methane-monitoring system that is essential to its operation as a certified methane-monitoring system.

(j) "Explosion proof" means that a component or group of components (subassembly) is so constructed and protected by an enclosure with or without a flame arrester (s) that, if a flammable mixture of gas is ignited within the enclosure, it will withstand the resultant pressure without damage to the enclosure and/or flame arrester(s). Also the enclosure and/or flame arrester(s) shall prevent the discharge of flame from within either the enclosure or the flame arrester, or the ignition of any flammable mixture that surrounds the enclosure and/or flame arrester.1

(k) "Normal operation" means that performance of each component as well as of the entire assembly of the methanemonitoring system is in conformance with the functions for which it was designed and for which it was tested by the Bureau.

(1) "Flame arrester" means a device so constructed that it will prevent propagation of flame or explosion from within the unit of which it is part to a surrounding flammable mixture.

(m) "Intrinsically safe equipment and circuitry" means equipment and circuitry that are incapable of releasing enough electrical or thermal energy under normal or abnormal conditions to cause ignition of a flammable mixture of the most easily ignitable composition.

(n) "Fail safe" means that the circuitry of a methane-monitoring system shall be so designed that electrical failure of a component which is critical in the Bureau's opinion will result in deenergizing the methane-monitoring system and the machine or equipment of which it is a part.

part. No charge is made for such consultation and no written report thereof will be made to the applicant.

§ 27.4 Applications.

(a) No investigation or testing for certification will be undertaken by the Bureau except pursuant to a written application, in duplicate, accompanied by all drawings, specifications, descriptions, and related materials and also a check, bank draft, or money order, payable to the Bureau of Mines, to cover the fees. The application and all related matters and correspondence concerning it shall be addressed to the Bureau of Mines, 4800 Forbes Avenue, Pittsburgh, Pa., 15213, Attention: Electrical-Mechanical Testing.

(b) Drawings, specifications, and descriptions shall be adequate in detail to identify fully all components and subassemblies that are submitted for investigation, and shall include wiring and block diagrams. All drawings shall include title, number, and date; any revision dates and the purpose of each revision shall also be shown on the drawing.

(c) For a complete investigation leading to certification, the applicant shall furnish all necessary components and material to the Bureau. The Bureau reserves the right to require more than one of each component, subassembly, or assembly for the investigation. Spare parts and expendable components, subject to wear in normal operation, shall be supplied by the applicant to permit continuous operation during test periods. The applicant shall furnish special tools necessary to assemble or disassemble any component or subassembly for inspection or test.

(d) The applicant shall submit a plan of inspection of components at the place of manufacture or assembly. The applicant shall furnish to the Bureau a copy of any factory-inspection form or equiv'alent with the application. The form shall direct attention to the points that must be checked to make certain that all components or subassemblies of the complete assembly are in proper condition, complete in all respects, and in agreement with the drawings, specifications, and descriptions filed with the Bureau.

(e) The applicant shall furnish to the Bureau complete instructions for operating the assembly and servicing components. After completion of the Bureau's investigation, and before certification, if any revision of the instructions is required, a revised copy thereof shall be submitted to the Bureau for inclusion with the drawings and specifications. § 27.5 Letter of certification.

(a) Upon completion of investigation of a methane-monitoring system, or component or subassembly thereof, the Bureau will issue to the applicant either a letter of certification or a written notice of disapproval, as the case may require. If a letter of certification is issued, no test data or detailed results of tests will accompany it. If a notice of disapproval is issued, it will be accompanied by details of the defects, with a view to possible correction. The Bureau will not disclose, except to the applicant or his authorized representative, any information because of which a notice of disapproval has been issued.

(b) A letter of certification will be accompanied by an appropriate cautionary statement specifying the conditions to be observed for operating and maintaining the device(s) and to preserve its certified status.

§ 27.6 Certification of components.

In accordance with § 27.4, manufacturers of components may apply to the Bureau to issue a letter of certification. To qualify for certification, electrical components shall conform to the prescribed inspection and test requirements and the construction thereof shall be adequately covered by specifications officially recorded and filed with the Bureau. Letters of certification may be cited to fabricators of equipment intended for use in a certified methanemonitoring system as evidence that further inspection and test of the components will not be required.

(c) Each series of tests to determine adequacy of design, materials, and/or construction__ (d) Tests to determine safe operation and performance of a complete methane-monitoring system---.

(e) Tests to determine intrinsic safety---

(f) Final examination and recording of drawings and specifications requisite to issuing a letter of certification

(g) Examining and recording drawings and specifications requisite to issuing an extension of certification, each 4 hours or fraction thereof

(h) Tests to assist an applicant in evaluating equipment intended for certification may be made at the discretion of the Bureau. Written requests for such tests shall be directed to the Bureau of Mines, 4800 Forbes Avenue, Pittsburgh, Pennsylvania, 15213, Attention: Electrical-Mechanical Testing. A deposit of $200 shall be paid in advance when such tests have been authorized. The fees charged shall depend on the work performed based on normal charges. Any surplus will be refunded at the completion of the work, or applied to future work, on the same device, as directed by the applicant----.

If an applicant is unable to determine the exact fee that should be submitted

§ 27.9 Date for conducting tests.

The application, payment of necessary fees, and submission of required material will determine the order of precedence for testing when more than one application is pending. The applicant will be notified of the date on which tests will begin.

NOTE: If an assembly, subassembly, or component fails to meet any of the requirements, testing of it may be suspended and other items may be tested. However, if the cause of failure is corrected, testing will be resumed after completing such other test work as may be in progress.

§ 27.10 Conduct of investigations, tests, and demonstrations.

The Bureau shall hold as confidential and shall not disclose principles or patentable features, nor shall it disclose any details of drawings, specifications, or related materials. The conduct of all investigations, tests, and demonstrations shall be under the sole direction and control of the Bureau, and any other persons shall be present only as observers, except as noted in paragraph (b) of this section.

(a) Prior to the issuance of a letter of certification, only Bureau personnel, representatives of the applicant, and such other persons as are mutually agreed upon may observe the investigations or tests.

(b) When requested by the Bureau, the applicant shall provide assistance in assembling or disassembling components, subassemblies, or assemblies for testing, preparing components, subassemblies, or assemblies for testing, and operating the system during the tests.

(c) After the issuance of a letter of certification, the Bureau may conduct such public demonstrations and tests of the certified methane-monitoring system or components as it deems appropriate.

Extension of certification.

feature of a certified system or comIf an applicant desires to change any ponent, he shall first obtain the Bureau's approval of the change, pursuant to the following procedure:

(a) Application shall be made as for an original certification, requesting that the existing certification be extended to cover the proposed changes. The application shall include complete drawings, specifications, and related data, showing the changes in detail.

(b) The application will be examined by the Bureau to determine whether inspection and testing of the modified system or component or of a part will be required. The Bureau will inform the applicant whether testing is required; the component or components and related material to be submitted for that purpose; and the fee for testing.

(c) If the proposed modification meets the requirements of this part, a formal extension of certification will be issued, accompanied by a list of revised drawings and specifications which the Bureau has added to those already on file. § 27.12 Withdrawal of certification.

The Bureau reserves the right to rescind for cause any certification issued under this part.

Subpart B-Construction and Design Requirements

§ 27.20 Quality of material, workmanship, and design.

(a) The Bureau will test only equipment that, in its opinion, is constructed of suitable materials, is of good workmanship, is based on sound engineering principles, and is safe for its intended use. Since all possible designs, arrangements, or combinations of components cannot be foreseen, the Bureau reserves the right to modify the construction and design requirements of components or subassemblies and the tests to obtain the degree of protection intended by the tests described in Subpart C of this part.

(b) Unless otherwise noted, the requirements stated in this part shall apply to explosion-proof enclosures and intrinsically safe circuits.

(c) All components, subassemblies, and assemblies shall be designed and con

(1) A means which shall be made to function automatically to deenergize the machine or equipment when actuated by the methane detector at a methane concentration of 2.0 volume percent and at all higher concentrations in the mine atmosphere.

(i) For an electric-powered machine or equipment energized by means of a trailing cable, the power-shutoff component shall, when actuated by the methane detector, cause a control circuit to shut down the machine or equipment on which it is installed; or it shall cause a control circuit to deenergize both the machine or equipment and the trailing cable.

NOTE: It is not necessary that power be controlled both at the machine and at the outby end of the trailing cable.

or

(ii) For a battery-powered machine equipment, the methane-monitor power-shutoff component shall, when actuated by the methane detector, cause a control circuit to deenergize the machine or equipment as near as possible to the battery terminals.

(iii) For a diesel-powered machine or equipment, the power-shutoff component, when actuated by the methane detector, shall shut down the prime mover and deenergize all electrical components of the machine or equipment. Batteries are to be disconnected as near as possible to the battery terminals. Headlights which are approved under part 20 of this subchapter (Schedule 10, or any revision thereof) are specifically exempted from this requirement.

(2) An arrangement for testing the power-shutoff characteristic to determine whether the power-shutoff component is functioning properly.

Subpart C-Test Requirements § 27.30 Inspection.

A detailed inspection shall be made by the Bureau of the equipment and all components and functions related to safety in operation, which shall include:

A methane-monitoring system shall be tested by the Bureau to determine its functional performance, and its explosion-proof and other safety characteristics. Since all possible designs, arrangements, or combinations cannot be foreseen, the Bureau reserves the right to make any tests or to place any limitations on equipment, or components or subassemblies thereof, not specifically covered herein, to determine and assure the safety of such equipment with regard to explosion and fire hazards.

§ 27.32 Tests to determine performance of the system.

3

(a) Laboratory tests for reliability and durability. Five hundred successful consecutive tests for gas detection, alarm action, and power shutoff in ducted to demonstrate acceptable pernatural gas-air mixtures shall be conformance as to reliability and durability of a methane-monitoring system. The tests shall be conducted as follows:

(1) The methane detector component shall be placed in a test gallery into which natural gas shall be made to enter at various rates with sufficient turbulence for proper mixing with the air in the gallery. To comply with the requirements of this test, the detector shall provide an impulse to actuate an alarm at a predetermined percentage of gas and also provide an impulse to actuate a power shutoff at a second predetermined percentage of gas. (See §§ 27.21, 27.22, 27.23, and 27.24.) *

(b) Field tests. The Bureau reserves the right to conduct tests, similar to those stated in paragraph (a) of this section, in underground workings to

2 Normal replacements and adjustments shall not constitute a failure.

3 Investigation has shown that, for practical purposes, natural gas (containing a high percentage of methane) is a satisfactory substitute for pure methane in these tests.

4 At the option of the Bureau, these tests will be conducted with dust or moisture added to the atmosphere within the gallery.

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