Section 43.71. Compressor plants

(a) A good and sufficient compressor plant for the compression of air shall be provided to meet not only ordinary conditions, but emergencies, and to provide margin for repairs at all times. Provision shall be made for storing in tanks at each boiler house enough feed water to last 12 hours, unless connection is made with two independent and separately sufficient sources of supply.

(b) The plant shall be capable of furnishing to each working chamber a sufficient air supply for all pressure to enable work to be done as nearly as possible in the dry.

(c) When electric power is used for running compressors supplying air for compressed air tunnel work, there shall be compliance with the following:

(1) There shall be two or more sources of power from the power stations to the compressor plant. The power feeders shall each have a capacity large enough to carry the entire compressor plant load and normal overload. The feeders should preferably run from separate generating plants of substations and be carried to the compressor plant over separate routes and not through the same duct lines and manholes, so that the breakdown of one feeder should not cause an interruption on the other feeder.

(2) There shall be duplicate feeder bus bars, and feeder connections to the bus bars shall be so that either feeder can feed to each separate bus-bar set, individually, or simultaneously to both sets.

(3) There shall be at least two compressors so connected to the bus bars that they may be operated from either set of busses. The compressors shall be fed from different bus bar sets, that a breakdown of a feeder or bus bar would interrupt the operation of only part of the compressor plant.

(4) Duplicate air feed pipes shall be provided from the compressor plant to a point beyond the lock.