Surface Mine Fans

1. Access to the mine fan equipment shall be restricted by a protective fence or building.
2. Fans shall be operated from a separate power circuit.
   1. Fan motors or transformers for fan motors cannot be energized from the secondary or load side of transformers that supply power to underground mine power systems.
   2. Fan motors or transformers for fan motors may be energized from primary power lines that supply power to transformers for underground mine power systems.
   3. Generators may be used as a power source. If used, a transfer switch shall not be made or broken under load, unless properly rated to interrupt available fault current.
3. Metallic enclosures of electrical equipment shall be connected by grounding conductors to the premises grounding electrode system. The grounding electrode system shall be connected by the grounding electrode conductor to the system grounded conductor, or system grounding conductor, or both if available. The grounding conductor shall be continuous from the point of service to the equipment served. If the power source ground conductor is not provided, the premises grounding electrode system shall have a measured resistance to earth of four ohms or less.
4. Ungrounded power systems shall be equipped with grounded phase indicators.
5. All wiring and electrical equipment associated with fans shall meet the requirements of the National Electrical Code in effect at the time of installation.
6. Fans shall be equipped with a pressure recording device capable of operating even when power to the fan has been interrupted.
7. Fans shall be equipped with a signal system that will give a warning of interruption to a fan.
   1. Signal system shall be fail-safe.
   2. Signal system shall include a minimum of two independent methods of monitoring fan operation; each capable of initiating the warning.
      1. As a result of abnormal ventilation
      2. As a result of loss of power to the fan motor.
   3. The warning shall include an alarm that can always be seen or heard by a responsible person at the mine while anyone is underground in the mine.
   4. The responsible person at the mine shall have two-way communication into the mine.
   5. When the signal system fails or is otherwise not provided, an attendant shall be constantly on duty at the fan while anyone is underground in the mine. The attendant shall have two-way communication with the responsible person at the mine.
8. Fans shall be protected by one or more weak walls or explosion doors or a combination of weak walls and explosion doors located in direct line with possible explosive forces. Weak walls and explosion doors shall have cross-sectional areas at least equal to that of the entry (shaft) through which the pressure from an explosion underground would be relieved. A weak wall and explosion door combination shall have a total cross-sectional area at least equal to that of the entry (shaft) through which the pressure from an explosion underground would be relieved.
9. Except as provided under paragraph "X", fans shall be equipped with fireproof air ducts and be offset not less than fifteen feet from the nearest side of the mine opening.
   1. All operating parts of the fan and drive system (including the fan wheel and blades, shafts, bearings, pulleys, belts, motor, etc.) that are in the fan duct work shall be located a minimum of fifteen feet from the nearest side of the mine opening.
   2. All parts of the fan and drive system (belts, motors, controllers, recording devices, and record books) that are external to the fan duct work shall be located in a fireproof housing outside of the direct line of explosion forces from the mine. A TENV, TEFC, or explosion-proof metal motor enclosure and a NEMA 4 or explosion-proof metal enclosure are examples of fire-proof housings. If they are also rated for outdoor service, no additional protective housing is required.
10. In lieu of the requirements of Paragraph "IX", fans may be located directly in front of or over a mine opening if all of the following conditions are met:
    1. A pressure relief entry that is in direct line with explosion forces from the mine shall be provided. This entry shall have a cross-sectional area equal to or greater than the area of the fan entry.
    2. The pressure relief entry shall have a weak wall or explosion door in line with the entry and shall have a cross-sectional area equal to or greater than the area of the entry.
    3. The surface opening of the pressure relief entry shall not be less than fifteen feet or more than one hundred feet from the surface opening of the fan entry and from the underground intersection of the fan entry and the pressure relief entry.
    4. The coal or other solid material between the fan entry and the pressure relief entry shall have an area of at least 2,500 square feet.
11. Enclosures of disconnects and circuit breakers shall be appropriately labeled for function and voltage to show which circuits they control, unless identification can be readily made by location.