II. MEDIUM-PRESSURE COMPRESSORS.
A. Low-duty Apparatis.-
l. Fig. 141 represents a compressor of the Sommeiller type designed
for low duty. The piston-plunger moves in an horizontal pump-body,
while the valves are placed in a vertical chamber connecting with
the pump-cylinder. This column is filled with water, so that
when the piston is at the end of its stroke the water covers the
valve above. As at each impulsion a portion of the water is entrained
by the compressed air, there is placed around the chamber a water-jacket
into which a stream of water constantly enters the liquid passing
through the valve into the compressor at each aspiration. The
dimensions, etc., are as follows: Absolute pressure of air, .5
atmosphere; volume of air furnished per minute 278 cubic feet.
Motor of any type: Compressor single-acting; diameter of compressing
piston, 5.8 inches; stroke, same; useful volume of cylinder, 91
cubic feet; revolutions per minute, 15 ; theoretic volume generated
by the piston at this velocity, 1,403 cubic feet.