Determination of electrical clearances for permissible equipment operating in gassy mines and tunnels

A design algorithm is derived for calculating the minimum allowable electrical clearances in alternating and direct current "permissible" equipment, which are authorized to operate in gassy mines and tunnels under Part 18 of Title 30, Code of Federal Regulations. The calculated clearances apply to operations at altitudes ranging up to 12000 ft (3658 m) above sea level. The minimum allowable clearance values are tabulated for typical nominal mining machine voltages and maximum operating temperatures within explosion-proof enclosures. An equation is provided for increasing the clearances when the listed maximum temperatures are exceeded.<
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