Program Policy Manual - VOLUME V - Mine Safety and Health ...

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MSHA PROGRAM POLICY MANUAL VOLUME V 75.310 Installation of Main Mine Fans The purpose of paragraph (b)(1) is to ensure that the mine fan is provided with a dependable power supply that will not be affected by short circuits, ground faults, or overloads occurring in mine power circuits. Transformers or other power sources supplying mine fan circuits may also supply power to other circuits, provided that such circuits are protected in a manner ensuring that any malfunction in the other circuits will cause automatic deenergization of the affected circuit and will not affect the mine fan circuit. 75.323 Actions for Excessive Methane Section 75.323 specifies actions to be performed for excessive methane. Neither the Act nor the regulations provide that a mere presence of methane gas in excess of 1.0 percent is per se a violation. A violation would exist if a mine operator, upon becoming aware of the presence of excessive methane fails to perform the actions specified in Section 75.323. 75.325 Air Quantity (a)(3)The name plate quantity of the machine mounted dust collector or diffuser fan is acceptable to meet the requirements of 30 CFR 75.325(a)(3) and 75.371(j). If the operator submits the nameplate quantity in the approved ventilation plan as the operating volume, this is the minimum quantity that must be maintained at all times. If this quantity is not maintained, if the measured operating capacity reveals that the name plate quantity is not indicative of actual conditions, or if respirable dust samples indicate that this quantity is not sufficient, appropriate enforcement action shall be taken and plan revisions shall be necessary. Paragraph (f) requires that the minimum ventilating air quantity for an individual unit of diesel-powered equipment must be provided. This requirement includes entries under paragraph (f) (3) where diesel-powered equipment is being operated outby the loading point in areas of the mine developed on or after April 25, 1997. Such entries include crosscuts, dead-end spurs and any other area where such equipment is positioned to allow passage of other equipment or personnel, or entering an area to place or retrieve supplies. The minimum ventilating air quantity for a unit of diesel-powered equipment is established based on the quantity of air specified on the unit’s approval plate. The approval plate quantity is based on testing of the diesel exhaust gas concentrations of carbon monoxide (CO) and Oxides of Nitrogen measured as nitrogen January 2013 (Release V-45) 41
MSHA PROGRAM POLICY MANUAL VOLUME V dioxide (NO2). The approval plate quantity is the quantity of air that is required to dilute the concentration of CO and NO2 at the tailpipe to the Threshold-Limit-Values (TLVs) specified in 75.322. The TLVs are established to protect persons from adverse health effects from exposure to the specified contaminates. The TLV for CO is 50 parts per million (ppm) and the TLV for NO2 is 5 ppm and is noted as a “ceiling limit” which cannot be exceeded for any amount of time. Since the nameplate air quantity is the quantity of air necessary to dilute the engine exhaust to the TLV limit, it is imperative that this minimum air quantity be provided where the unit of diesel equipment is operating so as to ensure miners are not exposed to hazardous concentrations of CO and NO2. It should be noted that the testing of the diesel engine to determine the nameplate air quantity is performed on a new engine set to the manufacturer’s specifications which represents the best operation of the engine. 75.327 Air Courses and Trolley Haulage Systems The air in the trolley haulage entry, when separated from the belt haulage entry, may be used to ventilate the active working places. Should conditions develop that necessitate an increased velocity in trolley haulageways in excess of 250 feet per minute, the mine operator should apply to the district manager for an exception through the ventilation plan, Section 75.371(v), giving in detail the reason for the request. 75.330 Face Ventilation Control Devices The "area of deepest penetration" referred to in Section 75.330(b)(2), in conventional mining sections, is considered to be the solid surface of the coalbed at the advancing end of the working place, in both uncut and undercut faces prior to blasting. After blasting, the "area of deepest penetration" is the toe of the coal fall before loading starts, and advances with the toe as the fall is loaded. 75.340 Underground Electrical Installations Underground electrical installations shall be considered to be in a noncombustible structure if the enclosure provides protection against flame spread for at least 1 hour when subjected to a fire test incorporating an ASTM E119-88 time/temperature heat input or equivalent. The following types of installations, if acceptable prior to November 16, 1992, will be accepted as meeting the requirements for a noncombustible structure required by 75.340: January 2013 (Release V-45) 42
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