# Code of Federal Regulations/Title 30/Chapter I/Part 7

From the U.S. Government Printing Office on Google Books, revised as of July 1, 1993. (Commons file)

### PART 7—TESTING BY APPLICANT OR THIRD PARTY
#### Subpart A—General Provisions

Sec.
7.1 Purpose and scope.
7.2 Definitions.
7.3 Application procedures and requirements.
7.4 Product testing.
7.5 Issuance of approval.
7.6 Approval marking record.
7.7 Quality assurance.
7.8 Post-approval preduct audit.
7.9 Revocation.

#### Subpart B—Brattice Cloth and Ventilation Tubing

7.21 Purpose and effective date.
7.22 Definitions.
7.23 Application requirements.
7.24 Technical requirements.
7.25 Critical characteristics.
7.26 Flame test apparatus.
7.27 Test for flame resistance of brattice cloth.
7.28 Test for flame resistance of rigid ventilation tubing.
7.29 Approval marking.
7.30 Post-approval product audit.
7.31 New technology.

#### Subpart C—Battery Assemblies

7.41 Purpose and effective date,
7.42 Definitions.
7.43 Application requirements.
7.44 Technical requirements.
7.45 Critical characteristics.
7.46 Impact test.
7.47 Deflection temperature test.
7.48 Acid resistance test.
7.49 Approval marking.
7.50 Post-approval product audit.
7.51 Approval checklist.
7.52 New technology.

#### Subpart D—Multiple-Shot Blasting Units

7.61 Purpose and effective date.
7.62 Definitions.
7.63 Application requirements.
7.64 Technical requirements.
7.65 Critical characteristics.
7.66 Output energy test.
7.67 Construction test.
Sec.
7.68 Firing line terminals test.
7.69 Approval marking.
7.70 Post-approval product audit.
7.71 Approval checklist.
7.72 New technology.

#### Subpart J—Electric Motor Assemblies

7.301 Purpose and effective date.
7.302 Definitions.
7.303 Application requirements.
7.304 Technical requirements.
7.305 Critical characteristics.
7.306 Explosion tests.
7.307 Static pressure test.
7.308 Lockwasher equivalency test.
7.309 Approval marking.
7.310 Post-approval product audit.
7.311 Approval checklist.
APPENDIX 1 TO SUBPART J OF PART 7

#### Subpart K—Electric Cables, Signaling Cables, and Cable Spice Kits

7.401 Purpose and effective date.
7.402 Definitions.
7.403 Application requirements.
7.404 Technical requirements.
7.405 Critical characteristics.
7.406 Flame test apparatus.
7.407 Test for flame resistance of electric cables and cable splices.
7.408 Test for flame resistance of signaling cables.
7.409 Approval markings.
7.410 Post-approval product audit.
7.411 New technology.
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 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 effect on safety and for which testing or Inspection LS required prior to shipment to ensure conformity with the technical requirements under which the approval was issued,
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 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. 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 PR 25569. July 7, 1988]

#### § 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. RR # 1. Box 251, Industrial Park Road, Triadelphia. West Virginia 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 resentative responsible for answering any questions regarding the application;
(4) If appropriate, 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 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 pro change to the previously approved product;
(3) Drawings and specifications which show the change in detail;
(4) A statement 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. 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, specified in the appropriate subpart, and that the applicant will perform the quality assurance functions specified in 5 7.7. For B 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 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. (Approved by the Office of Management and Budget under control number 1219—0100)

#### § 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 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, instruments shall be calibrated at least as frequently as, and according to, the instrument manufacturer's specifications, using calibration traceable to those set by the National Bureau of Standards, US. 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 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.
(Approved by the Office of Management and Budget under control number 12190100)
[53 PR 23500. June 22. 1988; 53 FR 25569, July 7. 1988]

#### § 7.5 Issuance of approval.

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

(a) Each approved product shall have an approval marking, as specified in the appropriate subpart of this part.
(b) For 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 approval marking. The record retention period shall be at least the expected shelf life and service life of the product.
(Approved by the Office or Management and Budget under control number 12190100)

#### § 7.7 Quality assurance.

Applicants granted an approval or 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, wing 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 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.
(Approved by the Office or and Budget under control number 12190100)

#### § 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 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 my 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 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 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 pose 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—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.
(Approved by the Office of Management and Budget under control number 1219-0100)

#### § 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 ⅛ inch thick Marinite or equivalent insulating material yielding inside dimensions approximately 58 inches long, 41 inches high, and 30 inches wide;
(b) Two ⅔-inch diameter steel J hooks and a 3⁄16-inch diameter steel rod to support the sample located approximately 2 3⁄16-inches from the front and back ends of the test gallery, 1½-inches from the ceiling insulation and centrally located in the gallery along its length. Samples shalt be suspended to preclude folds or wrinkles;
(c) A tapered 16-gauge stainless steel duct section tapering from a crass 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 1⅜-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 conaldered 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 teats.
(Approved by the Office of Management and Budget under control number 1219-0100)

#### § 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.
(Approved by the Office of Management and Budget under control number 1219-0100)

#### § 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 ap- proved 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 sufficent 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.
(Approved by the Office of Management and Budget under control number 1219-0100)

#### § 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. maximum. 1,001 to 2,000 lbs. 2,001 to 4,500 lbs. Over 4,500 lbs.... | 10 gauge or ⅛" nominal 7 gauge or 3/16" nominal 3 gauge or ¼" nominal 0 gauge or 3/14" 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:
${\frac {(N)(R)}{950}}=M$
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.
(1) 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 ½-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.
(Approved by the Office of Management and Budget under control number 12190100)

#### § 7.47 Deflection temperature test.

(a) Test procedures. (1) Prepare two samples for testing that measure 5 inches by ½ 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 ⅛ 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 ⅛ 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 8 for the other sample.
(b) Acceptable performance, Neither sample shall have a deflection greater than .010 inch at 180 °F (82 °C).
(Approved by the Office of Management and Budget under control number 1219-D100)
[53 PR 23600, June 22, 1988; 53 FR 25569, July 7, 1988]

#### § 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 (H$_2$SO$_4$) by mixing 853 ml of water with 199 ml of sulfuric acid (H$_2$SO$_4$,) 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.
(Approved by the Office of Management and Budget under control number 1219-9100)

#### § 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.
(Approved by the Office of Management and Budget under control number 1219-6200)

#### § 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.
(Approved by the Office of Management and Budget under control number 1219-0100)

#### § 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 fits operation to prevent accidental firing:
(2) Operate only when the voltage necessary to produce the required firing current is available to the blasting circuit.
(e) Firing tine 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 per- formed on the blasting unit subsequent to the output energy test of § 7.86.
(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, if 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 ¢o 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.
(Approved by the Office of Management and Budget under control number 1219-0100)

#### § 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 J—Electric Motor Assembles

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 tn 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 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 com. prised 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 & 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) | Clearances (inches) |
| Phase-to-phase voltage (rms) | Phase-to-phase | Phase-to-ground or control circuit |
| 0 to 250 251 to 600 601 to 1000 1001 to 2400 2401 to 4160 | 0.25 0.28 0.61 1.4 3.0 | 0.25 0.25 0.25 0.6 1.4 |
(d) Parts whose dimensions 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 Mine Safety and Health Administration, Department of Labor, Approval and Certification Center, RR 1, Industrial Park Road, Triadelphia, WV 26059, or at the Office of the Federal Register, 800 N. Capitol Street, NW., 7th Floor, suite 700, Washington, DC.
(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 strator frame, it shall be impossible to insert a 0.0015 inch thickness gauge to a depth exceeding ¼" depth 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 ⅛ inch. If the distance is ⅛ to ¼ inch, the diametrical clearance for the pole bolt shall not exceed 1/64 inch for not less than ½ 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: