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VOLUME II INTERPRETATION, APPLICATION AND GUIDELINES ON ENFORCEMENT OF 30 CFR Subpart C .... Inspections and Tests 18.61 Final Inspection of Complete Machine Inspection of Longwall Lighting Systems Longwall lighting systems shall be completely installed at the time of Approval and Certification Center conducts an inspection of a longwall mining system to be used in underground coal mines. 18.68 Tests for Intrinsic Safety Requirements When Using Permissible Page Phones as a Longwall Pre-Start Alarm The face communication system typically used on longwalls is a page phone system that is electrically segregated from the longwall and any other phone system and consists of telephones previously approved as permissible under 30 CFR Part 23. When permissible page phones are used as the audio transducers of a pre-start alarm system, additional requirements must be met. A pre-start alarm system may be accepted by the Approval and Certification Center as intrinsically safe if, in addition to the applicable requirements of 30 CFR Part 18, the following conditions are met:
Paragraph 18.68(c)(3) of 30 CFR Part 18 requires that cables and wires carrying intrinsically safe currents shall not be intermingled with nonintrinsically safe cables and wires. The following shall be regarded as intermingling:
To ensure compliance with this requirement, a note stating that"wiring for nonintrinsically safe circuits shall not be intermingled with wiring for intrinsically safe circuits" shall be required on all wiring and schematic diagrams depicting both intrinsically safe and nonintrinsically safe circuits. Clarification of 30 CFR Section 18.68 and 30 CFR Section 18.41 Recent evaluations of intrinsically safe circuits using metallic conductors contained in the same cable with conductors on non-intrinsically safe circuits have determined that the specified intrinsically safe circuits cannot be considered by 30 CFR Section 18.68 to be intrinsically safe in this application.Therefore, the approval documentation should not identify these circuits as intrinsically safe. If the I.S. evaluation investigation is specified, a note must be included stating: In this application the circuit is not accepted as being intrinsically safe.This implies, with reference to paragraph 18.41(a)(2)(ii), that inline non-explosion proof connectors which are dependent on an ISC pilot interlock circuit for permissibility will no longer be accepted. Box mounted non-explosion proof connectors may depend on an ISC pilot interlock circuit for permissibility if the interlock consists of only a short jumper wire between two pins of the plug which mates with the box mounted connector. Control Circuit Wiring on Permissible Equipment The Mine Safety and Health Administration (MSHA) has identified a potential hazard associated with start and stop switches and control circuit wiring on some permissible electric equipment.The problem involves sticking start switches on permissible machines that have start switches connected in parallel with stop switches. When a stop switch operating shaft binds and holds in a stop switch, the function controlled by the switch cannot be performed and the problem is easily detectable and repairable. However,when a start switch operating shaft binds and holds in a start switch, the function controlled by the switch can usually be performed and the problem may not be easily detectable. When this condition occurs on a machine where start and stop switches are connected in parallel, one or more stop switches become ineffective. As a result, the machine could be operated with one or more stop switches incapable of performing the functions for which they were intended without the machine operator being fully aware of the problem. This condition would present a serious hazard if the switch that became ineffective was an emergency stop switch, panic bar switch, or any other stop switch that must perform properly in an emergency situation. MSHA recommends that no start switch be connected in parallel with any stop switch. While most mining equipment control circuits are designed according to this recommendation, there are types of equipment that are designed so that a binding start switch will make one or more stop switches ineffective. These types of equipment are usually multiple operating station machines, such as roof bolting machines, that have start and stop functions at various positions around the machine. At this time, MSHA does not propose to require immediate modification of this wiring as a condition of approval or to require immediate rewiring of equipment in the field. However,MSHA recommends that equipment manufacturers take appropriate action to ensure that the control circuits on newly manufactured machines are wired so that no stop switch can become ineffective if any start switch becomes stuck in the "on" position. To expedite the processing of wiring modifications to control circuits on previously approved equipment relating to this recommendation, MSHA will permit the original equipment manufacturer to document the modified circuit in place of the existing circuit via the Stamped Notification Acceptance Program(SNAP) administered by the Approval and Certification Center. MSHA also recommends that operators take appropriate action to ensure that the control circuits on machines in the field a rewired so that no stop switch can become ineffective if any start switch becomes stuck in the "on" position. Operators who seek to modify affected equipment in the field should contact the equipment manufacturer for assistance. Operators field modification requests covering these changes will be processed by MSHA District Offices and the Approval and Certification Center on a priority basis. Pending any modification of affected machines, coal mine operators should check the machines, as part of the weekly examinations required by 30 CFR 75.512, to ensure that start switches are not binding and sticking in the "on"position. In addition, if a machine operator detects a binding start or stop switch, the condition should be reported immediately so it can be corrected by cleaning and lubricating the operating shaft or other appropriate means. 18.69 Adequacy Tests Sintered Metallic Friction Materials Used for Brakes on Permissible Equipment The Mine Safety and Health Administration (MSHA) has identified a potential hazard associated with the use of sintered metallic friction materials as brake linings on permissible electric equipment. The problem is during normal braking, considerable amounts of hot, glowing particles may be thrown from the friction material/brake disc mating surfaces into the surrounding mine environment. Friction materials of this type have been used on both the service and emergency brakes, as new and replacement linings. No sintered metallic friction materials are permitted for such use, unless they are housed in explosion-proof enclosures or other enclosures that prohibit the outside atmosphere from entering the enclosure. PART 28 .... FUSES FOR USE WITH DIRECT CURRENT IN PROVIDING SHORT-CIRCUIT PROTECTION FOR TRAILING CABLES IN COAL MINES Subpart E .... Construction, Performance, and Testing Requirements 28.40 Construction and Performance Requirements The Approval and Certification Center has provided clarification of the phrases: (1) "initial current interruption," (2) "evidence of restriking," and (3) "superficial damage," as stated inoperables 28.40(e) and (f). In an effort to eliminate confusion and ensure uniform interpretation the following definitions are provided for your information:
PART 36 .... APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Neutral Start Methods on MSHA Approved Equipment Equipment submitted for approval under Part 36 must be equipped with a neutral start method that ensures that the engine cranking torque will not be transmitted through the powertrain and cause machine movement. PART 75 .... MANDATORY SAFETY STANDARDS - UNDERGROUND COAL MINES 75.1719 Illumination Use of Alternate Lights on Statement for Test and Evaluation (STE) Application This policy establishes requirements for the evaluation of alternate lighting fixtures specified in STE applications whose requirements are identified in Federal Register Volume 41,No. 64, Thursday, April 1, 1976, page 14108. Photometric data is not required to be submitted with an STE application for a lighting system using alternate lighting fixtures that have been found to have similar photometric patterns. On the following page is a list of headlights and machine lights that are considered photometrically inter-changeable. The headlight fixtures use 50 watt, 12 volt, type MR-16 (EXN) and the machine lights use 100 watt, 120 volt, type A-19 incandescent bulbs. Presently, only certain pairs of lights have been evaluated and found to have similar photometric patterns. Because of this similarity, the Approval and Certification Center will accept both fixtures to be listed on an STE application, while requiring actual photometric data on only one lighting system. The other lighting fixture of the pari may be listed as an alternate on the machine layout drawing. This policy does not limit the number of lighting fixture alternates that may be specified in an STE application. However, if the alternate fixture is not part of a pair, the actual photometric data is required for each system. This policy does not authorize interchanging the lights on machines indiscriminately. When the STE contains a set of lights that are alternate to each other, they may be interchanged on the machine to which the STE applies. No further paperwork or evaluation is then necessary. If the STE for the machine lists only one of the lights of the pair, the appropriate field modification must be submitted to document the permissibility of the light. No photometric data is required. HEADLIGHTS
(with bulb type 50 watt, 12 volt, MR-16 (EXN) clear, incandescent)
MACHINE LIGHTS
(with bulb type 100 watt, 120 volt, type A-19, inside frosted, incandescent)
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