IV.VERY HIGH-PRESSURE COMPRESSORS.
B. High-Duty Apparatus.
1. Machines.-The Hurcourt compressor (Fig. 156) is used in Paris for compressing gas, at a pressure of 11 atmospheres, into cylinders holding 247.1 cubic feet each.
The apparatus consists of two single-acting pumps, disposed on
each side of a pyramidal support, which carries at its summit
a shaft with cranks at right angles, and a belt-pulley be. tween
the two standards. The cylinder is of cast-iron, with no exterior
envelope, and no means of refrigeration. At the base is a tube,
in which is the conical inlet-valve. Opening into the piston
is a conical valve which communicates by three openings leading
throgh the rod, and just above the piston-packing, with the annular
space between red and cylinder. The piston, on descending, compresses
the gas contained in the pump-body, until a pressure is reached
sufficient to enable the gas to lift the valve in the piston and
pass into the annular space above. On the up-stroke of the pump
the gas is again compressed, and at the same time a new supply
is drawn in through the valve in the cylinder-bottom. Dimensions
and data: Absolute air-pressure, 11 atmospheres; volume of compressed
gas furnished at this pressure by the two pumps, 2,939.7 cubic
feet. Motor, horizontal non-condensing engine-no steam expansion-connects
with 6 compressors by belting. Diameter of piston, 13.26 inches;
stroke, 24.9 inches; steam-pressure, 6 atmospheres; revolutions
per minute, 70. Compressor: Diameter of piston, 7.02 inches;
stroke, 23.4 inches; useful volume of cylinder, 638.6 cubic feet;
revolutions per minute, 30; theoretic volume generated at this
velocity by each compressor, 32,337.6 cubic feet.