inches of jacket material and 2
1/2 inches of conductor insulation from both ends of each test specimen. For splices, prepare a splice specimen in each of 3 sections of MSHA-approved flame-resistant cable. The cable shall be of the type that the splice kit is designed to repair. The finished splice shall not exceed 18 inches or be less than 6 inches in length for test purposes. The spliced cables shall be 3 feet in length with the midpoint of the splice located 14 inches from one end. Both ends of each of the spliced cables shall be prepared by removing 5 inches of jacket material and 2
1/2 inches of conductor insulation. The type, amperage, voltage rating, and construction of the cable shall be compatible with the splice kit design. Each splice shall be made in accordance with the instructions provided with the splice kit.


(2) Prior to testing, condition each test specimen for a minimum of 24 hours at a temperature of 70 ±10 °F (21.1 ±5.5 °C) and a relative humidity of 55 ±10 percent. These environmental conditions shall be maintained during testing.


(3) For electric cables, locate the sensing element of the temperature measuring device 26 inches from one end of each test specimen. For splices, locate the sensing element 12 inches from the midpoint of the splice and 10 inches from the end of the cable. The sensing element must be secured so that it remains in direct contact with the metallic portion of the power conductor for the duration of the flame-resistant test. If a thermocouple-type temperature measuring instrument is used, connect the sensing element through the cable jacket and power conductor insulation. Other means for monitoring conductor temperature may be used, provided the temperature measurement is made at the same location. If the jacket and conductor insulation must be disturbed to insert the temperature measuring device, each must be restored as closely as possible to its original location and maintained there for the duration of the testing.


(4) Center the test specimen horizontally in the test chamber on the three rods. The three rods shall be positioned perpendicular to the longitudinal axis of the test specimen and at the same height, which permits the tip of the inner cone from the flame of the gas burner, when adjusted in accordance with the test procedure, to touch the jacket of the test specimen. The specimen shall be maintained at this level for the duration of the flame test. The two outermost rods shall be placed so that 1 inch of cable jacket extends beyond each rod. For electric cables, the third rod shall be placed 14 inches from the end of the test specimen nearer the temperature monitoring location on the specimen. For splices, the third rod shall be placed between the splice and the temperature monitoring location at a distance 8 inches from the midpoint of the splice. The specimen shall be free from external air currents during testing.


(5) Adjust the gas burner to give an overall blue flame 5 inches high with a 3-inch inner cone. There shall be no persistence of yellow coloration.


(6) Connect all power conductors of the test specimen to the current source. The connections shall be secure and compatible with the size of the cable’s power conductors in order to reduce contact resistance.


(7) Energize all power conductors of the test specimen with an effective heating current value of 5 times the power conductor ampacity rating (to the nearest whole ampere) at an ambient temperature of 104 °F (40 °C).


(8) Monitor the electric current through the power conductors of the test specimen with the current measuring device. Adjust the amount of heating current, as required, to maintain the proper effective heating current value within ±5 percent until the power conductors reach a temperature of 400 °F (204.4 °C).


(9) For electric cables, apply the tip of the inner cone from the flame of the gas burner directly beneath the test specimen for 60 seconds at a location 14 inches from one end of the cable and between the supports separated by a 16-inch distance. For splices, apply the tip of the inner cone from the flame of a gas burner for 60 seconds beneath the midpoint of the splice jacket.


(10) After subjecting the test specimen to external flame for the specified time, fully remove the flame of the gas from beneath the specimen without disturbing air currents within the test chamber. Simultaneously turn off the heating current.


(11) Record the amount of time the test specimen continues to burn after the flame from the gas burner has been removed. The duration of burning includes the burn time of any material that falls from the test specimen after the flame from the gas has been removed.


(12) Record the length of burned (charred) area of each test specimen measured longitudinally along the cable axis.


(13) Repeat the procedure for the remaining two specimens.


(b) Acceptable performance. Each of the three test specimens shall meet the following criteria:


(1) The duration of burning shall not exceed 240 seconds.


(2) The length of the burned (charred) area shall not exceed 6 inches.


§ 7.408 Test for flame resistance of signaling cables.

(a) Test procedure. (1) Prepare 3 samples of cable each 2 feet long.


(2) Prior to testing, condition each test specimen for a minimum of 24 hours at a temperature of 70 ±10 °F (21.1 ±5.5 °C) and relative humidity of 55 ±10 percent. These environmental conditions shall be maintained during testing.


(3) Center the test specimen horizontally in the test chamber on the three rods. The three rods shall be positioned perpendicular to the longitudinal axis of the test specimen and at the same height, which permits the tip of the inner cone from the flame of the gas burner, when adjusted in accordance with the test procedure, to touch the test specimen. The specimen shall be maintained at this height for the duration of the flame test. The two outermost rods shall be placed so that 1 inch of cable extends beyond each rod. The third rod shall be placed at the midpoint of the cable. The specimen shall be free from external air currents during testing.


(4) Adjust the gas burner to give an overall blue flame 5 inches high with a 3-inch inner cone. There shall be no persistence of yellow coloration.


(5) Apply the tip of the inner cone from the flame of the gas burner for 30 seconds directly beneath the specimen centered between either and support and the center support.


(6) After subjecting the test specimen to external flame for the specified time, fully remove the flame of the gas from beneath the specimen without disturbing air currents within the test chamber.


(7) Record the amount of time the test specimen continues to burn after the flame from the gas burner has been removed. The duration of burning includes the burn time of any material that falls from the test specimen after the flame from the gas has been removed.


(8) Record the length of burned (charred) area of each test specimen measured longitudinally along the cable axis.


(9) Repeat the procedure for the remaining two specimens.


(b) Acceptable performance. Each of the three test specimens shall meet the following criteria:


(1) The duration of burning shall not exceed 60 seconds.


(2) The length of the burned (charred) area shall not exceed 6 inches.


§ 7.409 Approval marking.

Approved electric cables, signaling cables, and splices shall be legibly and permanently marked with the MSHA-assigned approval marking. For electric cables and signaling cables, the marking shall appear at intervals not exceeding 3 feet and shall include the MSHA-assigned approval number in addition to the number and size (gauge) of conductors and cable type. For cables containing electric conductors, the marking shall also include the voltage rating. For splices, the marking shall be placed on the jacket so that it will appear at least once on the assembled splice.


§ 7.410 Post-approval product audit.

Upon request by MSHA, but no more than once a year except for cause, the approval holder shall supply to MSHA for audit at no cost –


(a) 12 feet of an approved electric cable or approved signaling cable; or


(b) 3 splice kits of one approved splice kit design and 12 feet of MSHA-assigned cable that the splice kit is designed to repair.


§ 7.411 New technology.

MSHA may approve cable products or splice kits that incorporate technology for which the requirements of this subpart are not applicable if the Agency determines that they are as safe as those which meet the requirements of this subpart.


Subpart L – Refuge Alternatives


Source:74 FR 80694, Dec. 31, 2008, unless otherwise noted.

§ 7.501 Purpose and scope.

This subpart L establishes requirements for MSHA approval of refuge alternatives and components for use in underground coal mines. Refuge alternatives are intended to provide a life-sustaining environment for persons trapped underground when escape is impossible.


§ 7.502 Definitions.

The following definitions apply in this subpart:


Apparent temperature. A measure of relative discomfort due to the combined effects of air movement, heat, and humidity on the human body.


Breathable oxygen. Oxygen that is at least 99 percent pure with no harmful contaminants.


Flash fire. A fire that rapidly spreads through a diffuse fuel, such as airborne coal dust or methane, without producing damaging pressure.


Noncombustible material. Material, such as concrete or steel, that will not ignite, burn, support combustion, or release flammable vapors when subjected to fire or heat.


Overpressure. The highest pressure over the background atmospheric pressure that could result from an explosion, which includes the impact of the pressure wave on an object.


Refuge alternative. A protected, secure space with an isolated atmosphere and integrated components that create a life-sustaining environment for persons trapped in an underground coal mine.


§ 7.503 Application requirements.

(a) An application for approval of a refuge alternative or component shall include:


(1) The refuge alternative’s or component’s make and model number, if applicable.


(2) A list of the refuge alternative’s or component’s parts that includes –


(i) The MSHA approval number for electric-powered equipment;


(ii) Each component’s or part’s in-mine shelf life, service life, and recommended replacement schedule;


(iii) Materials that have a potential to ignite used in each component or part with their MSHA approval number; and


(iv) A statement that the component or part is compatible with other components and, upon replacement, is equivalent to the original component or part.


(3) The capacity and duration (the number of persons it is designed to maintain and for how long) of the refuge alternative or component on a per-person per-hour basis.


(4) The length, width, and height of the space required for storage of each component.


(b) The application for approval of the refuge alternative shall include the following:


(1) A description of the breathable air component, including drawings, air-supply sources, piping, regulators, and controls.


(2) The maximum volume, excluding the airlock; the dimensions of floor space and volume provided for each person using the refuge alternative; and the floor space and volume of the airlock.


(3) The maximum positive pressures in the interior space and the airlock and a description of the means used to limit or control the positive pressure.


(4) The maximum allowable apparent temperature of the interior space and the airlock and the means to control the apparent temperature.


(5) The maximum mine air temperature under which the refuge alternative is designed to operate when the unit is fully occupied.


(6) Drawings that show the features of each component and contain sufficient information to document compliance with the technical requirements.


(7) A manual that contains sufficient detail for each refuge alternative or component addressing in-mine transportation, operation, and maintenance of the unit.


(8) A summary of the procedures for deploying refuge alternatives.


(9) A summary of the procedures for using the refuge alternative.


(10) The results of inspections, evaluations, calculations, and tests conducted under this subpart.


(c) The application for approval of the air-monitoring component shall specify the following:


(1) The operating range, type of sensor, gas or gases measured, and environmental limitations, including the cross-sensitivity to other gases, of each detector or device in the air-monitoring component.


(2) The procedure for operation of the individual devices so that they function as necessary to test gas concentrations over a 96-hour period.


(3) The procedures for monitoring and maintaining breathable air in the airlock, before and after purging.


(4) The instructions for determining the quality of the atmosphere in the airlock and refuge alternative interior and a means to maintain breathable air in the airlock.


(d) The application for approval of the harmful gas removal component shall specify the following:


(1) The volume of breathable air available for removing harmful gas both at start-up and while persons enter through the airlock.


(2) The maximum volume of each gas that the component is designed to remove on a per-person per-hour basis.


§ 7.504 Refuge alternatives and components; general requirements.

(a) Refuge alternatives and components: (1) Electrical components that are exposed to the mine atmosphere shall be approved as intrinsically safe for use. Electrical components located inside the refuge alternative shall be either approved as intrinsically safe or approved as permissible.


(2) Shall not produce continuous noise levels in excess of 85 dBA in the structure’s interior.


(3) Shall not liberate harmful or irritating gases or particulates into the structure’s interior or airlock.


(4) Shall be designed so that the refuge alternative can be safely moved with the use of appropriate devices such as tow bars.


(5) Shall be designed to withstand forces from collision of the refuge alternative structure during transport or handling.


(b) The apparent temperature in the structure shall be controlled as follows:


(1) When used in accordance with the manufacturer’s instructions and defined limitations, the apparent temperature in the fully occupied refuge alternative shall not exceed 95 degrees Fahrenheit (°F).


(2) Tests shall be conducted to determine the maximum apparent temperature in the refuge alternative when used at maximum occupancy and in conjunction with required components. Test results including calculations shall be reported in the application.


(c) The refuge alternative shall include:


(1) A two-way communication facility that is a part of the mine communication system, which can be used from inside the refuge alternative; and accommodations for an additional communication system and other requirements as defined in the communications portion of the operator’s approved Emergency Response Plan.


(2) Lighting sufficient for persons to perform tasks.


(3) A means to contain human waste effectively and minimize objectionable odors.


(4) First aid supplies.


(5) Materials, parts, and tools for repair of components.


(6) A fire extinguisher that –


(i) Meets the requirements for portable fire extinguishers used in underground coal mines under part 75;


(ii) Is appropriate for extinguishing fires involving the chemicals used for harmful gas removal; and


(iii) Uses a low-toxicity extinguishing agent that does not produce a hazardous by-product when deployed.


(d) Containers used for storage of refuge alternative components or provisions shall be –


(1) Airtight, waterproof, and rodent-proof;


(2) Easy to open and close without the use of tools; and


(3) Conspicuously marked with an expiration date and instructions for use.


§ 7.505 Structural components.

(a) The structure shall –


(1) Provide at least 15 square feet of floor space per person and 30 to 60 cubic feet of volume per person according to the following chart. The airlock can be included in the space and volume if waste is disposed outside the refuge alternative.


Mining height

(inches)
Unrestricted volume

(cubic feet) per person *
36 or less30
>36-≤4237.5
>42-≤4845
>48-≤5452.5
>5460

* Includes an adjustment of 12 inches for clearances.


(2) Include storage space that secures and protects the components during transportation and that permits ready access to components for maintenance examinations.


(3) Include an airlock that creates a barrier and isolates the interior space from the mine atmosphere, except for a refuge alternative capable of maintaining adequate positive pressure.


(i) The airlock shall be designed for multiple uses to accommodate the structure’s maximum occupancy.


(ii) The airlock shall be configured to accommodate a stretcher without compromising its function.


(4) Be designed and made to withstand 15 pounds per square inch (psi) overpressure for 0.2 seconds prior to deployment.


(5) Be designed and made to withstand exposure to a flash fire of 300 °F for 3 seconds prior to deployment.


(6) Be made with materials that do not have a potential to ignite or are MSHA-approved.


(7) Be made from reinforced material that has sufficient durability to withstand routine handling and resist puncture and tearing during deployment and use.


(8) Be guarded or reinforced to prevent damage to the structure that would hinder deployment, entry, or use.


(9) Permit measurement of outside gas concentrations without exiting the structure or allowing entry of the outside atmosphere.


(b) Inspections or tests shall be conducted as follows:


(1) A test shall be conducted to demonstrate that trained persons can fully deploy the structure, without the use of tools, within 10 minutes of reaching the refuge alternative.


(2) A test shall be conducted to demonstrate that an overpressure of 15 psi applied to the pre-deployed refuge alternative structure for 0.2 seconds does not allow gases to pass through the structure separating the interior and exterior atmospheres.


(3) A test shall be conducted to demonstrate that a flash fire of 300 °F for 3 seconds does not allow gases to pass from the outside to the inside of the structure.


(4) An inspection shall be conducted to determine that the overpressure forces of 15 psi applied to the pre-deployed refuge alternative structure for 0.2 seconds does not prevent the stored components from operating.


(5) An inspection shall be conducted to determine that a flash fire of 300 °F for 3 seconds does not prevent the stored components from operating.


(6) A test shall be conducted to demonstrate that each structure resists puncture and tearing when tested in accordance with ASTM D2582-07 “Standard Test Method for Puncture-Propagation Tear Resistance of Plastic Film and Thin Sheeting.” This publication is incorporated by reference. The Director of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. A copy may be obtained from the American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; 610-832-9500; http://www.astm.org. A copy may be inspected at any MSHA Coal Mine Safety and Health District Office; or at MSHA’s Office of Standards, Regulations, and Variances, 201 12th Street South, Arlington, VA 22202-5452; 202-693-9440; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.


(7) A test shall be conducted to demonstrate that each reasonably anticipated repair can be completed within 10 minutes of opening the storage space for repair materials and tools.


(8) A test shall be conducted to demonstrate that no harmful gases or noticeable odors are released from nonmetallic materials before or after the flash fire test. The test shall identify the gases released and determine their concentrations.


(c) If pressurized air is used to deploy the structure or maintain its shape, the structure shall –


(1) Include a pressure regulator or other means to prevent over pressurization of the structure, and


(2) Provide a means to repair and re-pressurize the structure in case of failure of the structure or loss of air pressure.


(d) The refuge alternative structure shall provide a means –


(1) To conduct a preshift examination, without entering the structure, of components critical for deployment; and


(2) To indicate unauthorized entry or tampering.


[73 FR 80694, Dec. 31, 2008, as amended at 80 FR 52985, Sept. 2, 2015]


§ 7.506 Breathable air components.

(a) Breathable air shall be supplied by compressed air cylinders, compressed breathable-oxygen cylinders, or boreholes with fans installed on the surface or compressors installed on the surface. Only uncontaminated breathable air shall be supplied to the refuge alternative.


(b) Mechanisms shall be provided and procedures shall be included so that, within the refuge alternative, –


(1) The breathable air sustains each person for 96 hours,


(2) The oxygen concentration is maintained at levels between 18.5 and 23 percent, and


(3) The average carbon dioxide concentration is 1.0 percent or less and excursions do not exceed 2.5 percent.


(c) Breathable air supplied by compressed air from cylinders, fans, or compressors shall provide a minimum flow rate of 12.5 cubic feet per minute of breathable air for each person.


(1) Fans or compressors shall meet the following:


(i) Be equipped with a carbon monoxide detector located at the surface that automatically provides a visual and audible alarm if carbon monoxide in supplied air exceeds 10 parts per million (ppm).


(ii) Provide in-line air-purifying sorbent beds and filters or other equivalent means to assure the breathing air quality and prevent condensation, and include maintenance instructions that provide specifications for periodic replacement or refurbishment.


(iii) Provide positive pressure and an automatic means to assure that the pressure is relieved at 0.18 psi, or as specified by the manufacturer, above mine atmospheric pressure in the refuge alternative.


(iv) Include warnings to assure that only uncontaminated breathable air is supplied to the refuge alternative.


(v) Include air lines to supply breathable air from the fan or compressor to the refuge alternative.


(A) Air lines shall be capable of preventing or removing water accumulation.


(B) Air lines shall be designed and protected to prevent damage during normal mining operations, a flash fire of 300 °F for 3 seconds, a pressure wave of 15 psi overpressure for 0.2 seconds, and ground failure.


(vi) Assure that harmful or explosive gases, water, and other materials cannot enter the breathable air.


(2) Redundant fans or compressors and power sources shall be provided to permit prompt re-activation of equipment in the event of failure.


(d) Compressed breathable oxygen shall –


(1) Include instructions for deployment and operation;


(2) Provide oxygen at a minimum flow rate of 1.32 cubic feet per hour per person;


(3) Include a means to readily regulate the pressure and volume of the compressed oxygen;


(4) Include an independent regulator as a backup in case of failure; and


(5) Be used only with regulators, piping, and other equipment that is certified and maintained to prevent ignition or combustion.


(e) The applicant shall prepare and submit an analysis or study demonstrating that the breathable air component will not cause an ignition.


(1) The analysis or study shall specifically address oxygen fire hazards and fire hazards from chemicals used for removal of carbon dioxide.


(2) The analysis or study shall identify the means used to prevent any ignition source.


§ 7.507 Air-monitoring components.

(a) Each refuge alternative shall have an air-monitoring component that provides persons inside with the ability to determine the concentrations of carbon dioxide, carbon monoxide, oxygen, and methane, inside and outside the structure, including the airlock.


(b) Refuge alternatives designed for use in mines with a history of harmful gases, other than carbon monoxide, carbon dioxide, and methane, shall be equipped to measure the harmful gases’ concentrations.


(c) The air-monitoring component shall be inspected or tested and the test results shall be included in the application.


(d) The air-monitoring component shall meet the following:


(1) The total measurement error, including the cross-sensitivity to other gases, shall not exceed ±10 percent of the reading, except as specified in the approval.


(2) The measurement error limits shall not be exceeded after start-up, after 8 hours of continuous operation, after 96 hours of storage, and after exposure to atmospheres with a carbon monoxide concentration of 999 ppm (full-scale), a carbon dioxide concentration of 3 percent, and full-scale concentrations of other gases.


(3) Calibration gas values shall be traceable to the National Institute for Standards and Technology (NIST) “Standard Reference Materials” (SRMs).


(4) The analytical accuracy of the calibration gas and span gas values shall be within 2.0 percent of NIST gas standards.


(5) The detectors shall be capable of being kept fully charged and ready for immediate use.


§ 7.508 Harmful gas removal components.

(a) Each refuge alternative shall include means for removing harmful gases.


(1) Purging or other effective procedures shall be provided for the airlock to dilute the carbon monoxide concentration to 25 ppm or less and the methane concentration to 1.0 percent or less as persons enter, within 20 minutes of persons deploying the refuge alternative.


(2) Chemical scrubbing or other effective procedures shall be provided so that the average carbon dioxide concentration in the occupied structure shall not exceed 1.0 percent over the rated duration, and excursions shall not exceed 2.5 percent.


(i) Carbon dioxide removal components shall be used with breathable air cylinders or oxygen cylinders.


(ii) Carbon dioxide removal components shall remove carbon dioxide at a rate of 1.08 cubic feet per hour per person.


(3) Instructions shall be provided for deployment and operation of the harmful gas removal component.


(b) The harmful gas removal component shall meet the following requirements: Each chemical used for removal of harmful gas shall be –


(1) Contained such that when stored or used it cannot come in contact with persons, and it cannot release airborne particles.


(2) Provided with all materials; parts, such as hangers, racks, and clips; equipment; and instructions necessary for deployment and use.


(3) Stored in an approved container that is conspicuously marked with the manufacturer’s instructions for disposal of used chemical.


(c) Each harmful gas removal component shall be tested to determine its ability to remove harmful gases.


(1) The component shall be tested in a refuge alternative structure that is representative of the configuration and maximum volume for which the component is designed.


(i) The test shall include three sampling points located vertically along the centerlines of the length and width of the structure and equally spaced over the horizontal centerline of the height of the structure.


(ii) The structure shall be sealed airtight.


(iii) The operating gas sampling instruments shall be placed inside the structure and continuously exposed to the test atmosphere.


(iv) Sampling instruments shall simultaneously measure the gas concentrations at the three sampling points.


(2) For testing the component’s ability to remove carbon monoxide, the structure shall be filled with a test gas of either purified synthetic air or purified nitrogen that contains 400 ppm carbon monoxide, ±5 percent.


(i) After a stable concentration of 400 ppm, ±5 percent, carbon monoxide has been obtained for 5 minutes at all three sampling points, a timer shall be started and the structure shall be purged or carbon monoxide otherwise removed.


(ii) Carbon monoxide concentration readings from each of the three sampling instruments shall be recorded every 2 minutes.


(iii) The time shall be recorded from the start of harmful gas removal until the readings of the three sampling instruments all indicate a carbon monoxide concentration of 25 ppm or less.


(3) For testing the component’s ability to remove carbon dioxide, the carbon dioxide concentration shall not exceed 1.0 percent over the rated duration and excursions shall not exceed 2.5 percent under the following conditions:


(i) At 55 °F (±4 °F), 1 atmosphere (±1 percent), and 50 percent (±5 percent) relative humidity.


(ii) At 55 °F (±4 °F), 1 atmosphere (±1 percent), and 100 percent (±5 percent) relative humidity.


(iii) At 90 °F (±4 °F), 1 atmosphere (±1 percent), and 50 percent (±5 percent) relative humidity.


(iv) At 82 °F (±4 °F), 1 atmosphere (±1 percent), and 100 percent (±5 percent) relative humidity.


(4) Testing shall demonstrate the component’s continued ability to remove harmful gases effectively throughout its designated shelf-life, specifically addressing the effects of storage and transportation.


(d) Alternate performance tests may be conducted if the tests provide the same level of assurance of the harmful gas removal component’s capability as the tests specified in paragraph (c) of this section. Alternate tests shall be specified in the approval application.


§ 7.509 Approval markings.

(a) Each approved refuge alternative or component shall be identified by a legible, permanent approval marking that is securely and conspicuously attached to the component or its container.


(b) The approval marking shall be inscribed with the component’s MSHA approval number and any additional markings required by the approval.


(c) The refuge alternative structure shall provide a conspicuous means for indicating an out-of-service status, including the reason it is out of service.


(d) The airlock shall be conspicuously marked with the recommended maximum number of persons that can use it at one time.


§ 7.510 New technology.

MSHA may approve a refuge alternative or a component that incorporates new knowledge or technology, if the applicant demonstrates that the refuge alternative or component provides no less protection than those meeting the requirements of this subpart.


PART 14 – REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS


Authority:30 U.S.C. 957.


Source:73 FR 80609, Dec. 31, 2008, unless otherwise noted.

Subpart A – General Provisions

§ 14.1 Purpose, effective date for approval holders.

This Part establishes the flame resistance requirements for MSHA approval of conveyor belts for use in underground coal mines. Applications for approval or extensions of approval submitted after December 31, 2008, must meet the requirements of this Part.


§ 14.2 Definitions.

The following definitions apply in this part:


Applicant. An individual or organization that manufactures or controls the production of a conveyor belt and applies to MSHA for approval of conveyor belt for use in underground coal mines.


Approval. A document issued by MSHA, which states that a conveyor belt has met the requirements of this Part and which authorizes an approval marking identifying the conveyor belt as approved.


Extension of approval. A document issued by MSHA, which states that a change to a product previously approved by MSHA meets the requirements of this Part and which authorizes the continued use of the approval marking after the appropriate extension number has been added.


Flame-retardant ingredient. A material that inhibits ignition or flame propagation.


Flammable ingredient. A material that is capable of combustion.


Inert ingredient. A material that does not contribute to combustion.


Post-approval product audit. An examination, testing, or both, by MSHA of an approved conveyor belt selected by MSHA to determine if it meets the technical requirements and has been manufactured as approved.


Similar conveyor belt. A conveyor belt that shares the same cover compound, general carcass construction, and fabric type as another approved conveyor belt.


§ 14.3 Observers at tests and evaluations.

Representatives of the applicant and other persons agreed upon by MSHA and the applicant may be present during tests and evaluations conducted under this Part. However, if MSHA receives a request from others to observe tests, the Agency will consider it.


§ 14.4 Application procedures and requirements.

(a) Application address. Applications for approvals or extensions of approval under this Part may be sent to: U.S. Department of Labor, Mine Safety and Health Administration, Chief, Approval and Certification Center, 765 Technology Drive, Triadelphia, West Virginia 26059. Alternatively, applications for approval or extensions of approval may be filed online at http://www.msha.gov or faxed to: Chief, Mine Safety and Health Administration Approval and Certification Center at 304-547-2044.


(b) Approval application. Each application for approval of a conveyor belt for use in underground coal mines must include the information below, except any information submitted in a prior approval application need not be re-submitted, but must be noted in the application.


(1) A technical description of the conveyor belt, which includes:


(i) Trade name or identification number;


(ii) Cover compound type and designation number;


(iii) Belt thickness and thickness of top and bottom covers;


(iv) Presence and type of skim coat;


(v) Presence and type of friction coat;


(vi) Carcass construction (number of plies, solid woven);


(vii) Carcass fabric by textile type and weight (ounces per square yard);


(viii) Presence and type of breaker or floated ply; and


(ix) The number, type, and size of cords and fabric for metal cord belts.


(2) The name, address, and telephone number of the applicant’s representative responsible for answering any questions regarding the application.


(c) Similar belts and extensions of approval may be evaluated for approval without testing using the BELT method if the following information is provided in the application:


(1) Formulation information on the compounds in the conveyor belt indicated by either:


(i) Specifying each ingredient by its chemical name along with its percentage (weight) and tolerance or percentage range; or


(ii) Specifying each flame-retardant ingredient by its chemical or generic name with its percentage and tolerance or percentage range or its minimum percent. List each flammable ingredient and inert ingredient by chemical, generic, or trade name along with the total percentage of all flammable and inert ingredients.


(2) Identification of any similar approved conveyor belt for which the applicant already holds an approval, and the formulation specifications for that belt if it has not previously been submitted to the Agency.


(i) The MSHA assigned approval number of the conveyor belt that most closely resembles the new one; and


(ii) An explanation of any changes from the existing approval.


(d) Extension of approval. Any change in an approved conveyor belt from the documentation on file at MSHA that affects the technical requirements of this Part must be submitted for approval prior to implementing the change. Each application for an extension of approval must include:


(1) The MSHA-assigned approval number for the conveyor belt for which the extension is sought;


(2) A description of the proposed change to the conveyor belt; and


(3) The name, address, and telephone number of the applicant’s representative responsible for answering any questions regarding the application.


(e) MSHA will determine if testing, additional information, samples, or material is required to evaluate an application. If the applicant believes that flame testing is not required, a statement explaining the rationale must be included in the application.


(f) Equivalent non-MSHA product safety standard. An applicant may request an equivalency determination to this part under § 6.20 of this chapter, for a non-MSHA product safety standard.


(g) Fees. Fees calculated in accordance with Part 5 of this chapter must be submitted in accordance with § 5.40.


§ 14.5 Test samples.

Upon request by MSHA, the applicant must submit 3 precut, unrolled, flat conveyor belt samples for flame testing. Each sample must be 60 ±
1/4 inches long (152.4 ±0.6 cm) by 9 ±
1/8 inches (22.9 ±0.3 cm) wide.


§ 14.6 Issuance of approval.

(a) MSHA will issue an approval or notice of the reasons for denying approval after completing the evaluation and testing provided in this part.


(b) An applicant must not advertise or otherwise represent a conveyor belt as approved until MSHA has issued an approval.


§ 14.7 Approval marking and distribution records.

(a) An approved conveyor belt must be marketed only under the name specified in the approval.


(b) Approved conveyor belt must be legibly and permanently marked with the assigned MSHA approval number for the service life of the product. The approval marking must be at least
1/2 inch (1.27 cm) high, placed at intervals not to exceed 60 feet (18.3 m) and repeated at least once every foot (0.3 m) across the width of the belt.


(c) Where the construction of a conveyor belt does not permit marking as prescribed above, other permanent marking may be accepted by MSHA.


(d) Applicants granted approval must maintain records of the initial sale of each belt having an approval marking. The records must be retained for at least 5 years following the initial sale.


§ 14.8 Quality assurance.

Applicants granted an approval or an extension of approval under this Part must:


(a) In order to assure that the finished conveyor belt will meet the flame-resistance test –


(1) Flame test a sample of each batch, lot, or slab of conveyor belts; or


(2) Flame test or inspect a sample of each batch or lot of the materials that contribute to the flame-resistance characteristic.


(b) Calibrate instruments used for the inspection and testing in paragraph (a) of this section according to the instrument manufacturer’s specifications. Instruments must be calibrated using standards set by the National Institute of Standards and Technology, U.S. Department of Commerce or other nationally or internationally recognized standards. The instruments used must be accurate to at least one significant figure beyond the desired accuracy.


(c) Control production so that the conveyor belt is manufactured in accordance with the approval document. If a third party is assembling or manufacturing all or part of an approved belt, the approval holder shall assure that the product is manufactured as approved.


(d) Immediately notify the MSHA Approval and Certification Center of any information that a conveyor belt has been distributed that does not meet the specifications of the approval. This notification must include a description of the nature and extent of the problem, the locations where the conveyor belt has been distributed, and the approval holder’s plans for corrective action.


§ 14.9 Disclosure of information.

(a) All proprietary information concerning product specifications and performance submitted to MSHA by the applicant will be protected.


(b) MSHA will notify the applicant or approval holder of requests for disclosure of information concerning its conveyor belts, and provide an opportunity to present its position prior to any decision on disclosure.


§ 14.10 Post-approval product audit.

(a) Approved conveyor belts will be subject to periodic audits by MSHA to determine conformity with the technical requirements upon which the approval was based. MSHA will select an approved conveyor belt to be audited; the selected belt will be representative of that distributed for use in mines. Upon request to MSHA, the approval holder may obtain any final report resulting from the audit.


(b) No more than once a year, except for cause, the approval holder, at MSHA’s request, must make 3 samples of an approved conveyor belt of the size specified in § 14.5 available at no cost to MSHA for an audit. If a product is not available because it is not currently in production, the manufacturer will notify MSHA when it is available. Representatives of the applicant and other persons agreed upon by MSHA and the applicant may be present during audit tests and evaluations. MSHA will also consider requests by others to observe tests.


(c) A conveyor belt will be subject to audit for cause at any time MSHA believes the approval holder product is not in compliance with the technical requirements of the approval.


§ 14.11 Revocation.

(a) MSHA may revoke for cause an approval issued under this Part if the conveyor belt –


(1) Fails to meet the technical requirements; or


(2) Creates a danger or hazard when used in a mine.


(b) Prior to revoking an approval, the approval holder will be informed in writing of MSHA’s intention to revoke. The notice will –


(1) Explain the reasons for the proposed revocation; and


(2) Provide the approval holder an opportunity to demonstrate or achieve compliance with the product approval requirements.


(c) Upon request to MSHA, the approval holder will be given the opportunity for a hearing.


(d) If a conveyor belt poses an imminent danger to the safety or health of miners, an approval may be immediately suspended without written notice of the Agency’s intention to revoke.


Subpart B – Technical Requirements

§ 14.20 Flame resistance.

Conveyor belts for use in underground coal mines must be flame-resistant and:


(a) Tested in accordance with § 14.22 of this part; or


(b) Tested in accordance with an alternate test determined by MSHA to be equivalent under 30 CFR §§ 6.20 and 14.4(e).


§ 14.21 Laboratory-scale flame test apparatus.

The principal parts of the apparatus used to test for flame resistance of conveyor belts are as follows –


(a) A horizontal test chamber 66 inches (167.6 cm) long by 18 inches (45.7 cm) square (inside dimensions) constructed from 1 inch (2.5 cm) thick Marinite I ®, or equivalent insulating material.


(b) A 16-gauge (0.16 cm) stainless steel duct section which tapers over a length of at least 24 inches (61 cm) from a 20 inch (51 cm) square cross-sectional area at the test chamber connection to a 12 inch (30.5 cm) diameter exhaust duct, or equivalent. The interior surface of the tapered duct section must be lined with
1/2 inch (1.27 cm) thick ceramic blanket insulation, or equivalent insulating material. The tapered duct must be tightly connected to the test chamber.


(c) A U-shaped gas-fueled impinged jet burner ignition source, measuring 12 inches (30.5 cm) long and 4 inches (10.2 cm) wide, with two parallel rows of 6 jets each. Each jet is spaced alternately along the U-shaped burner tube. The 2 rows of jets are slanted so that they point toward each other and the flame from each jet impinges upon each other in pairs. The burner fuel must be at least 98 percent methane (technical grade) or natural gas containing at least 96 percent combustible gases, which includes not less than 93 percent methane.


(d) A removable steel rack, consisting of 2 parallel rails and supports that form a 7 ±
1/8 inches (17.8 ±0.3 cm) wide by 60 ±
1/8 inches (152.4 ±0.3 cm) long assembly to hold a belt sample.


(1) The 2 parallel rails, with a 5 ±
1/8 inches (12.7 ±0.3 cm) space between them, comprise the top of the rack. The rails and supports must be constructed of slotted angle iron with holes along the top surface.


(2) The top surface of the rack must be 8 ±
1/8 inches (20.3 ±0.3 cm) from the inside roof of the test chamber.


§ 14.22 Test for flame resistance of conveyor belts.

(a) Test procedures. The test must be conducted in the following sequence using a flame test apparatus meeting the specifications of § 14.21:


(1) Lay three samples of the belt, 60 ±
1/4 inches (152.4 ±0.6 cm) long by 9 ±
1/8 inches (22.9 ±0.3 cm) wide, flat at a temperature of 70 ±10 °Fahrenheit (21 ±5 °Centigrade) for at least 24 hours prior to the test;


(2) For each of three tests, place one belt sample with the load-carrying surface facing up on the rails of the rack so that the sample extends 1 ±
1/8 inch (2.5 ±0.3 cm) beyond the front of the rails and 1 ±
1/8 inch (2.5 ±0.3 cm) from the outer lengthwise edge of each rail;


(3) Fasten the sample to the rails of the rack with steel washers and cotter pins. The cotter pins shall extend at least
3/4 inch (1.9 cm) below the rails. Equivalent fasteners may be used. Make a series of 5 holes approximately
9/32 inch (0.7 cm) in diameter along both edges of the belt sample, starting at the first rail hole within 2 inches (5.1 cm) from the front edge of the sample. Make the next hole 5 ±
1/4 inches (12.7 ±0.6 cm) from the first, the third hole 5 ±
1/4 inches (12.7 ±0.6 cm) from the second, the fourth hole approximately midway along the length of the sample, and the fifth hole near the end of the sample. After placing a washer over each sample hole, insert a cotter pin through the hole and spread it apart to secure the sample to the rail;


(4) Center the rack and sample in the test chamber with the front end of the sample 6 ±
1/2 inches (15.2 ±1.27 cm) from the entrance;


(5) Measure the airflow with a 4-inch (10.2 cm) diameter vane anemometer, or an equivalent device, placed on the centerline of the belt sample 12 ±
1/2 inches (30.5 ±1.27 cm) from the chamber entrance. Adjust the airflow passing through the chamber to 200 ±20 ft/min (61 ±6 m/min);


(6) Before starting the test on each sample, the inner surface temperature of the chamber roof measured at points 6 ±
1/2, 30 ±
1/2, and 60 ±
1/2 inches (15.2 ±1.27, 76.2 ±1.27, and 152.4 ±1.27 cm) from the front entrance of the chamber must not exceed 95 °Fahrenheit (35 °Centigrade) at any of these points with the specified airflow passing through the chamber. The temperature of the air entering the chamber during the test on each sample must not be less than 50 °Fahrenheit (10 °Centigrade);


(7) Center the burner in front of the sample’s leading edge with the plane, defined by the tips of the burner jets,
3/4 ±
1/8 inch (1.9 ±0.3 cm) from the front edge of the belt;


(8) With the burner lowered away from the sample, set the gas flow at 1.2 ±0.1 standard cubic feet per minute (SCFM) (34 ±2.8 liters per minute) and then ignite the gas burner. Maintain the gas flow to the burner throughout the 5 to 5.1 minute ignition period;


(9) After applying the burner flame to the front edge of the sample for a 5 to 5.1 minute ignition period, lower the burner away from the sample and extinguish the burner flame;


(10) After completion of each test, determine the undamaged portion across the entire width of the sample. Blistering without charring does not constitute damage.


(b) Acceptable performance. Each tested sample must exhibit an undamaged portion across its entire width.


(c) MSHA may modify the procedures of the flammability test for belts constructed of thicknesses more than
3/4 inch (1.9 cm).


§ 14.23 New technology.

MSHA may approve a conveyor belt that incorporates technology for which the requirements of this part are not applicable if the Agency determines that the conveyor belt is as safe as those which meet the requirements of this part.


PART 15 – REQUIREMENTS FOR APPROVAL OF EXPLOSIVES AND SHEATHED EXPLOSIVE UNITS


Authority:30 U.S.C. 957.


Source:53 FR 46761, Nov. 18, 1988, unless otherwise noted.

Subpart A – General Provisions

§ 15.1 Purpose and effective dates.

This part sets forth the requirements for approval of explosives and sheathed explosive units to be used in underground coal mines and certain underground metal and nonmetal gassy mines and is effective January 17, 1989. Those manufacturers proceeding under the provisions of the previous regulation may file requests for approval or extension of approval of explosives under that regulation until January 17, 1990. After January 17, 1990, all requests for approval or extension of approval of explosives or sheathed explosive units shall be made in accordance with Subpart A and the applicable subpart of this part. Explosives issued an approval under regulations in place prior to January 17, 1989, and in compliance with those regulations, may continue to be manufactured and marked as approved as long as no change to the explosive is made.


[53 FR 46761, Nov. 18, 1988; 54 FR 351, Jan. 5, 1989]


§ 15.2 Definitions.

The following definitions apply in this part.


Applicant. An individual or organization that manufactures or controls the production of an explosive or an explosive unit and that applies to MSHA for approval of that explosive or explosive unit.


Approval. A document issued by MSHA which states that an explosive or explosive unit has met the requirements of this part and which authorizes an approval marking identifying the explosive or explosive unit as approved as permissible.


Explosive. A substance, compound, or mixture, the primary purpose of which is to function by explosion.


Extension of approval. A document issued by MSHA which states that the change to an explosive or explosive unit previously approved by MSHA under this part meets the requirements of this part and which authorizes the continued use of the approval marking after the appropriate extension number has been added.


Minimum product firing temperature. The lowest product temperature at which the explosive or explosive unit is approved for use under this part.


Post-approval product audit. Examination, testing, or both, by MSHA of approved explosives or explosive units selected by MSHA to determine whether they meet the technical requirements and have been manufactured as approved.


Sheath. A chemical compound or mixture incorporated in a sheathed explosive unit and which forms a flame inhibiting cloud on detonation of the explosive.


Sheathed explosive unit. A device consisting of an approved or permissible explosive covered by a sheath encased in a sealed covering and designed to be fired outside the confines of a borehole.


Test detonator. An instantaneous detonator that has a strength equivalent to that of a detonator with a base charge of 0.40-0.45 grams PETN.


[53 FR 46761, Nov. 18, 1988; 54 FR 351, Jan. 5, 1989]


§ 15.3 Observers at tests and evaluation.

Only personnel of MSHA, designees of MSHA, representatives of the applicant, and such other persons as agreed upon by MSHA and the applicant shall be present during tests and evaluations conducted under this part.


[70 FR 46342, Aug. 9, 2005]


§ 15.4 Application procedures and requirements.

(a) Application. Requests for an approval or an extension of approval under this part shall be sent to: U.S. Department of Labor, Mine Safety and Health Administration, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059.


(b) Fees. Fees calculated in accordance with Part 5 of this Title shall be submitted in accordance with § 5.40.


(c) Original approval for explosives. Each application for approval of an explosive shall include –


(1) A technical description of the explosive, including the chemical composition of the explosive with tolerances for each ingredient;


(2) A laboratory number or other suitable designation identifying the explosive. The applicant shall provide the brand or trade name under which the explosive will be marketed prior to issuance of the approval;


(3) The lengths and diameters of explosive cartridges for which approval is requested;


(4) The proposed minimum product firing temperature of the explosive; and


(5) The name, address, and telephone number of the applicant’s representative responsible for answering any questions regarding the application.


(d) Original approval for sheathed explosive units. Each application for approval of a sheathed explosive unit shall include –


(1) A technical description of the sheathed explosive unit which includes the chemical composition of the sheath, with tolerances for each ingredient, and the types of material used for the outer covering;


(2) The minimum thickness weight, and specific gravity of the sheath and outer covering;


(3) The brand or trade name, weight, specific gravity, and minimum product firing temperature of the approved explosive to be used in the unit;


(4) The ratio of the weight of the sheath to the weight of the explosive; and


(5) The name, address and telephone number of the applicant’s representative responsible for answering any questions regarding the application.


(e) Subsequent approval of a similar explosive or sheathed explosive unit. Each application for approval of an explosive or sheathed explosive unit similar to one for which the applicant already holds an approval shall include –


(1) The approval number of the explosive or sheathed explosive unit which most closely resembles the new one;


(2) The information specified in paragraphs (c) and (d) of this section for an original approval, as applicable, except that any document which is the same as the one listed by MSHA in the prior approval need not be submitted but shall be noted in the application; and


(3) An explanation of all changes from the existing approval.


(f) Extension of the approval. Any change in an approved explosive or sheathed explosive unit from the documentation on file at MSHA that affects the technical requirements of this Part shall be submitted for approval prior to implementing the change.


(1) Each application for an extension of approval shall include –


(i) The MSHA-assigned approval number for the explosive or sheathed explosive unit for which the extension is sought;


(ii) A description of the proposed change to the approved explosive or sheathed explosive unit; and


(iii) The name, address, and telephone number of the applicant’s representative responsible for answering any questions regarding the application.


(2) MSHA will determine what tests, additional information, samples, or material, if any, are required to evaluate the proposed change.


(3) When a change involves the chemical composition of an approved explosive or sheathed explosive unit which affects the firing characteristics, MSHA may require the explosive or sheathed explosive unit to be distinguished from those associated with the former composition.


[53 FR 46761, Nov. 18, 1988; 54 FR 351, Jan. 5, 1989; 60 FR 33723, June 29, 1995; 73 FR 52211, Sept. 9, 2008]


§ 15.5 Test samples.

(a) Submission of test samples. (1) The applicant shall not submit explosives or sheathed explosive units to be tested until requested to do so by MSHA.


(2) The applicant shall submit 70 pounds of 1
1/4-inch diameter explosives and additional cartridges in the amount of 3200 divided by the length in inches, except for cartridges 12, 20 and greater than 36 inches long. The applicant shall submit 70 pounds and additional cartridges in the amount of 3800 divided by the length in inches for cartridges 12, 20 and greater than 36 inches long.


(3) If approval is requested for cartridges in diameters less than 1-
1/4 inches, the applicant shall submit a number of cartridges equal to 1800 divided by the length in inches, except for cartridges 12, 20 and greater than 36 inches long. The applicant shall submit cartridges in the amount of 2200 divided by the length in inches for cartridges 12, 20 and greater than 36 inches long.


(4) If approval is requested for cartridges in diameters larger than 1-
1/4 inches, the applicant shall submit an additional 10 cartridges of each larger diameter.


(5) If approval is requested for cartridges in more than one length, the applicant shall submit an additional 10 cartridges for each additional length and diameter combination.


(6) Each applicant seeking approval of sheathed explosive units shall submit 140 units.


(b) Condition and composition. Explosives and sheathed explosive units will not be tested that –


(1) Contain chlorites, chlorates, or substances that will react over an extended time and cause degradation of the explosive or sheathed explosive unit;


(2) Are chemically unstable;


(3) Show leakage;


(4) Use aluminum clips to seal the cartridge;


(5) Contain any combination of perchlorate and aluminum;


(6) Contain more than 5 percent perchlorate; or


(7) Contain any perchlorate and less than 5 percent water.


(c) Storage. Explosives and sheathed explosive units shall be stored in a magazine for at least 30 days before gallery tests are conducted.


§ 15.6 Issuance of approval.

(a) MSHA will issue an approval or a notice of the reasons for denying approval after completing the evaluation and testing provided for by this part.


(b) An applicant shall not advertise or otherwise represent an explosive or sheathed explosive unit as approved until MSHA has issued an approval.


§ 15.7 Approval marking.

(a) An approved explosive or sheathed explosive unit shall be marketed only under the brand or trade name specified in the approval.


(b) The wrapper of each cartridge and each case of approved explosives shall be legibly labeled with the following: the brand or trade name, “MSHA Approved Explosive”, the test detonator strength, and the minimum product firing temperature.


(c) The outer covering of each sheathed explosive unit and each case of approved sheathed explosive units shall be legibly labeled with the following: the brand or trade name, “MSHA Approved Sheathed Explosive Unit”, the test detonator strength, and the minimum product firing temperature.


[53 FR 46761, Nov. 18, 1988; 54 FR 351, Jan. 5, 1989; 54 FR 27641, June 30, 1989; 60 FR 33723, June 29, 1995]


§ 15.8 Quality assurance.

(a) Applicants granted an approval or an extension of approval under this part shall manufacture the explosive or sheathed explosive unit as approved.


(b) Applicants shall immediately report to the MSHA Approval and Certification Center, any knowledge of explosives or sheathed explosive units that have been distributed that do not meet the specifications of the approval.


[53 53 FR 46761, Nov. 18, 1988, as amended at 60 FR 33723, June 29, 1995]


§ 15.9 Disclosure of information.

(a) All information concerning product specifications and performance submitted to MSHA by the applicant shall be considered proprietary information.


(b) MSHA will notify the applicants of requests for disclosure of information concerning its explosives or sheathed explosive units and shall give the applicant an opportunity to provide MSHA with a statement of its position prior to any disclosure.


§ 15.10 Post-approval product audit.

(a) Approved explosives and sheathed explosive units shall be subject to periodic audits by MSHA for the purpose of determining conformity with the technical requirements upon which the approval was based. Any approved explosive or sheathed explosive unit which is to be audited shall be selected by MSHA and be representative of those distributed for use in mines. The approval-holder may obtain any final report resulting from such audit.


(b) No more than once a year, except for cause, the approval-holder, at MSHA’s request, shall make one case of explosives or 25 sheathed explosive units available at no cost to MSHA for an audit. The approval-holder may observe any tests conducted during this audit.


(c) An approved explosive or sheathed explosive unit shall be subject to audit for cause at any time MSHA believes that it is not in compliance with the technical requirements upon which the approval was based.


(d) Explosives approved under regulations in effect prior to January 17, 1989, shall conform to the provisions on field samples set out in those regulations (See 30 CFR part 15, 1987 edition).


§ 15.11 Revocation.

(a) MSHA may revoke for cause an approval issued under this part if the explosive or sheathed explosive unit –


(1) Fails to meet the applicable technical requirements; or


(2) Creates a hazard when used in a mine.


(b) Prior to revoking an approval, the approval-holder shall be informed in writing of MSHA’s intention to revoke. The notice shall –


(1) Explain the specific reasons for the proposed revocation; and


(2) Provide the approval-holder an opportunity to demonstrate or achieve compliance with the product approval requirements.


(c) Upon request, the approval-holder shall be afforded an opportunity for a hearing.


(d) If an explosive or sheathed explosive unit poses an imminent hazard to the safety or health of miners, the approval may be immediately suspended without a written notice of the agency’s intention to revoke. The suspension may continue until the revocation proceedings are completed.


Subpart B – Requirements for Approval of Explosives

§ 15.20 Technical requirements.

(a) Chemical composition. The chemical composition of the explosive shall be within the tolerances furnished by the applicant.


(b) Rate-of-detonation test. The explosive shall propagate completely in the rate-of-detonation test. The test is conducted at an ambient temperature between 68 and 86 °F. Nongelatinous explosives are initiated with a test detonator only, while gelatinous explosives are initiated with a test detonator and a 60-gram tetryl pellet booster. The test is conducted on –


(1) A 50-inch column of 1
1/4 inch diameter cartridges; and


(2) A 50-inch column of the smallest diameter cartridges less than 1
1/4 inches submitted for testing.


(c) Air-gap sensitivity. The air-gap sensitivity of the explosive shall be at least 2 inches at the minimum product firing temperature and 3 inches at a temperature between 68 and 86 °F, and the explosive shall propagate completely.


(1) Air-gap sensitivity of the explosive is determined in the explosion-by-influence test using the 7-inch cartridge method. The air-gap sensitivity is determined for 1
1/4 inch diameter cartridges and each cartridge diameter smaller than 1
1/4 inches. Explosives are initiated with a test detonator.


(2) The 7-inch cartridge method is conducted with two 8-inch cartridges. One inch is cut off the end of each cartridge. The cartridges are placed in a paper tube, the cut ends facing each other, with the appropriate 2-inch or 3-inch air gap between them. The test is conducted at a temperature between 68 and 86 °F and at the minimum product firing temperature proposed by the applicant, or 41 °F, whichever is lower. The test temperature at which the explosive propagates completely will be specified in the approval as the minimum product firing temperature at which the explosive is approved for use.


(d) Gallery Test 7. The explosive shall yield a value of at least 450 grams for the lower 95 percent confidence limit (L95) on the weight for 50 percent probability of ignition (W50) in gallery test 7 and shall propagate completely. The L95 and W50 values for the explosive are determined by using the Bruceton up-and-down method. A minimum of 20 trials are made with explosive charges of varying weights, including wrapper and seals. Each charge is primed with a test detonator, then tamped and stemmed with one pound of dry-milled fire clay into the borehole of a steel cannon. The cannon is fired into air containing 7.7 to 8.3 percent of natural gas. The air temperature is between 68 and 86 °F.


(e) Gallery Test 8. The explosive shall yield a value of at least 350 grams for the weight for 50 percent probability of ignition (WCDG) in gallery test 8 and shall propagate completely. The (WCDG) value for the explosive is determined using the Bruceton up-and-down method. A minimum of 10 tests are made with explosive charges of varying weights, including wrapper and seals. Each charge is primed with a test detonator, then tamped into the borehole of a steel cannon. The cannon is fired into a mixture of 8 pounds of bituminous coal dust predispersed into 640 cubic feet of air containing 3.8 to 4.2 percent of natural gas. The air temperature is between 68 and 86 °F.


(f) Pendulum-friction test. The explosive shall show no perceptible reaction in the pendulum-friction test with the hard fiber-faced shoe. Ten trials of the test are conducted by releasing the steel shoe from a height of 59 inches. If there is evidence of sensitivity, the test is repeated with the hard fiber-faced shoe.


(g) Toxic gases. The total volume equivalent to carbon monoxide (CO) of toxic gases produced by detonation of the explosive shall not exceed 2.5 cubic feet per pound of explosive as determined in the large chamber test. The explosive shall propagate completely.


(1) The large chamber test is conducted with a one-pound explosive charge, including wrapper and seal, primed with a test detonator. The explosive charge is loaded into the borehole of a steel cannon, then tamped and stemmed with one pound of dry-milled fire clay. The cannon is fired into the large chamber and the gaseous products resulting from detonation of the explosive are collected and analyzed for toxic gases. At least two trials are conducted.


(2) The equivalent volume of each toxic gas produced, relative to CO, is determined by multiplying the measured volume of the gas by a conversion factor. The conversion factor is equal to the threshold limit value, time weighted average (TLV-TWA) in parts-per-million for CO divided by the TLV-TWA for the toxic gas. The TLV-TWA conversion factor for each gas for which MSHA shall test is specified in Table I of this subpart. The total volume equivalent to CO of the toxic gases produced by detonation of the explosive is the sum of the equivalent volumes of the individual toxic gases.


Table I – Conversion Factors for Toxic Gases

[For Equivalent Volume Relative to Carbon Monoxide]


Toxic Gas
Conversion Factor
TLV-TWA (PPM)
Ammonia225
Carbon Dioxide0.015000
Carbon Monoxide150
Hydrogen Sulfide510
Nitric Oxide225
Nitrogen Dioxide173
Sulfur Dioxide252

(h) Cartridge diameter and length changes. (1) For proposed changes to an approved explosive involving only cartridge diameter or length, MSHA will determine what tests, if any, will be required.


(2) When a proposed change to an approved explosive involves a smaller diameter than that specified in the approval, the rate-of-detonation and air-gap sensitivity tests will be conducted.


(3) No test will be conducted on cartridges with diameters the same as or smaller than those that previously failed to detonate in the rate-of-detonation test.


(i) New technology. MSHA may approve an explosive that incorporates technology for which the requirements of this subpart are not applicable if MSHA determines that the explosive is as safe as those which meet the requirements of this subpart.


§ 15.21 Tolerances for ingredients.

Tolerances for each ingredient in an explosive, which are expressed as a percentage of the total explosive, shall not exceed the following:


(a) Physical sensitizers: The tolerances established by the applicant;


(b) Aluminum: ±0.7 percent;


(c) Carbonaceous materials: ±3 percent; and


(d) Moisture and ingredients other than specified in paragraphs (a), (b), and (c) of this section: The tolerances specified in Table II.


Table II – Tolerances for Moisture and Other Ingredients

Quantity of ingredients (as percent of total explosive or sheath)
Tolerance percent
0 to 5.01.2
5.1 to 10.01.5
10.1 to 20.01.7
20.1 to 30.02.0
30.1 to 40.02.3
40.1 to 50.02.5
50.1 to 55.02.8
55.1 to 100.03.0

§ 15.22 Tolerances for performance, wrapper, and specific gravity.

(a) The rate of detonation of the explosive shall be within ±15 percent of that specified in the approval.


(b) The weight of wrapper per 100 grams of explosive shall be within ±2 grams of that specified in the approval.


(c) The apparent specific gravity of the explosive shall be within ±7.5 percent of that specified in the approval.


Subpart C – Requirements for Approval of Sheathed Explosive Units or Other Explosive Units Designed to be Fired Outside the Confines of a Borehole

§ 15.30 Technical requirements.

(a) Quantity of explosive. The sheathed explosive unit shall contain not more than 1
1/2 pounds of an approved or permissible explosive.


(b) Chemical composition. The chemical composition of the sheath shall be within the tolerances furnished by the applicant.


(c) Detonator well. The sheathed explosive unit shall have a detonator well that –


(1) Is protected by a sealed covering;


(2) Permits an instantaneous detonator to be inserted in the unit with the detonator completely embedded in the well;


(3) Is provided with a means of securing the detonator in the well; and


(4) Is clearly marked.


(d) Drop test. The outer covering of the sheathed explosive unit shall not tear or rupture and the internal components shall not shift position or be damaged in the drop test.


(1) The drop test is conducted on at least 10 sheathed explosive units. Each unit is dropped on its top, bottom, and edge from a height of 6 feet onto a concrete surface. For units with explosives approved with a minimum product firing temperature, the drop test is performed with the unit at the minimum product firing temperature established for the explosive in the unit. For units with explosives approved under regulations in effect prior to January 17, 1989, the drop test is performed with the unit at 41 °F.


(2) At least four units which have been drop-tested shall be cut-open and examined.


(3) At least six units which have been drop-tested shall be subjected to gallery tests 9 and 10 as provided in paragraphs (e)(1) and (e)(2) of this section.


(e) Gallery tests. No sheathed explosive unit shall cause an ignition in gallery tests 9, 10, 11, or 12. Ten trials in each gallery test shall be conducted and each sheathed explosive unit shall propagate completely in all tests.


(1) Gallery test 9 is conducted in each trial with three sheathed explosive units placed in a row 2 feet apart. One of the trials is conducted with sheathed explosive units which have been subjected to the drop test as provided in paragraph (d)(3) of this section. The units are placed on a concrete slab, primed with test detonators and fired in air containing 7.7 to 8.3 percent natural gas or 8.7 to 9.3 percent methane. The air temperature is between 41 and 86 °F.


(2) Gallery test 10 is conducted in each trial with three sheathed explosive units placed in a row 2 feet apart. One of the trials is conducted with sheathed explosive units which have been subjected to the drop test as provided in paragraph (d)(3) of this section. The units are placed on a concrete slab, primed with test detonators and fired in air containing 3.8 to 4.2 percent natural gas, or 4.3 to 4.7 percent methane, mixed with 0.2 ounces per cubic foot of predispersed bituminous coal dust. The air temperature is between 41 and 86 °F.


(3) Gallery test 11 is conducted in each trial with three sheathed explosive units arranged in a triangular pattern with the units in contact with each other. The units are placed in a simulated crevice formed between two square concrete slabs, each measuring 24 inches on a side and 2 inches in thickness. The crevice is formed by placing one slab on top of the other and raising the edge of the upper slab at least 4 inches. The sheathed explosive units are primed with test detonators and fired in air containing 7.7 to 8.3 percent natural gas or 8.7 to 9.3 percent methane. The air temperature is between 41 and 86 °F.


(4) Gallery test 12 is conducted in each trial with three sheathed explosive units arranged in a triangular pattern with the units in contact with each other. The units are placed in a corner formed by three square steel plates, each measuring 24 inches on a side and one inch in thickness. The sheathed explosive units are primed with test detonators and fired in air containing 7.7 to 8.3 percent natural gas or 8.7 to 9.3 percent methane. The air temperature is between 41 and 86 °F.


(f) Detonation test. Each of ten sheathed explosive units shall propagate completely when fired at the minimum product firing temperature for the explosive used in the unit or 41 °F for units with explosives approved under regulations in effect prior to January 17, 1989. The units are initiated with test detonators.


(g) New technology. MSHA may approve an explosive unit designed to be fired outside the confines of a borehole that incorporates technology for which the requirements of this subpart are not applicable if MSHA determines that such explosive unit is as safe as those which meet the requirements of this subpart.


[53 FR 46761, Nov. 18, 1988; 54 FR 351, Jan. 5, 1989]


§ 15.31 Tolerances for ingredients.

Tolerances established by the applicant for each ingredient in the sheath shall not exceed the tolerances specified in Table II § 15.21 of this part.


§ 15.32 Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

(a) The weight of the explosive, the sheath, and the outer covering shall each be within ±7.5 percent of that specified in the approval.


(b) The ratio of the weight of the sheath to that of the explosive shall be within ±7.5 percent of that specified in the approval.


(c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified in the approval.


PART 18 – ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES


Authority:30 U.S.C. 957, 961.


Source:33 FR 4660, Mar. 19, 1968, unless otherwise noted.

Subpart A – General Provisions

§ 18.1 Purpose.

The regulations in this part set forth the requirements to obtain MSHA: Approval of electrically operated machines and accessories intended for use in gassy mines or tunnels, certification of components intended for use on or with approved machines, permission to modify the design of an approved machine or certified component, acceptance of flame-resistant hoses, sanction for use of experimental machines and accessories in gassy mines or tunnels; also, procedures for applying for such approval, certification, acceptance for listing.


[43 FR 12313, Mar. 24, 1978, as amended at 52 FR 17514, May 8, 1987; 57 FR 61223, Dec. 23, 1992; 73 FR 80611, Dec. 31, 2008]


§ 18.2 Definitions.

As used in this part –


Acceptance means written notification by MSHA that a hose has met the applicable requirements of this part and will be listed by MSHA as acceptable flame-resistant auxiliary equipment.


Acceptance marking means an identifying marking indicating that the hose has been accepted by MSHA for listing as flame resistant.


Accessory means associated electrical equipment, such as a distribution or splice box, that is not an integral part of an approved (permissible) machine.


Afterburning means the combustion of a flammable mixture that is drawn into a machine compartment after an internal explosion in the compartment.


Applicant means an individual, partnership, company, corporation, organization, or association that designs, manufactures, assembles, or controls the assembly of an electrical machine or accessory and seeks approval, certification, or permit, or MSHA acceptance for listing of flame-resistant hose.


Approval means a formal document issued by MSHA which states that a completely assembled electrical machine or accessory has met the applicable requirements of this part and which authorizes the attachment of an approval plate so indicating.


Approval plate means a metal plate, the design of which meets MSHA’s requirements, for attachment to an approved machine or accessory, identifying it as permissible for use in gassy mines or tunnels.


Assistant Secretary means the Assistant Secretary of Labor for Mine Safety and Health.


Branch circuit means an electrical circuit connected to the main circuit, the conductors of which are of smaller size than the main circuit.


Bureau means the U.S. Bureau of Mines.


Certification means a formal written notification, issued by MSHA, which states that an electrical component complies with the applicable requirements of this part and, therefore, is suitable for incorporation in approved (permissible) equipment.


Certification label means a plate, label, or marking, the design of which meets MSHA’s requirements, for attachment to a certified component identifying the component as having met the MSHA’s requirements for incorporation in a machine to be submitted for approval.


Component means an integral part of an electrical machine or accessory that is essential to the functioning of the machine or accessory.


Connection box (also known as conduit or terminal box) means an enclosure mounted on an electrical machine or accessory to facilitate wiring, without the use of external splices. (Such boxes may have a joint common with an explosion-proof enclosure provided the adjoining surfaces conform to the requirements of subpart B of this part.)


Cylindrical joint means a joint comprised of two contiguous, concentric, cylindrical surfaces.


Distribution box means an enclosure through which one or more portable cables may be connected to a source of electrical energy, and which contains a short-circuit protective device for each outgoing cable.


Experimental equipment means any electrical machine or accessory that an applicant or MSHA may desire to operate experimentally for a limited time in a gassy mine or tunnel. (For example, this might include a machine constructed at a mine, an imported machine, or a machine or device designed and developed by MSHA.)


Explosion-proof enclosure means an enclosure that complies with the applicable design requirements in subpart B of this part and is so constructed that it will withstand internal explosions of methane-air mixtures: (1) Without damage to or excessive distortion of its walls or cover(s), and (2) without ignition of surrounding methane-air mixtures or discharge of flame from inside to outside the enclosure.


Flame-arresting path means two or more adjoining or adjacent surfaces between which the escape of flame is prevented.


Flame resistant as applied to cable, hose, and insulating materials means material that will burn when held in a flame but will cease burning when the flame is removed.


Flammable mixture means a mixture of methane or natural gas and air that when ignited will propagate flame. Natural gas containing a high percentage of methane is a satisfactory substitute for pure methane in most tests.


Gassy mine means a coal mine classed as “gassy” by MESA or by the State in which the mine is situated.


Incendive arc or spark means an arc or spark releasing enough electrical or thermal energy to ignite a flammable mixture of the most easily ignitable composition.


Intrinsically safe means incapable of releasing enough electrical or thermal energy under normal or abnormal conditions to cause ignition of a flammable mixture of methane or natural gas and air of the most easily ignitable composition.


MESA means the United States Department of the Interior, Mining Enforcement and Safety Administration. Predecessor organization to MSHA, prior to March 9, 1978.


Mobile equipment means equipment that is self-propelled.


MSHA means the United States Department of Labor, Mine Safety and Health Administration.


Normal operation means the regular performance of those functions for which a machine or accessory was designed.


Permissible equipment means a completely assembled electrical machine or accessory for which a formal approval has been issued, as authorized by the Administrator, Mining Enforcement and Safety Administration under the Federal Coal Mine Health and Safety Act of 1969 (Pub. L. 91-173, 30 U.S.C. 801 or, after March 9, 1978, by the Assistant Secretary under the Federal Mine Safety and Health Act of 1977 (Pub. L. 91-173, as amended by Pub. L. 95-164, 30 U.S.C. 801).


Permit means a formal document, signed by the Assistant Secretary, authorizing the operation of specific experimental equipment in a gassy mine or tunnel under prescribed conditions.


Plane joint means two adjoining surfaces in parallel planes.


Portable cable, or trailing cable means a flame-resistant, flexible cable or cord through which electrical energy is transmitted to a permissible machine or accessory. (A portable cable is that portion of the power-supply system between the last short-circuit protective device, acceptable to MSHA, in the system and the machine or accessory to which it transmits electrical energy.)


Portable equipment means equipment that may be moved frequently and is constructed or mounted to facilitate such movement.


Potted component means a component that is entirely embedded in a solidified insulating material within an enclosure.


Pressure piling means the development of abnormal pressure as a result of accelerated rate of burning of a gas-air mixture. (Frequently caused by restricted configurations within enclosures.)


Qualified representative means a person authorized by MSHA to determine whether the applicable requirements of this part have been complied with in the original manufacture, rebuilding, or repairing of equipment for which approval, certification, or a permit is sought.


Splice box means a portable enclosure in which electrical conductors may be joined.


Step (rabbet) joint means a joint comprised of two adjoining surfaces with a change(s) in direction between its inner and outer edges. (A step joint may be composed of a cylindrical portion and a plane portion or of two or more plane portions.)


Threaded joint means a joint consisting of a male- and a female-threaded member, both of which are of the same type and gage.


[33 FR 4660, Mar. 19, 1968, as amended at 39 FR 23999, June 28, 1974; 43 FR 12314, Mar. 24, 1978; 57 FR 61223, Dec. 23, 1992; 73 FR 80611, Dec. 31, 2008]


§ 18.3 Consultation.

By appointment, applicants or their representatives may visit the U.S. Department of Labor, Mine Safety and Health Administration, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059, to discuss a proposed design to be submitted for approval, certification, or acceptance for listing. No charge is made for such consultation and no written report thereof will be made to the applicant.


[33 FR 4660, Mar. 19, 1968, as amended at 43 FR 12314, Mar. 24, 1978; 73 FR 52211, Sept. 9, 2008]


§ 18.4 Electrical equipment for which approval is issued.

An approval will be issued only for a complete electrical machine or accessory. Only components meeting the requirements of subpart B of this part or those approved under part 7 of this chapter, unless they contain intrinsically safe circuits, shall be included in the assemblies.


[57 FR 61209, Dec. 23, 1992]


§ 18.5 Equipment for which certification will be issued.

Certification will be issued for a component or subassembly suitable to incorporate in an approved machine. Certification may be issued for such components as explosion-proof enclosures, battery trays, and connectors.


§ 18.6 Applications.

(a)(1) Investigation leading to approval, certification, extension thereof, or acceptance of hose will be undertaken by MSHA only pursuant to a written application. The application shall be accompanied by all necessary drawings, specifications, descriptions, and related materials, as set out in this part. Fees calculated in accordance with part 5 of this title shall be submitted in accordance with § 5.40.


(2) Where the applicant for approval has used an independent testing laboratory under part 6 of this chapter to perform, in whole or in part, the necessary testing and evaluation for approval under this part, the applicant must provide to MSHA as part of the approval application:


(i) Written evidence of the laboratory’s independence and current recognition by a laboratory accrediting organization;


(ii) Complete technical explanation of how the product complies with each requirement in the applicable MSHA product approval requirements;


(iii) Identification of components or features of the product that are critical to the safety of the product; and


(iv) All documentation, including drawings and specifications, as submitted to the independent laboratory by the applicant and as required by this part.


(3) An applicant may request testing and evaluation to non-MSHA product safety standards which have been determined by MSHA to be equivalent, under § 6.20 of this chapter, to MSHA’s product approval requirements under this part. A listing of all equivalency determinations will be published in 30 CFR part 6 and the applicable approval parts. The listing will state whether MSHA accepts the non-MSHA product safety standards in their original form, or whether MSHA will require modifications to demonstrate equivalency. If modifications are required, they will be provided in the listing. MSHA will notify the public of each equivalency determination and will publish a summary of the basis for its determination. MSHA will provide equivalency determination reports to the public upon request to the Approval and Certification Center. MSHA has made the following equivalency determinations applicable to this part 18.


(i) MSHA will accept applications for explosion-proof enclosures under part 18 designed and tested to the International Electrotechnical Commission’s (IEC) standards for Electrical Apparatus for Explosive Gas Atmospheres, Part 0, General Requirements (IEC 60079-0, Fourth Edition, 2004-01); and Part 1, Electrical Apparatus for Explosive Gas Atmospheres, Flameproof Enclosures “d” (IEC 60079-1, Fifth Edition, 2003-11) (which are hereby incorporated by reference and made a part hereof) provided the modifications to the IEC standards specified in § 18.6(a)(3)(i)(A) through (I) are met. The Director of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. The IEC standards may be inspected at the U.S. Department of Labor, Mine Safety and Health Administration, Electrical Safety Division, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. These IEC standards may be obtained from International Electrical Commission, Central Office 3, rue de Varembé, P.O. Box 131, CH-1211 GENEVA 20, Switzerland.


(A) Enclosures shall be made of metal and not have a compartment exceeding ten (10) feet in length. Glass or polycarbonate materials shall be the only materials utilized in the construction of windows and lenses. External surfaces of enclosures shall not exceed 150 °C (302 °F) and internal surface temperatures of enclosures with polycarbonate windows and lenses shall not exceed 115 °C (240 °F), in normal operation. Other non-metallic materials for enclosures or parts of enclosures will be evaluated, on a case-by-case basis, under the new technology provisions in § 18.20(b) of this part.


(B) Enclosures shall be rugged in construction and should meet existing requirements for minimum bolt size and spacing and for minimum wall, cover, and flange thicknesses specified in paragraph (g)(19) of § 7.304 Technical requirements. Enclosure fasteners should be uniform in size and length, be provided at all corners, and be secured from loosening by lockwashers or equivalent. An engineering analysis shall be provided for enclosure designs that deviate from the existing requirements. The analysis shall show that the proposed enclosure design meets or exceeds the mechanical strength of a comparable enclosure designed to 150 psig according to existing requirements, and that flamepath clearances in excess of existing requirements will not be produced at an internal pressure of 150 psig. This shall be verified by explosion testing the enclosure at a minimum of 150 psig.


(C) Enclosures shall be designed to withstand a minimum pressure of at least 150 psig without leakage through any welds or castings, rupture of any part that affects explosion-proof integrity, clearances exceeding those permitted under existing requirements along flame-arresting paths, or permanent distortion exceeding 0.040-inch per linear foot.


(D) Flamepath clearances, including clearances between fasteners and the holes through which they pass, shall not exceed those specified in existing requirements. No intentional gaps in flamepaths are permitted.


(E) The minimum lengths of the flame arresting paths, based on enclosure volume, shall conform to those specified in existing requirements to the nearest metric equivalent value (e.g., 12.5 mm, 19 mm, and 25 mm are considered equivalent to
1/2 inch,
3/4 inch and 1 inch respectively for plane and cylindrical joints). The widths of any grooves for o-rings shall be deducted in measuring the widths of flame-arresting paths.


(F) Gaskets shall not be used to form any part of a flame-arresting path. If o-rings are installed within a flamepath, the location of the o-rings shall meet existing requirements.


(G) Cable entries into enclosures shall be of a type that utilizes either flame-resistant rope packing material or sealing rings (grommets). If plugs and mating receptacles are mounted to an enclosure wall, they shall be of explosion-proof construction. Insulated bushings or studs shall not be installed in the outside walls of enclosures. Lead entrances utilizing sealing compounds and flexible or rigid metallic conduit are not permitted.


(H) Unused lead entrances shall be closed with a metal plug that is secured by spot welding, brazing, or equivalent.


(I) Special explosion tests are required for explosion-proof enclosures that share leads (electric conductors) through a common wall with another explosion-proof enclosure. These tests are required to determine the presence of pressure piling conditions in either enclosure when one or more of the insulating barriers, sectionalizing terminals, or other isolating parts are sequentially removed from the common wall between the enclosures. Enclosures that exhibit pressures during these tests that exceed those specified in existing requirements must be provided with a warning tag. The durable warning tag must indicate that the insulating barriers, sectionalizing terminals, or other isolating parts be maintained in order to insure the explosion-proof integrity for either enclosure sharing a common wall. A warning tag is not required if the enclosures withstand a static pressure of twice the maximum value observed in the explosion tests.


(ii) [Reserved]


(4) The application, all related documents, and all correspondence concerning it shall be addressed to the U.S. Department of Labor, Mine Safety and Health Administration, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059.


(b)-(c) [Reserved]


(d) Applications for acceptance of hose as flame resistant shall include the following information: Trade name of hose, identification of materials used, including compound numbers, thickness of cover, thickness of tube, and number and weight of plies. The applicant shall provide other description or specifications as may be subsequently required.


(e) Drawings, drawing lists, specifications, wiring diagram, and descriptions shall be adequate in number and detail to identify fully the complete assembly, component parts, and subassemblies. Drawings shall be titled, numbered, dated and shall show the latest revision. Each drawing shall include a warning statement that changes in design must be authorized by MSHA before they are applied to approved equipment. When intrinsically safe circuits are incorporated in a machine or accessory, the wiring diagram shall include a warning statement that any change(s) in the intrinsically safe circuitry or components may result in an unsafe condition. The specifications shall include an assembly drawing(s) (see Figure 1 in Appendix II) showing the overall dimensions of the machine and the identity of each component part which may be listed thereon or separately, as in a bill of material (see Figure 2 in Appendix II). MSHA may accept photographs (minimum size 8″ × 10
1/2″) in lieu of assembly drawing(s). Purchased parts shall be identified by the manufacturer’s name, catalog number(s), and rating(s). In the case of standard hardware and miscellaneous parts, such as insulating pieces, size and kind of material shall be specified. All drawings of component parts submitted to MSHA shall be identical to those used in the manufacture of the parts. Dimensions of parts designed to prevent the passage of flame shall specify allowable tolerances. A notation “Do Not Drill Through” or equivalent should appear on drawings with the specifications for all “blind” holes.


(f) MSHA reserves the right to require the applicant to furnish supplementary drawings showing sections through complex flame-arresting paths, such as labyrinths used in conjunction with ball or roller bearings, and also drawings containing dimensions not indicated on other drawings submitted to MSHA.


(g) The applicant may ship his equipment to MSHA for investigation at the time of filing his application and payment of the required fees. Shipping charges shall be prepaid by the applicant.


(h) For a complete investigation leading to approval or certification the applicant shall furnish MSHA with the components necessary for inspection and testing. Expendable components shall be supplied by the applicant to permit continuous operation of the equipment while being tested. If special tools are necessary to assemble or disassemble any component for inspection or test, the applicant shall furnish them with the equipment to be tested.


(i) For investigation of a hose, the applicant shall furnish samples as follows:



Hose – a sample having a minimum length of 2 feet

(j) The applicant shall submit a sample caution statement (see Figure 3 in Appendix II) specifying the conditions for maintaining permissibility of the equipment.


(k) The applicant shall submit a factory-inspection form (see Figure 4 in Appendix II) used to maintain quality control at the place of manufacture or assembly to insure that component parts are made and assembled in strict accordance with the drawings and specifications covering a design submitted to MSHA for approval or certification.


(l) MSHA will accept an application for an approval, a letter of certification, or an acceptance for listing of a product that is manufactured in a country other than the United States provided: (1) All correspondence, specifications, lettering on drawings (metric-system dimensions acceptable), instructions, and related information are in English; and (2) all other requirements of this part are met the same as for a domestic applicant.


[33 FR 4660, Mar. 19, 1968, as amended at 43 FR 12314, Mar. 24, 1978; 47 FR 14696, Apr. 6, 1982; 57 FR 61223, Dec. 23, 1992; 60 FR 33723, June 29, 1995; 60 FR 35693, July 11, 1995; 68 FR 36419, June 17, 2003; 70 FR 46343, Aug. 9, 2005; 71 FR 28584, May 17, 2006; 73 FR 52211, Sept. 9, 2008; 73 FR 80611, Dec. 31, 2008]


§ 18.7 [Reserved]

§ 18.8 Date for conducting investigation and tests.

The date of receipt of an application will determine the order of precedence for investigation and testing. If an electrical machine component or accessory fails to meet any of the requirements, it shall lose its order of precedence. If an application is submitted to resume investigation and testing after correction of the cause of failure, it will be treated as a new application and the order of precedence for investigation and testing will be so determined.


§ 18.9 Conduct of investigations and tests.

(a) Prior to the issuance of an approval, certification, or acceptance of a hose, only MSHA personnel, representative(s) of the applicant, and such other person(s) as may be mutually agreed upon may observe any part of the investigation or tests. The MSHA will hold as confidential and will not disclose principles or patentable features; nor will it disclose to persons other than the applicant the results of tests, chemical analysis of materials or any details of the applicant’s drawings, specifications, instructions, and related material.


(b) Unless notified to the contrary by MSHA, the applicant shall provide assistance in disassembling parts for inspection, preparing parts for testing, and preparing equipment for return shipment. Explosion-proof enclosures shall be drilled and tapped for pipe connections in accordance with instructions supplied by MSHA.


(c) MSHA reserves the right to inspect a complete machine, component part, or accessory at a place other than the Bureau’s premises, such as the assembly plant or other location acceptable to MSHA, at the applicant’s expense.


(d) Applicants shall be responsible for their representatives present during tests and for observers admitted at their request and shall save the Government harmless in the event of damage to applicant’s property or injury to applicant’s representatives or to observers admitted at their request.


[33 FR 4660, Mar. 19, 1968; 33 FR 6345, Apr. 26, 1968, as amended at 57 FR 61223, Dec. 23, 1992; 73 FR 80612, Dec. 31, 2008]


§ 18.10 Notice of approval or disapproval.

(a) Upon completing investigation of a complete assembly of an electrical machine or accessory, MSHA will issue to the applicant either a written notice of approval or a written notice of disapproval, as the case may require. No informal notification of approval will be issued. If a notice of disapproval is issued, it will be accompanied by details of the defects, with recommendations for possible correction. MSHA will not disclose, except to the applicant, any information upon which a notice of disapproval has been issued.


(b) A formal notice of approval will be accompanied by a list of drawings, specifications, and related material, covering the details of design and construction of the equipment upon which the approval is based. Applicants shall keep exact duplicates of the drawings, specifications, and descriptions that relate to equipment for which an approval has been issued, and the drawings and specifications shall be adhered to exactly in production of the approved equipment.


(c) An applicant shall not advertise or otherwise represent his equipment as approved (permissible) until he has received MSHA’s formal notice of approval.


§ 18.11 Approval plate.

(a)(1) The notice of approval will be accompanied by a photograph of an approval plate, bearing the emblem of Mine Safety and Health Administration, the name of the complete assembly, the name of the applicant, and spaces for the approval number, serial number, and the type or model of machine.


(2) An extension of approval will not affect the original approval number except that the extension number shall be added to the original approval number on the approval plate. (Example: Original approval No. 2G-3000; seventh extension No. 2G-3000-7.)


(b) The applicant shall reproduce the design on a separate plate, which shall be attached in a suitable place, on each complete assembly to which it relates. The size, type, location, and method of attaching an approval plate are subject to MSHA’s concurrence. The method for affixing the approval plate shall not impair any explosion-proof feature of the equipment.


(c) The approval plate identifies as permissible the machine or accessory to which it is attached, and use of the approval plate obligates the applicant to whom the approval was issued to maintain in his plant the quality of each complete assembly and guarantees that the equipment is manufactured and assembled according to the drawings, specifications, and descriptions upon which the approval and subsequent extension(s) of approval were based.


(d) A completely assembled approved machine with an integral dust collector shall bear an approval plate indicating that the requirements of part 33 of this chapter (Bureau of Mines Schedule 25B), have been complied with. Approval numbers will be assigned under each part of such joint approvals.


[33 FR 4660, Mar. 19, 1968, as amended at 43 FR 12314, Mar. 24, 1978]


§ 18.12 Letter of certification.

(a) A letter of certification may be issued by MSHA for a component intended for incorporation in a complete machine or accessory for which an approval may be subsequently issued. A letter of certification will be issued to an applicant when a component has met all the applicable requirements of this part. Included in the letter of certification will be an assigned MSHA certification number that will identify the certified component.


(b) A letter of certification will be accompanied by a list of drawings, specifications, and related material covering the details of design and construction of a component upon which the letter of certification is based. Applicants shall keep exact duplicates of the drawings, specifications, and descriptions that relate to the component for which a letter of certification has been issued; and the drawings and specifications shall be adhered to exactly in production of the certified component.


(c) A component shall not be represented as certified until the applicant has received MSHA’s letter of certification for the component. Certified components are not to be represented as “approved” or “permissible” because such terms apply only to completely assembled machines or accessories.


§ 18.13 Certification plate.

Each certified component shall be identified by a certification plate attached to the component in a manner acceptable to MSHA. The method of attachment shall not impair any explosion-proof characteristics of the component. The plate shall be of serviceable material, acceptable, to MSHA, and shall contain the following:



Certified as complying with the applicable requirements of 30 CFR part ____.

Certification No.____.

The blank spaces shall be filled with appropriate designations. Inclusion of the information on a company name plate will be permitted provided the plate is made of material acceptable to MSHA.


§ 18.14 Identification of tested noncertified explosion-proof enclosures.

An enclosure that meets all applicable requirements of this part, but has not been certified by MSHA, shall be identified by a permanent marking on it in a conspicuous location. The design of such marking shall consist of capital letters USMSHA not less than
1/4 inch in height, enclosed in a circle not less than 1 inch in diameter.


[33 FR 4660, Mar. 19, 1968, as amended at 43 FR 12314, Mar. 24, 1978]


§ 18.15 Changes after approval or certification.

If an applicant desires to change any feature of approved equipment or a certified component, he shall first obtain MSHA’s concurrence pursuant to the following procedure:


(a)(1) Application shall be made as for an original approval or letter of certification requesting that the existing approval or certification be extended to cover the proposed changes and shall be accompanied by drawings, specifications, and related information, showing the changes in detail.


(2) Where the applicant for approval has used an independent laboratory under part 6 of this chapter to perform, in whole or in part, the necessary testing and evaluation for approval of changes to an approved or certified product under this part, the applicant must provide to MSHA as part of the approval application:


(i) Written evidence of the laboratory’s independence and current recognition by a laboratory accrediting organization;


(ii) Complete technical explanation of how the product complies with each requirement in the applicable MSHA product approval requirements;


(iii) Identification of components or features of the product that are critical to the safety of the product; and


(iv) All documentation, including drawings and specifications, as submitted to the independent laboratory by the applicant and as required by this part.


(b) The application will be examined by MSHA to determine whether inspection or testing will be required. Testing will be required if there is a possibility that the change(s) may adversely affect safety.


(c) If the change(s) meets the requirements of this part, a formal extension of approval or certification will be issued, accompanied by a list of new or revised drawings, specifications, and related information to be added to those already on file for the original approval or certification.


(d) Revisions in drawings or specifications that do not involve actual change in the explosion-proof features of equipment may be handled informally.


[43 FR 12313, Mar. 24, 1978, as amended at 52 FR 17514, May 8, 1987; 68 FR 36419, June 17, 2003]


§ 18.16 Withdrawal of approval, certification, or acceptance.

MSHA reserves the right to rescind, for cause, any approval, certification, acceptance, or extension thereof, issued under this part.


Subpart B – Construction and Design Requirements

§ 18.20 Quality of material, workmanship, and design.

(a) Electrically operated equipment intended for use in coal mines shall be rugged in construction and shall be designed to facilitate inspection and maintenance.


(b) MSHA will test only electrical equipment that in the opinion of its qualified representatives is constructed of suitable materials, is of good quality workmanship, based on sound engineering principles, and is safe for its intended use. Since all possible designs, circuits, arrangements, or combinations of components and materials cannot be foreseen, MSHA reserves the right to modify design, construction, and test requirements to obtain the same degree of protection as provided by the tests described in Subpart C of this part.


(c) Moving parts, such as rotating saws, gears, and chain drives, shall be guarded to prevent personal injury.


(d) Flange joints and lead entrances shall be accessible for field inspection, where practicable.


(e) An audible warning device shall be provided on each mobile machine that travels at a speed greater than 2.5 miles per hour.


(f) Brakes shall be provided for each wheel-mounted machine, unless design of the driving mechanism will preclude accidental movement of the machine when parked.


(g) A headlight and red light-reflecting material shall be provided on both front and rear of each mobile transportation unit that travels at a speed greater than 2.5 miles per hour. Red light-reflecting material should be provided on each end of other mobile machines.


§ 18.21 Machines equipped with powered dust collectors.

Powered dust collectors on machines submitted for approval shall meet the applicable requirements of Part 33 of this chapter (Bureau of Mines Schedule 25B), and shall bear the approval number assigned by MSHA.


§ 18.22 Boring-type machines equipped for auxiliary face ventilation.

Each boring-type continuous-mining machine that is submitted for approval shall be constructed with an unobstructed continuous space(s) of not less than 200 square inches total cross-sectional area on or within the machine to which flexible tubing may be attached to facilitate auxiliary face ventilation.


§ 18.23 Limitation of external surface temperatures.

The temperature of the external surfaces of mechanical or electrical components shall not exceed 150 °C. (302 °F.) under normal operating conditions.


§ 18.24 Electrical clearances.

Minimum clearances between uninsulated electrical conductor surfaces, or between uninsulated conductor surfaces and grounded metal surfaces, within the enclosure shall be as follows:


Minimum Clearances Between Uninsulated Surfaces

Phase-to-Phase Voltage (rms)
Clearances (inches)
Phase-to-Phase
Phase-to-Ground or Control Circuit
0 to 2500.250.25
251 to 6000.280.25
601 to 10000.610.25
1001 to 24001.40.6
2401 to 41603.01.4

[57 FR 61209, Dec. 23, 1992]


§ 18.25 Combustible gases from insulating material.

(a) Insulating materials that give off flammable or explosive gases when decomposed electrically shall not be used within enclosures where the materials are subjected to destructive electrical action.


(b) Parts coated or impregnated with insulating materials shall be heat-treated to remove any combustible solvent(s) before assembly in an explosion-proof enclosure. Air-drying insulating materials are excepted.


§ 18.26 Static electricity.

Nonmetallic rotating parts, such as belts and fans, shall be provided with a means to prevent an accumulation of static electricity.


§ 18.27 Gaskets.

A gasket(s) shall not be used between any two surfaces forming a flame-arresting path except as follows:


(a) A gasket of lead, elastomer, or equivalent will be acceptable provided the gasket does not interfere with an acceptable metal-to-metal joint.


(b) A lead gasket(s) or equivalent will be acceptable between glass and a hard metal to form all or a part of a flame-arresting path.


§ 18.28 Devices for pressure relief, ventilation, or drainage.

(a) Devices for installation on explosion-proof enclosures to relieve pressure, ventilate, or drain will be acceptable provided the length of the flame-arresting path and the clearances or size of holes in perforated metal will prevent discharge of flame in explosion tests.


(b) Devices for pressure relief, ventilation, or drainage shall be constructed of materials that resist corrosion and distortion, and be so designed that they can be cleaned readily. Provision shall be made for secure attachment of such devices.


(c) Devices for pressure relief, ventilation, or drainage will be acceptable for application only on enclosures with which they are explosion tested.


§ 18.29 Access openings and covers, including unused lead-entrance holes.

(a) Access openings in explosion-proof enclosures will be permitted only where necessary for maintenance of internal parts such as motor brushes and fuses.


(b) Covers for access openings shall meet the same requirements as any other part of an enclosure except that threaded covers shall be secured against loosening, preferably with screws having heads requiring a special tool. (See Figure 1 in Appendix II.)


(c) Holes in enclosures that are provided for lead entrances but which are not in use shall be closed with metal plugs secured by spot welding, brazing, or equivalent. (See Figure 10 in Appendix II.)


§ 18.30 Windows and lenses.

(a) MSHA may waive testing of materials for windows or lenses except headlight lenses. When tested, material for windows or lenses shall meet the test requirements prescribed in § 18.66 and shall be sealed in place or provided with flange joints in accordance with § 18.31.


(b) Windows or lenses shall be protected from mechanical damage by structural design, location, or guarding. Windows or lenses, other than headlight lenses, having an exposed area greater than 8 square inches, shall be provided with guarding or equivalent.


§ 18.31 Enclosures – joints and fastenings.

(a) Explosion-proof enclosures:


(1) Cast or welded enclosures shall be designed to withstand a minimum internal pressure of 150 pounds per square inch (gage). Castings shall be free from blowholes.


(2) Welded joints forming an enclosure shall have continuous gas-tight welds. All welds shall be made in accordance with American Welding Society standards.


(3) External rotating parts shall not be constructed of aluminum alloys containing more than 0.6 percent magnesium.


(4) MSHA reserves the right to require the applicant to conduct static-pressure tests on each enclosure when MSHA determines that the particular design will not permit complete visual inspection or when the joint(s) forming an enclosure is welded on one side only (see § 18.67).


(5) Threaded covers and mating parts shall be designed with Class 1A and 1B (coarse, loose-fitting) threads. The flame-arresting path of threaded joints shall conform to the requirements of paragraph (a)(6) of this section.


(6) Enclosure requirements shall be based on the internal volumes of the empty enclosure. The internal volume is the volume remaining after deducting the volume of any part that is essential in maintaining the explosion-proof integrity of the enclosure or necessary for the operation. Essential parts include the parts that constitute the flame-arresting path and those necessary to secure parts that constitute a flame-arresting path. Enclosures shall meet the following requirements:


Explosion-Proof Requirements Based on Volume


Volume of empty enclosure
Less than 45 cu. in.
45 to 124 cu. in. inclusive
More than 124 cu. in.
Minimum thickness of material for walls
1

1/8

3/16

1/4
Minimum thickness of material for flanges and covers
2
1/4

3
3/8

3
1/2
Minimum width of joint; all in one plane
4

1/2

3/4
1″
Maximum clearance; joint all in one plane0.002″0.003″0.004″
Minimum width of joint, portions of which are in different planes; cylinders or equivalent
4 5

3/8

5/8

3/4
Maximum clearances; joint in two or more planes, cylinders or equivalent:
(a) Portion perpendicular to plane
6
0.008″0.008″0.008″
(b) Plane portion0.006″0.006″0.006″
Maximum bolt
7 8 spacing; joints all in one plane
(
16)
(
16)
(
16)
Maximum bolt spacing; joints, portions of which are in different planes(
9)
(
9)
(
9)
Minimum diameter of bolt (without regard to type of joint)
1/4

1/4

3/8
Minimum thread engagement
10

1/4

1/4

3/8
Maximum diametrical clearance between bolt body and unthreaded holes through which it passes
8 11 12

1/64

1/32

1/16
Minimum distance from interior of enclosure to the edge of a bolt hole:
8 13
Joint – minimum width 1″
14
7/16
Joint – less than 1″ wide
1/8

3/16
Cylindrical joints
Shaft centered by ball or roller bearings:
Minimum length of flame-arresting path
1/2

3/4
1″
Maximum diametrical clearance0.020″0.025″0.030″
Other cylindrical joints:
15
Minimum length of flame-arresting path
1/2

3/4
1″
Maximum diametrical clearance0.006″0.008″0.010″


1 This is the minimal nominal dimension when applied to standard steel plate.


2
1/32 inch less is allowable for machining rolled plate.


3
1/16 inch less is allowable for machining rolled plate.


4 The widths of any grooves, such as grooves for holding oil seals or O-rings, shall be deducted in measuring the widths of flame-arresting paths.


5 If only two planes are involved, neither portion of a joint shall be less than
1/8 inch wide, unless the wider portion conforms to the same requirements as those for a joint that is all in one plane. If more than two planes are involved (as in labyrinths or tongue-and-groove joints) the combined lengths of those portions having prescribed clearances are considered.


6 The allowable diametrical clearance is 0.008 inch when the portion perpendicular to the plane portion is
1/4 inch or greater in length. If the perpendicular portion is more than
1/8 inch but less than
1/4 inch wide, the diametrical clearance shall not exceed 0.006 inch.


7 Where the term “bolt” is used, it refers to a machine bolt or a cap screw, and for either of these studs may be substituted provided the studs, bottom in blind holes, are completely welded in place, or the bottom of the hole is closed with a plug secured by weld or braze. Bolts shall be provided at all corners.


8 The requirements as to diametrical clearance around the bolt and minimum distance from the bolt hole to the inside of the explosion-proof enclosure apply to steel dowel pins. In addition, when such pins are used, the spacing between centers of the bolts on either side of the pin shall not exceed 5 inches.


9 Adequacy of bolt spacing will be judged on the basis of size and configuration of the enclosure, strength of materials, and explosion test results.


10 In general, minimum thread engagement shall be equal to or greater than the diameter of the bolt specified.


11 Threaded holes for fastening bolts shall be machined to remove burrs or projections that affect planarity of a surface forming a flame-arresting path.


12 This maximum clearance applies only when the bolt is located within the flamepath.


13 The edge of the bolt hole shall include the edge of any machining done to the bolt hole, such as chamfering.


14 Less than
7/16″ (
1/4″ minimum) will be acceptable provided the diametrical clearance for fastening bolts does not exceed
1/32″.


15 Shafts or operating rods through journal bearings shall be at least
1/4″ in diameter. The length of fit shall not be reduced when a push button is depressed. Operating rods shall have a shoulder or head on the portion inside the enclosure. Essential parts riveted or bolted to the inside portion are acceptable in lieu of a head or shoulder, but cotter pins and similar devices shall not be used.


16 6″ with a minimum of 4 bolts.


(7) O-rings, if used in a flame-arresting path, shall meet the following:


(i) When the flame-arresting path is in one plane, the o-ring shall be located at least one-half the acceptable flame-arresting path length specified in paragraph (a)(6) of this section within the outside edge of the path (see figure J-2 in the appendix to subpart J of part 7 of this chapter).


(ii) When the flame-arresting path is one of the plane-cylindrical type (step joint), the o-ring shall be located at least
1/2 inch within the outer edge of the plane portion (see figure J-3 in the appendix to subpart J of part 7 of this chapter), or at the junction of the plane and cylindrical portion of the joint (see figure J-4 in the appendix to subpart J of part 7 of this chapter); or in the cylindrical portion (see figure J-5 in the appendix to subpart J of part 7 of this chapter).


(8) Mating parts comprising a pressed fit shall result in a minimum interference of 0.001 inch between the parts. The minimum length of the pressed fit shall be equal to the minimum thickness requirement of paragraph (a)(6) of this section for the material in which the fit is made.


(b) Enclosures for potted components: Enclosures shall be rugged and constructed with materials having 75 percent, or greater, of the thickness and flange width specified in paragraph (a) of this section. These enclosures shall be provided with means for attaching hose conduit, unless energy carried by the cable is intrinsically safe.


(c) No assembly will be approved that requires the opening of an explosion-proof enclosure to operate a switch, rheostat, or other device during normal operation of a machine.


[33 FR 4660, Mar. 19, 1968, as amended at 57 FR 61209, Dec. 23, 1992]


§ 18.32 Fastenings – additional requirements.

(a) Bolts, screws, or studs shall be used for fastening adjoining parts to prevent the escape of flame from an enclosure. Hinge pins or clamps will be acceptable for this purpose provided MSHA determines them to be equally effective.


(b) Lockwashers shall be provided for all bolts, screws, and studs that secure parts of explosion-proof enclosures. Special fastenings designed to prevent loosening will be acceptable in lieu of lockwashers, provided MSHA determines them to be equally effective.


(c) Fastenings shall be as uniform in size as practicable to preclude improper assembly.


(d) Holes for fastenings shall not penetrate to the interior of an explosion-proof enclosure, except as provided in paragraph (a)(9) of § 18.34, and shall be threaded to insure that a specified bolt or screw will not bottom even if its lockwasher is omitted.


(e) A minimum of
1/8-inch of stock shall be left at the center of the bottom of each hole drilled for fastenings.


(f) Fastenings used for joints on explosion-proof enclosures shall not be used for attaching nonessential parts or for making electrical connections.


(g) The acceptable sizes for and spacings of fastenings shall be determined by the size of the enclosure, as indicated in § 18.31.


(h) MSHA reserves the right to conduct explosion tests with standard bolts, nuts, cap screws, or studs substituted for any special high-tensile strength fastening(s) specified by the applicant.


(i) Coil-thread inserts, if used in holes for fastenings, shall meet the following:


(1) The inserts shall have internal screw threads.


(2) The holes for the inserts shall be drilled and tapped consistent with the insert manufacturer’s specifications.


(3) The inserts shall be installed consistent with the insert manufacturer’s specifications.


(4) The insert shall be of sufficient length to ensure the minimum thread engagement of fastening specified in § 18.31(a)(6) of this part.


[33 FR 4660, Mar. 19, 1968, as amended at 57 FR 61210, Dec. 23, 1992]


§ 18.33 Finish of surface joints.

Flat surfaces between bolt holes that form any part of a flame-arresting path shall be plane to within a maximum deviation of one-half the maximum clearance specified in § 18.31(a)(6). All metal surfaces forming a flame-arresting path shall be finished during the manufacturing process to not more than 250 microinches. A thin film of nonhardening preparation to inhibit rusting may be applied to these finished metal surfaces as long as the final surface can be readily wiped free of any foreign materials.


[57 FR 61210, Dec. 23, 1992]


§ 18.34 Motors.

Explosion-proof electric motor assemblies intended for use in approved equipment in underground mines that are specifically addressed in part 7 of this chapter shall be approved under part 7 of this chapter after February 22, 1996. Those motor assemblies not specifically addressed under part 7 of this chapter shall be accepted or certified under this part.


(a) General. (1) Motors shall have explosion-proof enclosures.


(2) Motors submitted to MSHA for test shall be equipped with unshielded bearings regardless of whether that type of bearing is specified.


(3) MSHA reserves the right to test motors with the maximum clearance specified between the shaft and the mating part which forms the required flame-arresting path. Also reserved is the right to remachine these parts, at the applicant’s expense, to specified dimensions to provide the maximum clearance.



Note:

For example, a shaft with a diameter greater than 2 inches at the flame-arresting portion might require such machining.


(4) Ball and roller bearings and oil seals will not be acceptable as flame-arresting paths; therefore, a separate path shall be provided between the shaft and another part, preferably inby the bearing. The length and clearances of such flame-arresting path shall conform to the requirements of § 18.31.


(5) Labyrinths or other arrangements that provide change(s) in direction of escaping gases will be acceptable but the use of small detachable pieces shall not be permitted unless structurally unavoidable. The lengths of flame-arresting path(s) and clearance(s) shall conform to the requirements of § 18.31.


(6) Oil seals shall be removed from motors prior to submission for explosion tests.



Note:

Oil seals will be removed from motors prior to explosion tests and therefore may be omitted from motors submitted for investigation.


(7) Openings for filling and draining bearing lubricants shall be so located as to prevent escape of flame through them.


(8) An outer bearing cap will not be considered as forming any part of a flame-arresting path unless the cap is used as a bearing cartridge.



Note:

The outer bearing cap will be omitted during explosion tests unless it houses the bearing.


(9) If unavoidable, holes may be made through motor casings for bolts, studs, or screws to hold essential parts such as pole pieces, brush rigging, and bearing cartridges. Such parts shall be attached to the casing by at least two fastenings. The threaded holes in these parts shall be blind, unless the fastenings are inserted from the inside, in which case the fastenings shall not be accessible with the armature of the motor in place.


(b) Direct-current motors. For direct-current motors with narrow interpoles, the distance from the edge of the pole piece to any bolt hole in the frame shall be not less than
1/8 inch. If the distance is
1/8 to
1/4 inch, the diametrical clearance for the pole bolt shall not exceed
1/64 inch for not less than
1/2 inch through the frame. Furthermore, the pole piece shall have the same radius as the inner surface of the frame. Pole pieces may be shimmed as necessary.


(c) Alternating-current motors. Stator laminations that form a part of an explosion-proof enclosure will be acceptable provided: (1) The laminations and their end rings are fastened together under pressure; (2) the joint between the end rings and the laminations is not less than
1/4 inch, but preferably as close to 1 inch as possible; and (3) it shall be impossible to insert a 0.0015-inch thickness gage to a depth exceeding
1/8 inch between adjacent laminations or between end rings and laminations.


(d) Small motors (alternating- and direct-current). Motors having internal free volume not exceeding 350 cubic inches and joints not exceeding 32 inches in outer circumference will be acceptable for investigation if provided with rabbet joints between the stator frame and the end bracket having the following dimensions:


Dimensions of Rabbet Joints – Inches

Minimum total width
Min. width of clamped radial

portion
Max. clearance of radial portion
Max.

diametrical clearance at axial portion

3/8

3/64
0.00150.003

1/2

3/64
.002.003

1/2

3/32
.002.004

[33 FR 4660, Mar. 19, 1968, as amended at 57 FR 61210, Dec. 23, 1992]


§ 18.35 Portable (trailing) cables and cords.

(a) Portable cables and cords used to conduct electrical energy to face equipment shall conform to the following:


(1) Have each conductor of a current-carrying capacity consistent with the Insulated Power Cable Engineers Association (IPCEA) standards. (See Tables 1 and 2 in Appendix I.)


(2) Have current-carrying conductors not smaller than No. 14 (AWG). Cords with sizes 14 to 10 (AWG) conductors shall be constructed with heavy jackets, the diameters of which are given in Table 6 in Appendix I.


(3) Be accepted as flame resistant under this part or approved under subpart K of part 7 of this chapter.


(4) Have short-circuit protection at the outby (circuit-connecting) end of ungrounded conductors. (See Table 8 in Appendix I.) The fuse rating or trip setting shall be included in the assembler’s specifications.


(5) Ordinarily the length of a portable (trailing) cable shall not exceed 500 feet. Where the method of mining requires the length of a portable (trailing) cable to be more than 500 feet, such length of cable shall be permitted only under the following prescribed conditions:


(i) The lengths of portable (trailing) cables shall not exceed those specified in Table 9, Appendix I, titled “Specifications for Portable Cables Longer Than 500 Feet.”


(ii) Short-circuit protection shall be provided by a protective device with an instantaneous trip setting as near as practicable to the maximum starting-current-inrush value, but the setting shall not exceed the trip value specified in MSHA approval for the equipment for which the portable (trailing) cable furnishes electric power.


(6) Have nominal outside dimensions consistent with IPCEA standards. (See Tables 4, 5, 6, and 7 in Appendix I.)


(7) Have conductors of No. 4 (AWG) minimum for direct-current mobile haulage units or No. 6 (AWG) minimum for alternating-current mobile haulage units.


(8) Have not more than five well-made temporary splices in a single length of portable cable.


(b) Sectionalized portable cables will be acceptable provided the connectors used inby the last open crosscut in a gassy mine meet the requirements of § 18.41.


(c) A portable cable having conductors smaller than No. 6 (AWG), when used with a trolley tap and a rail clamp, shall have well insulated single conductors not smaller than No. 6 (AWG) spliced to the outby end of each conductor. All splices shall be made in a workmanlike manner to insure good electrical conductivity, insulation, and mechanical strength.


(d) Suitable provisions shall be made to facilitate disconnection of portable cable quickly and conveniently for replacement.


[33 FR 4660, Mar. 19, 1968; 33 FR 6343, Apr. 26, 1968, as amended at 57 FR 61223, Dec. 23, 1992]


§ 18.36 Cables between machine components.

(a) Cables between machine components shall have: (1) Adequate current-carrying capacity for the loads involved, (2) short-circuit protection, (3) insulation compatible with the impressed voltage, and (4) flame-resistant properties unless totally enclosed within a flame-resistant hose conduit or other flame-resistant material.


(b) Cables between machine components shall be: (1) Clamped in place to prevent undue movement, (2) protected from mechanical damage by position, flame-resistant hose conduit, metal tubing, or troughs (flexible or threaded rigid metal conduit will not be acceptable), (3) isolated from hydraulic lines, and (4) protected from abrasion by removing all sharp edges which they might contact.


(c) Cables (cords) for remote-control circuits extending from permissible equipment will be exempted from the requirements of conduit enclosure provided the total electrical energy carried is intrinsically safe or that the cables are constructed with heavy jackets, the sizes of which are stated in Table 6 of Appendix I. Cables (cords) provided with hose-conduit protection shall have a tensile strength not less than No. 16 (AWG) three-conductor, type SO cord. (Reference: 7.7.7 IPCEA Pub. No. S-19-81, Fourth Edition.) Cables (cords) constructed with heavy jackets shall consist of conductors not smaller than No. 14 (AWG) regardless of the number of conductors.


§ 18.37 Lead entrances.

(a) Insulated cable(s), which must extend through an outside wall of an explosion-proof enclosure, shall pass through a stuffing-box lead entrance. All sharp edges that might damage insulation shall be removed from stuffing boxes and packing nuts.


(b) Stuffing boxes shall be so designed, and the amount of packing used shall be such, that with the packing properly compressed, the gland nut still has a clearance distance of
1/8 inch or more to travel without meeting interference by parts other than packing. In addition, the gland nut shall have a minimum of three effective threads engaged. (See figures 8, 9 and 10 in appendix II.)


(c) Packing nuts and stuffing boxes shall be secured against loosening.


(d) Compressed packing material shall be in contact with the cable jacket for a length of not less than
1/2 inch.


(e) Special requirements for glands in which asbestos-packing material is specified are:


(1) Asbestos-packing material shall be untreated, not less than
3/16-inch diameter if round, or not less than
3/16 by
3/16 inch if square. The width of the space for packing material shall not exceed by more than 50 percent the diameter or width of the uncompressed packing material.


(2) The allowable diametrical clearance between the cable and the holes in the stuffing box and packing nut shall not exceed 75 percent of the nominal diameter or width of the packing material.


(f) Special requirements for glands in which a compressible material (example – synthetic elastomers) other than asbestos is specified, are:


(1) The packing material shall be flame resistant.


(2) The radial clearance between the cable jacket and the nominal inside diameter of the packing material shall not exceed
1/32-inch, based on the nominal specified diameter of the cable.


(3) The radial clearance between the nominal outside diameter of the packing material and the inside wall of the stuffing box (that portion into which the packing material fits) shall not exceed
1/32-inch.


[33 FR 4660, Mar. 19, 1968, as amended at 57 FR 61210, Dec. 23, 1992]


§ 18.38 Leads through common walls.

(a) Insulated studs will be acceptable for use in a common wall between two explosion-proof enclosures.


(b) When insulated wires or cables are extended through a common wall between two explosion-proof enclosures in insulating bushings, such bushings shall be not less than 1-inch long and the diametrical clearance between the wire or cable insulation and the holes in the bushings shall not exceed
1/16-inch (based on the nominal specified diameter of the cable). The insulating bushings shall be secured in the metal wall.


(c) Insulated wires or cables conducted from one explosion-proof enclosure to another through conduit, tubing, piping, or other solid-wall passageways will be acceptable provided one end of the passageway is plugged, thus isolating one enclosure from the other. Glands of secured bushings with close-fitting holes through which the wires or cables are conducted will be acceptable for plugging. The tubing or duct specified for the passageway shall be brazed or welded into the walls of both explosion-proof enclosures with continuous gas-tight welds.


(d) If wires and cables are taken through openings closed with sealing compounds, the design of the opening and characteristics of the compounds shall be such as to hold the sealing material in place without tendency of the material to crack or flow out of its place. The material also must withstand explosion tests without cracking or loosening.


(e) Openings through common walls between explosion-proof enclosures not provided with bushings or sealing compound, shall be large enough to prevent pressure piling.


§ 18.39 Hose conduit.

Hose conduit shall be provided for mechanical protection of all machine cables that are exposed to damage. Hose conduit shall be flame resistant and have a minimum wall thickness of
3/16 inch. The flame resistance of hose conduit will be determined in accordance with the requirements of § 18.65.


§ 18.40 Cable clamps and grips.

Insulated clamps shall be provided for all portable (trailing) cables to prevent strain on the cable terminals of a machine. Also insulated clamps shall be provided to prevent strain on both ends of each cable or cord leading from a machine to a detached or separately mounted component. Cable grips anchored to the cable may be used in lieu of insulated strain clamps. Supporting clamps for cables used for wiring around machines shall be provided in a manner acceptable to MSHA.


§ 18.41 Plug and receptacle-type connectors.

(a) Plug and receptacle-type connectors for use inby the last open crosscut in a gassy mine shall be so designed that insertion or withdrawal of a plug cannot cause incendive arcing or sparking. Also, connectors shall be so designed that no live terminals, except as hereinafter provided, are exposed upon withdrawal of a plug. The following types will be acceptable:


(1) Connectors in which the mating or separation of the male and female electrodes is accomplished within an explosion-proof enclosure.


(2) Connectors that are mechanically or electrically interlocked with an automatic circuit-interrupting device.


(i) Mechanically interlocked connectors. If a mechanical interlock is provided the design shall be such that the plug cannot be withdrawn before the circuit has been interrupted and the circuit cannot be established with the plug partially withdrawn.


(ii) Electrically interlocked connectors. If an electrical interlock is provided, the total load shall be removed before the plug can be withdrawn and the electrical energy in the interlocking pilot circuit shall be intrinsically safe, unless the pilot circuit is opened within an explosion-proof enclosure.


(3) Single-pole connectors for individual conductors of a circuit used at terminal points shall be so designed that all plugs must be completely inserted before the control circuit of the machine can be energized.


(b) Plug and receptacle-type connectors used for sectionalizing the cables outby the last open crosscut in a gassy mine need not be explosion-proof or electrically interlocked provided such connectors are designed and constructed to prevent accidental separation.


(c) Conductors shall be securely attached to the electrodes in a plug or receptacle and the connections shall be totally enclosed.


(d) Molded-elastomer connectors will be acceptable provided:


(1) Any free space within the plug or receptacle is isolated from the exterior of the plug.


(2) Joints between the elastomer and metal parts are not less than 1 inch wide and the elastomer is either bonded to or fits tightly with metal parts.


(e) The contacts of all line-side connectors shall be shielded or recessed adequately.


(f) For a mobile battery-powered machine, a plug and receptacle-type connector will be acceptable in lieu of an interlock provided:


(1) The plug is padlocked to the receptacle and is held in place by a threaded ring or equivalent mechanical fastening in addition to a padlock. A connector within a padlocked enclosure will be acceptable; or,


(2) The plug is held in place by a threaded ring or equivalent mechanical fastening, in addition to the use of a device that is captive and requires a special tool to disengage and allow for the separation of the connector. All connectors using this means of compliance shall have a clearly visible warning tag that states: “DO NOT DISENGAGE UNDER LOAD,” or an equivalent statement; or,


(3) The plug is held in place by a spring-loaded or other locking device, that maintains constant pressure against a threaded ring or equivalent mechanical fastening, to secure the plug from accidental separation. All connectors using this means of compliance shall have a clearly visible warning tag that states: “DO NOT DISENGAGE UNDER LOAD,” or an equivalent statement.


[33 FR 4660, Mar. 19, 1968, as amended at 68 FR 37082, June 23, 2003]


§ 18.42 Explosion-proof distribution boxes.

(a) A cable passing through an outside wall(s) of a distribution box shall be conducted either through a packing gland or an interlocked plug and receptacle.


(b) Short-circuit protection shall be provided for each branch circuit connected to a distribution box. The current-carrying capacity of the specified connector shall be compatible with the automatic circuit-interrupting device.


(c) Each branch receptacle shall be plainly and permanently marked to indicate its current-carrying capacity and each receptacle shall be such that it will accommodate only an appropriate plug.


(d) Provision shall be made to relieve mechanical strain on all connectors to distribution boxes.


§ 18.43 Explosion-proof splice boxes.

Internal connections shall be rigidly held and adequately insulated. Strain clamps shall be provided for all cables entering a splice box.


§ 18.44 Non-intrinsically safe battery-powered equipment.

(a) Battery-powered equipment shall use battery assemblies approved under Part 7 of this chapter, or battery assemblies accepted or certified under this part prior to August 22, 1989.


(b) Battery box covers shall be secured in a closed position.


(c) Each wire or cable leaving a battery box on storage battery-operated equipment shall have short-circuit protection in an explosion-proof enclosure located as close as practicable to the battery terminals. A short-circuit protection device installed within a nearby explosion-proof enclosure will be acceptable. In no case shall the exposed portion of the cable from the battery box to the enclosure exceed 36 inches in length. Each wire or cable shall be protected from damage.


[53 FR 23500, June 22, 1988]


§ 18.45 Cable reels.

(a) A self-propelled machine, that receives electrical energy through a portable cable and is designed to travel at speeds exceeding 2.5 miles per hour, shall have a mechanically, hydraulically, or electrically driven reel upon which to wind the portable cable.


(b) The enclosure for moving contacts or slip rings of a cable reel shall be explosion-proof.


(c) Cable-reel bearings shall not constitute an integral part of a circuit for transmitting electrical energy.


(d) Cable reels for shuttle cars and locomotives shall maintain positive tension on the portable cable during reeling and unreeling. Such tension shall only be high enough to prevent a machine from running over its own cable(s).


(e) Cable reels and spooling devices shall be insulated with flame-resistant material.


(f) The maximum speed of travel of a machine when receiving power through a portable (trailing) cable shall not exceed 6 miles per hour.


(g) Diameters of cable reel drums and sheaves should be large enough to prevent undue bending strain on cables.


§ 18.46 Headlights.

(a) Headlights shall be constructed as explosion-proof enclosures.


(b) Headlights shall be mounted to provide illumination where it will be most effective. They shall be protected from damage by guarding or location.


(c) Lenses for headlights shall be glass or other suitable material with physical characteristics equivalent to
1/2-inch thick tempered glass, such as “Pyrex.” Lenses shall meet the requirements of the tests prescribed in § 18.66.


(d) Lenses permanently fixed in a ring with lead, epoxy, or equivalent will be acceptable provided only lens assemblies meeting the original manufacturer’s specifications are used as replacements.


(e) If a single lead gasket is used, the contact surface of the opposite side of the lens shall be plane within a maximum deviation of 0.002 inch.


§ 18.47 Voltage limitation.

(a) A tool or switch held in the operator’s hand or supported against his body will not be approved with a nameplate rating exceeding 300 volts direct current or alternating current.


(b) A battery-powered machine shall not have a nameplate rating exceeding 240 volts, nominal (120 lead-acid cells or equivalent).


(c) Other direct-current machines shall not have a nameplate rating exceeding 550 volts.


(d) An alternating-current machine shall not have a nameplate rating exceeding 660 volts, except that a machine may have a nameplate rating greater than 660 volts but not exceeding 4,160 volts when the following conditions are complied with:


(1) Adequate clearances and insulation for the particular voltage(s) are provided in the design and construction of the equipment, its wiring, and accessories.


(2) A continuously monitored, failsafe grounding system is provided that will maintain the frame of the equipment and the frames of all accessory equipment at ground potential. Also, the equipment, including its controls and portable (trailing) cable, will be deenergized automatically upon the occurrence of an incipient ground fault. The ground-fault-tripping current shall be limited by grounding resistor(s) to that necessary for dependable relaying. The maximum ground-fault-tripping current shall not exceed 25 amperes.


(3) All high voltage switch gear and control for equipment having a nameplate rating exceeding 1,000 volts are located remotely and operated by remote control at the main equipment. Potential for remote control shall not exceed 120 volts.


(4) Portable (trailing) cable for equipment with nameplate ratings from 661 volts through 1,000 volts shall include grounding conductors, a ground check conductor, and grounded metallic shields around each power conductor or a grounded metallic shield over the assembly; except that on machines employing cable reels, cables without shields may be used if the insulation is rated 2,000 volts or more.


(5) Portable (trailing) cable for equipment with nameplate ratings from 1,001 volts through 4,160 volts shall include grounding conductors, a ground check conductor, and grounded metallic shields around each power conductor.


(6) MSHA reserves the right to require additional safeguards for high-voltage equipment, or modify the requirements to recognize improved technology.


§ 18.48 Circuit-interrupting devices.

(a) Each machine shall be equipped with a circuit-interrupting device by means of which all power conductors can be deenergized at the machine. A manually operated controller will not be acceptable as a service switch.


(b) When impracticable to mount the main-circuit-interrupting device on a machine, a remote enclosure will be acceptable. When contacts are used as a main-circuit-interrupting device, a means for opening the circuit shall be provided at the machine and at the remote contactors.


(c) Separate two-pole switches shall be provided to deenergize power conductors for headlights or floodlights.


(d) Each handheld tool shall be provided with a two-pole switch of the “dead-man-control” type that must be held closed by hand and will open when hand pressure is released.


(e) A machine designed to operate from both trolley wire and portable cable shall be provided with a transfer switch, or equivalent, which prevents energizing one from the other. Such a switch shall be designed to prevent electrical connection to the machine frame when the cable is energized.


(f) Belt conveyors shall be equipped with control switches to automatically stop the driving motor in the event the belt is stopped, or abnormally slowed down.



Note:

Short transfer-type conveyors will be exempted from this requirement when attended.


§ 18.49 Connection boxes on machines.

Connection boxes used to facilitate replacement of cables or machine components shall be explosion-proof. Portable-cable terminals on cable reels need not be in explosion-proof enclosures provided that connections are well made, adequately insulated, protected from damage by location, and securely clamped to prevent mechanical strain on the connections.


§ 18.50 Protection against external arcs and sparks.

Provision shall be made for maintaining the frames of all off-track machines and the enclosures of related detached components at safe voltages by using one or a combination of the following:


(a) A separate conductor(s) in the portable cable in addition to the power conductors by which the machine frame can be connected to an acceptable grounding medium, and a separate conductor in all cables connecting related components not on a common chassis. The cross-sectional area of the additional conductor(s) shall not be less than 50 percent of that of one power conductor unless a ground-fault tripping relay is used, in which case the minimum size may be No. 8 (AWG). Cables smaller than No. 6 (AWG) shall have an additional conductor(s) of the same size as one power conductor.


(b) A means of actuating a circuit-interrupting device, preferably at the outby end of the portable cable.



Note:

The frame to ground potential shall not exceed 40 volts.


(c) A device(s) such as a diode(s) of adequate peak inverse voltage rating and current-carrying capacity to conduct possible fault current through the grounded power conductor. Diode installations shall include: (1) An overcurrent device in series with the diode, the contacts of which are in the machine’s control circuit; and (2) a blocking diode in the control circuit to prevent operation of the machine with the polarity reversed.


§ 18.51 Electrical protection of circuits and equipment.

(a) An automatic circuit-interrupting device(s) shall be used to protect each ungrounded conductor of a branch circuit at the junction with the main circuit when the branch-circuit conductor(s) has a current carrying capacity less than 50 percent of the main circuit conductor(s), unless the protective device(s) in the main circuit will also provide adequate protection for the branch circuit. The setting of each device shall be specified. For headlight and control circuits, each conductor shall be protected by a fuse or equivalent. Any circuit that is entirely contained in an explosion-proof enclosure shall be exempt from these requirements.


(b) Each motor shall be protected by an automatic overcurrent device. One protective device will be acceptable when two motors of the same rating operate simultaneously and perform virtually the same duty.


(1) If the overcurrent-protective device in a direct-current circuit does not open both lines, particular attention shall be given to marking the polarity at the terminals or otherwise preventing the possibility of reversing connections which would result in changing the circuit interrupter to the grounded line.


(2) Three-phase alternating-current motors shall have an overcurrent-protective device in at least two phases such that actuation of a device in one phase will cause the opening of all three phases.


(c) Circuit-interrupting devices shall be so designed that they can be reset without opening the compartment in which they are enclosed.


(d) All magnetic circuit-interrupting devices shall be mounted in a manner to preclude the possibility of their closing by gravity.


§ 18.52 Renewal of fuses.

Enclosure covers that provide access to fuses, other than headlight, control-circuit, and handheld-tool fuses, shall be interlocked with a circuit-interrupting device. Fuses shall be inserted on the load side of the circuit interrupter.


§ 18.53 High-voltage longwall mining systems.

(a) In each high-voltage motor-starter enclosure, with the exception of a controller on a high-voltage shearer, the disconnect device compartment, control/communications compartment, and motor contactor compartment must be separated by barriers or partitions to prevent exposure of personnel to energized high-voltage conductors or parts. In each motor-starter enclosure on a high-voltage shearer, the high-voltage components must be separated from lower voltage components by barriers or partitions to prevent exposure of personnel to energized high-voltage conductors or parts. Barriers or partitions must be constructed of grounded metal or nonconductive insulating board.


(b) Each cover of a compartment in the high-voltage motor-starter enclosure containing high-voltage components must be equipped with at least two interlock switches arranged to automatically deenergize the high-voltage components within that compartment when the cover is removed.


(c) Circuit-interrupting devices must be designed and installed to prevent automatic reclosure.


(d) Transformers with high-voltage primary windings that supply control voltages must incorporate grounded electrostatic (Faraday) shielding between the primary and secondary windings. The shielding must be connected to equipment ground by a minimum No. 12 AWG grounding conductor. The secondary nominal voltage must not exceed 120 volts, line to line.


(e) Test circuits must be provided for checking the condition of ground-wire monitors and ground-fault protection without exposing personnel to energized circuits. Each ground-test circuit must inject a primary current of 50 percent or less of the current rating of the grounding resistor through the current transformer and cause each corresponding circuit-interrupting device to open.


(f) Each motor-starter enclosure, with the exception of a controller on a high-voltage shearer, must be equipped with a disconnect device installed to deenergize all high-voltage power conductors extending from the enclosure when the device is in the “open” position.


(1) When multiple disconnect devices located in the same enclosure are used to satisfy the above requirement they must be mechanically connected to provide simultaneous operation by one handle.


(2) The disconnect device must be rated for the maximum phase-to-phase voltage and the full-load current of the circuit in which it is located, and installed so that –


(i) Visual observation determines that the contacts are open without removing any cover;


(ii) The load-side power conductors are grounded when the device is in the “open” position;


(iii) The device can be locked in the “open” position;


(iv) When located in an explosion-proof enclosure, the device must be designed and installed to cause the current to be interrupted automatically prior to the opening of the contacts; and


(v) When located in a non-explosion-proof enclosure, the device must be designed and installed to cause the current to be interrupted automatically prior to the opening of the contacts, or the device must be capable of interrupting the full-load current of the circuit.


(g) Control circuits for the high-voltage motor starters must be interlocked with the disconnect device so that –


(1) The control circuit can be operated with an auxiliary switch in the “test” position only when the disconnect device is in the open and grounded position; and


(2) The control circuit can be operated with the auxiliary switch in the “normal” position only when the disconnect switch is in the closed position.


(h) A study to determine the minimum available fault current must be submitted to MSHA to ensure adequate protection for the length and conductor size of the longwall motor, shearer and trailing cables.


(i) Longwall motor and shearer cables with nominal voltages greater than 660 volts must be made of a shielded construction with a grounded metallic shield around each power conductor.


(j) High-voltage motor and shearer circuits must be provided with instantaneous ground-fault protection of not more than 0.125-amperes. Current transformers used for this protection must be of the single-window type and must be installed to encircle all three phase conductors.


(k) Safeguards against corona must be provided on all 4,160 voltage circuits in explosion-proof enclosures.


(l) The maximum pressure rise within an explosion-proof enclosure containing high-voltage switchgear must be limited to 0.83 times the design pressure.


(m) High-voltage electrical components located in high-voltage explosion-proof enclosures must not be coplanar with a single plane flame-arresting path.


(n) Rigid insulation between high-voltage terminals (Phase-to-Phase or Phase-to-Ground) must be designed with creepage distances in accordance with the following table:


Minimum Creepage Distances

Phase to phase voltage
Points of

measure
Minimum creepage distances (inches) for comparative tracking index (CTI) range
1
CTI≥500
380≤CTI175≤CTICTI
2,4000-0

0-G
1.50

1.00
1.95

1.25
2.40

1.55
2.90

1.85
4,1600-0

0-G
2.40

1.50
3.15

1.95
3.90

2.40
4.65

2.90


1 Assumes that all insulation is rated for the applied voltage or higher.


(o) Explosion-proof motor-starter enclosures must be designed to establish the minimum free distance (MFD) between the wall or cover of the enclosure and uninsulated electrical conductors inside the enclosure in accordance with the following table:


High-Voltage Minimum Free Distances (MFD)

Wall/cover thickness (in)
Steel MFD (in)
Aluminum MFD (in)
A
1
B
2
C
3
A
B
C

1/4
2.84.35.8
4 NA

4 NA

4 NA

3/8
1.82.33.98.612.818.1

1/2
* 1.22.02.76.59.813.0

5/8
* 0.91.52.15.17.710.4

3/4
* 0.6* 1.11.64.16.38.6
1(*)* 0.6* 1.02.94.56.2

Note: * The minimum electrical clearances must still be maintained.


1 Column A specifies the MFD for enclosures that have available 3-phase bolted short-circuit currents of 10,000 amperes rms or less.


2 Column B specifies the MFD for enclosures that have a maximum available 3-phase bolted short-circuit currents greater than 10,000 and less than or equal to 15,000 amperes rms.


3 Column C specifies the MFD for enclosures that have a maximum available 3-phase bolted short-circuit currents greater than 15,000 and less than or equal to 20,000 amperes rms.


4 Not Applicable – MSHA doesn’t allow aluminum wall or covers to be
1/4 inch or less in thickness (Section 18.31).


(1) For values not included in the table, the following formulas on which the table is based may be used to determine the minimum free distance.


(i) Steel Wall/Cover:



(ii) Aluminum Wall/Cover:




Where C is 1.4 for 2,400 volt systems or 3.0 for 4,160 volt systems, Isc is the 3-phase short circuit current in amperes of the system, t is the clearing time in seconds of the outby circuit-interrupting device and d is the thickness in inches of the metal wall/cover adjacent to an area of potential arcing.

(2) The minimum free distance must be increased by 1.5 inches for 4,160 volt systems and 0.7 inches for 2,400 volt systems when the adjacent wall area is the top of the enclosure. If a steel shield is mounted in conjunction with an aluminum wall or cover, the thickness of the steel shield is used to determine the minimum free distances.


(p) The following static pressure test must be performed on each prototype design of explosion-proof enclosures containing high-voltage switchgear prior to the explosion tests. The static pressure test must also be performed on every explosion-proof enclosure containing high-voltage switchgear, at the time of manufacture, unless the manufacturer uses an MSHA accepted quality assurance procedure covering inspection of the enclosure. Procedures must include a detailed check of parts against the drawings to determine that the parts and the drawings coincide and that the minimum requirements stated in part 18 have been followed with respect to materials, dimensions, configuration and workmanship.


(1) Test procedure. (i) The enclosure must be internally pressurized to at least the design pressure, maintaining the pressure for a minimum of 10 seconds.


(ii) Following the pressure hold, the pressure must be removed and the pressurizing agent removed from the enclosure.


(2) Acceptable performance. (i) The enclosure during pressurization must not exhibit –


(A) Leakage through welds or casting; or


(B) Rupture of any part that affects the explosion-proof integrity of the enclosure.


(ii) The enclosure following removal of the pressurizing agents must not exhibit –


(A) Visible cracks in welds;


(B) Permanent deformation exceeding 0.040 inches per linear foot; or


(C) Excessive clearances along flame-arresting paths following retightening of fastenings, as necessary.


[67 FR 10999, Mar. 11, 2002; 69 FR 68078, Nov. 23, 2004; 69 FR 70752, Dec. 7, 2004]


§ 18.54 High-voltage continuous mining machines.

(a) Separation of high-voltage components from lower voltage components. In each motor-starter enclosure, barriers, partitions, and covers must be provided and arranged so that personnel can test and troubleshoot low- and medium-voltage circuits without being exposed to energized high-voltage circuits. Barriers or partitions must be constructed of grounded metal or nonconductive insulating board.


(b) Interlock switches. Each removable cover, barrier, or partition of a compartment in the motor-starter enclosure providing direct access to high-voltage components must be equipped with at least two interlock switches arranged to automatically de-energize the high-voltage components within that compartment when the cover, barrier, or partition is removed.


(c) Circuit-interrupting devices. Circuit-interrupting devices must be designed and installed to prevent automatic re-closure.


(d) Transformers supplying control voltages. (1) Transformers supplying control voltages must not exceed 120 volts line to line.


(2) Transformers with high-voltage primary windings that supply control voltages must incorporate a grounded electrostatic (Faraday) shield between the primary and secondary windings. Grounding of the shield must be as follows:


(i) Transformers with an external grounding terminal must have the shield grounded by a minimum of No. 12 A.W.G. grounding conductor extending from the grounding terminal to the equipment ground.


(ii) Transformers with no external grounding terminal must have the shield grounded internally through the transformer frame to the equipment ground.


(e) Onboard ungrounded, three-phase power circuit. A continuous mining machine designed with an onboard ungrounded, three-phase power circuit must:


(1) Be equipped with a light that will indicate a grounded-phase condition;


(2) Have the indicator light installed so that it can be observed by the operator from any location where the continuous mining machine is normally operated; and


(3) Have a test circuit for the grounded-phase indicator light circuit to assure that the circuit is operating properly. The test circuit must be designed so that, when activated, it does not require removal of any electrical enclosure cover or create a double-phase-to-ground fault.


(f) High-voltage trailing cable(s). High-voltage trailing cable(s) must conform to the ampacity and outer dimensions specified in Table 10 of Appendix I to Subpart D of this part. In addition, the cable must be constructed with:


(1) 100 percent semi-conductive tape shielding over each insulated power conductor;


(2) A grounded metallic braid shielding over each insulated power conductor;


(3) A ground-check conductor not smaller than a No. 10 A.W.G.; or if a center ground-check conductor is used, not smaller than a No. 16 A.W.G. stranded conductor; and


(4) Either a double-jacketed or single-jacketed cable as follows:


(i) Double jacket. A double-jacketed cable consisting of reinforced outer and inner protective layers. The inner layer must be a distinctive color from the outer layer. The color black must not be used for either protective layer. The tear strength for each layer must be more than 40 pounds per inch thickness and the tensile strength must be more than 2,400 pounds per square inch.


(ii) Single jacket. A single-jacketed cable consisting of one protective layer. The tear strength must be more than 100 pounds per inch thickness, and the tensile strength must be more than 4,000 pounds per square inch. The cable jacket must not be black in color.


(g) Safeguards against corona. Safeguards against corona must be provided on all 4,160-voltage circuits in explosion-proof enclosures.


(h) Explosion-proof enclosure design. The maximum pressure rise within an explosion-proof enclosure containing high-voltage switchgear must be limited to 0.83 times the design pressure.


(i) Location of high-voltage electrical components near flame paths. High-voltage electrical components located in high-voltage explosion-proof enclosures must not be coplanar with a single plane flame-arresting path.


(j) Minimum creepage distances. Rigid insulation between high-voltage terminals (Phase-to-Phase or Phase-to-Ground) must be designed with creepage distances in accordance with the following table:


Phase-to-phase voltage
Points of

measure
Minimum creepage distances (inches) for comparative tracking index (CTI) range
1
CTI ≥500
380 ≤CTI 175 ≤CTI CTI
2,4000-01.501.952.402.90
0-G1.001.251.551.85
4,1600-02.403.153.904.65
0-G1.501.952.402.90


1 Assumes that all insulation is rated for the applied voltage or higher.


(k) Minimum free distances. Motor-starter enclosures must be designed to establish the minimum free distance (MFD) between the wall or cover of the enclosure and uninsulated electrical conductors inside the enclosure in accordance with the following table:


Wall/cover thickness

(in)
Steel MFD (in)
Aluminum MFD (in)
A
1
B
2
C
3
A
1
B
2
C
3

1/4
2.84.35.8
4 NA

4 NA

4 NA

3/8
1.82.33.98.612.818.1

1/2
* 1.22.02.76.59.813.0

5/8
* 0.91.52.15.17.710.4

3/4
* 0.6* 1.11.64.16.38.6
1** 0.6* 1.02.94.56.2

* Note: The minimum electrical clearances must still be maintained in accordance with the minimum clearance table of § 18.24.


1 Column A specifies the MFD for enclosures that have available three-phase, bolted, short-circuit currents of 10,000 amperes root-mean-square (rms) value or less.


2 Column B specifies the MFD for enclosures that have maximum available three-phase, bolted, short-circuit currents greater than 10,000 and less than or equal to 15,000 amperes rms.


3 Column C specifies the MFD for enclosures that have maximum available three-phase, bolted, short-circuit currents greater than 15,000 and less than or equal to 20,000 amperes rms.


4 Not Applicable – MSHA does not allow aluminum wall or covers to be
1/4 inch or less in thickness. (See also § 18.31.)


(1) For values not included in the table, the following formulas, on which the table is based, may be used to determine the minimum free distance.


(i) Steel Wall/Cover:




(ii) Aluminum Wall/Cover:




Where “C” is 1.4 for 2,400 volt systems or 3.0 for 4,160 volt systems; “Isc” is the three-phase, short-circuit current in amperes of the system; “t” is the clearing time in seconds of the outby circuit-interrupting device; and “d” is the thickness in inches of the metal wall/cover adjacent to an area of potential arcing.

(2) The minimum free distance must be increased by 1.5 inches for 4,160 volt systems and 0.7 inches for 2,400 volt systems when the adjacent wall area is the top of the enclosure. If a steel shield is mounted in conjunction with an aluminum wall or cover, the thickness of the steel shield is used to determine the minimum free distances.


(l) Static pressure testing of explosion-proof enclosures containing high-voltage switchgear – (1) Prototype enclosures. The following static pressure test must be performed on each prototype design of an explosion-proof enclosure containing high-voltage switchgear prior to the explosion tests.


(i) Test procedure. (A) The enclosure must be internally pressurized to at least the design pressure, maintaining the pressure for a minimum of 10 seconds.


(B) Following the pressure hold, the pressure must be removed and the pressurizing agent removed from the enclosure.


(ii) Acceptable performance. (A) During pressurization, the enclosure must not exhibit:


(1) Leakage through welds or casting; or


(2) Rupture of any part that affects the explosion-proof integrity of the enclosure.


(B) Following removal of the pressurizing agents, the enclosure must not exhibit:


(1) Cracks in welds visible to the naked eye;


(2) Permanent deformation exceeding 0.040 inches per linear foot; or


(3) Excessive clearances along flame-arresting paths following retightening of fastenings, as necessary.


(2) Enclosures for production. Every explosion-proof enclosure containing high-voltage switchgear manufactured after the prototype was tested must undergo one of the following tests or procedures:


(i) The static pressure test specified in paragraph (l)(1)(i) of this section; or


(ii) An MSHA-accepted quality assurance procedure covering inspection of the enclosure.


(A) The quality assurance procedure must include a detailed check of parts against the drawings to determine that –


(1) The parts and the drawings coincide; and


(2) The requirements stated in part 18 have been followed with respect to materials, dimensions, configuration and workmanship.


(B) [Reserved]


[75 FR 17547, Apr. 6, 2010]


Subpart C – Inspections and Tests

§ 18.60 Detailed inspection of components.

An inspection of each electrical component shall include the following:


(a) A detailed check of parts against the drawings submitted by the applicant to determine that: (1) The parts and drawings coincide; and (2) the minimum requirements stated in this part have been met with respect to materials, dimensions, configuration, workmanship, and adequacy of drawings and specifications.


(b) Exact measurement of joints, journal bearings, and other flame-arresting paths.


(c) Examination for unnecessary through holes.


(d) Examination for adequacy of lead-entrance design and construction.


(e) Examination for adequacy of electrical insulation and clearances between live parts and between live parts and the enclosure.


(f) Examination for weaknesses in welds and flaws in castings.


(g) Examination for distortion of enclosures before tests.


(h) Examination for adequacy of fastenings, including size, spacing, security, and possibility of bottoming.


§ 18.61 Final inspection of complete machine.

(a) A completely assembled new machine or a substantially modified design of a previously approved one shall be inspected by a qualified representative(s) of MSHA. When such inspection discloses any unsafe condition or any feature not in strict conformance with the requirements of this part it shall be corrected before an approval of the machine will be issued. A final inspection will be conducted at the site of manufacture, rebuilding, or other locations at the option of MSHA.


(b) Complete machines shall be inspected for:


(1) Compliance with the requirements of this part with respect to joints, lead entrances, and other pertinent features.


(2) Wiring between components, adequacy of mechanical protection for cables, adequacy of clamping of cables, positioning of cables, particularly with respect to proximity to hydraulic components.


(3) Adequacy of protection against damage to headlights, push buttons, and any other vulnerable component.


(4) Settings of overload- and short-circuit protective devices.


(5) Adequacy of means for connecting and protecting portable cable.


§ 18.62 Tests to determine explosion-proof characteristics.

(a) In testing for explosion-proof characteristics of an enclosure, it shall be filled and surrounded with various explosive mixtures of natural gas and air. The explosive mixture within the enclosure will be ignited electrically and the explosion pressure developed therefrom recorded. The point of ignition within the enclosure will be varied. Motor armatures and/or rotors will be stationary in some tests and revolving in others. Coal dust having a minimum of 22 percent dry volatile matter and a minimum heat constant of 11,000 moist BTU (coal containing natural bed moisture but not visible surface water) ground to a fineness of minus 200 mesh U.S. Standard sieve series. At MSHA’s discretion dummies may be substituted for internal electrical components during some of the tests. Not less than 16 explosion tests shall be conducted; however, the nature of the enclosure and the results obtained during the tests will determine whether additional tests shall be made.


(b) Explosion tests of an enclosure shall not result in:


(1) Discharge of flame.


(2) Ignition of an explosive mixture surrounding the enclosure.


(3) Development of afterburning.


(4) Rupture of any part of the enclosure or any panel or divider within the enclosure.


(5) Permanent distortion of the enclosure exceeding 0.040 inch per linear foot.


(c) When a pressure exceeding 125 pounds per square inch (gage) is developed during explosion tests, MSHA reserves the right to reject an enclosure(s) unless (1) constructional changes are made that result in a reduction of pressure to 125 pounds per square inch (gage) or less, or (2) the enclosure withstands a dynamic pressure of twice the highest value recorded in the initial test.


[33 FR 4660, Mar. 19, 1968, as amended at 57 FR 61210, Dec. 23, 1992]


§ 18.63 [Reserved]

§ 18.65 Flame test of hose.

(a) Size of test specimen. (1) [Reserved]


(2) Hose – four specimens each 6 inches long by
1/2-inch wide by thickness of the hose.


(b) Flame-test apparatus. The principal parts of the apparatus within and/or appended to a 21-inch cubical test gallery are:


(1) A support stand with a ring clamp and wire gauze.


(2) A Pittsburgh-Universal Bunsen-type burner (inside diameter of burner tube 11 mm.), or equivalent, mounted in a burner placement guide in such a manner that the burner may be placed beneath the test specimen, or pulled away from it by an external knob on the front panel of the test gallery.


(3) A variable-speed electric fan and an ASME flow nozzle (16-8
1/2 inches reduction) to attain constant air velocities at any speed between 50-500 feet a minute.


(4) An electric timer or stopwatch to measure the duration of the tests.


(5) A mirror mounted inside the test gallery to permit a rear view of the test specimen through the viewing door.


(c) Mounting of test specimen. The specimen shall be clamped in a support with its free end centered 1 inch above the burner top. The longitudinal axis shall be horizontal and the transverse axis inclined at 45° to the horizontal. Under the test specimen shall be clamped a piece of 20-mesh iron-wire gauze, 5 inches square, in a horizontal position
1/4-inch below the pulley cover edge of the specimen and with about
1/2-inch of the specimen extending beyond the edge of the gauze.


(d) Procedure for flame tests. (1) The Bunsen burner, retracted from the test position, shall be adjusted to give a blue flame 3 inches in height with natural gas.


(2) The observation door of the gallery shall be closed for the entire test.


(3) The burner flame shall be applied to the free end of the specimen for 1 minute in still air.


(4) At the end of 1 minute the burner flame shall be removed, the ventilating fan turned on to give an air current having a velocity of 300 feet per minute, and the duration of flame measured.


(5) After the test specimen ceases to flame, it shall remain in the air current for at least 3 minutes to determine the presence and duration of afterglow. If a glowing specimen exhibits flame within 3 minutes the duration of flame shall be added to the duration of flame obtained according to paragraph (d) (4) of this section.


(e) Test requirements. The tests of the four specimens cut from any sample shall not result in either duration of flame exceeding an average of 1 minute after removal of the applied flame or afterglow exceeding an average of 3 minutes duration.


(f) Acceptance markings. (1) [Reserved]


(2) Hose – hose conduit accepted by MSHA as flame-resistant shall be marked as follows: Impressed letters, raised letters on depressed background, or printed letters with the words “Flame-Resistant, USMSHA No. __” at intervals not exceeding 3 feet. This number will be assigned to the manufacturer after the sample has passed the tests. The letters and numbers shall be at least
1/4-inch high.


[33 FR 4660, Mar. 19, 1968, as amended at 43 FR 12314, Mar. 24, 1978; 73 FR 80612, Dec. 31, 2008]


§ 18.66 Tests of windows and lenses.

(a) Impact tests. A 4-pound cylindrical weight with a 1-inch-diameter hemispherical striking surface shall be dropped (free fall) to strike the window or lens in its mounting, or the equivalent thereof, at or near the center. Three of four samples shall withstand without breakage the impact according to the following table:


Lens diameter, (D), inches
Height of fall, inches
D6
4≤D9
5≤D15
6≤D24

Windows or lenses of smaller diameter than 1 inch may be tested by alternate methods at the discretion of MSHA.

(b) Thermal-shock tests. Four samples of the window or lens will be heated in an oven for 15 minutes to a temperature of 150 °C. (302 °F.) and immediately upon withdrawal of the samples from the oven they will be immersed in water having a temperature between 15 °C. (59 °F) and 20 °C. (68 °F.). Three of the four samples shall show no defect or breakage from this thermal-shock test.


§ 18.67 Static-pressure tests.

Static-pressure tests shall be conducted by the applicant on each enclosure of a specific design when MSHA determines that visual inspection will not reveal defects in castings or in single-seam welds. Such test procedure shall be submitted to MSHA for approval and the specifications on file with MSHA shall include a statement assuring that such tests will be conducted. The static pressure to be applied shall be 150 pounds per square inch (gage) or one and one-half times the maximum pressure recorded in MSHA’s explosion tests, whichever is greater.


§ 18.68 Tests for intrinsic safety.

(a) General:


(1) Tests for intrinsic safety will be conducted under the general concepts of “intrinsically safe” as defined in Subpart A of this part. Further tests or requirements may be added at any time if features of construction or use or both indicate them to be necessary. Some tests included in these requirements may be omitted on the basis of previous experience.


(2) Intrinsically safe circuits and/or components will be subjected to tests consisting of making and breaking the intrinsically safe circuit under conditions judged to simulate the most hazardous probable faults or malfunctions. Tests will be made in the most easily ignitable mixture of methane or natural gas and air. The method of making and breaking the circuit may be varied to meet a particular condition.


(3) Those components which affect intrinsic safety must meet the following requirements:


(i) Current limiting components shall consist of two equivalent devices each of which singly will provide intrinsic safety. They shall not be operated at more than 50 percent of their ratings.


(ii) Components of reliable construction shall be used and they shall be so mounted as to provide protection against shock and vibration in normal use.


(iii) Semiconductors shall be amply sized. Rectifiers and transistors shall be operated at not more than two-thirds of their rated current and permissible peak inverse voltage. Zener diodes shall be operated at not more than one-half of their rated current and shall short under abnormal conditions.


(iv) Electrolytic capacitors shall be operated at not more than two-thirds of their rated voltage. They shall be designed to withstand a test voltage of 1,500 volts.


(4) Intrinsically safe circuits shall be so designed that after failure of a single component, and subsequent failures resulting from this first failure, the circuit will remain intrinsically safe.


(5) The circuit will be considered as intrinsically safe if in the course of testing no ignitions occur.


(b) Complete intrinsically safe equipment powered by low energy batteries:


(1) Short-circuit tests shall be conducted on batteries at normal operating temperature. Tests may be made on batteries at elevated temperature if such tests are deemed necessary.


(2) Resistance devices for limiting short-circuit current shall be an integral part of the battery, or installed as close to the battery terminal as practicable.


(3) Transistors of battery-operated equipment may be subjected to thermal “run-away” tests to determine that they will not ignite an explosive atmosphere.


(4) A minimum of 1,000