compressor. Mechanical seals serve to keep the
second-stage cylinder are arranged in-line in in-
oil isolated from the compression chamber.
dividual blocks mounted to the crankcase (frame)
with a distance piece (frame extension). The
RECIPROCATING TYPE.--All recipro-
crankcase is mounted on a subbase that supports
cating air compressors are similar to each other
the motor, moisture separators, and a rack
in design and operation. The following discussion
assembly. The intercooler, aftercooler, freshwater
describes the basic components and principles of
heat exchanger, and freshwater pump are
operation of a low-pressure reciprocating air
mounted on the rack assembly. The subbase serves
compressor.
as the oil sump. Figure 7-23 shows the general ar-
The LPAC is a vertical, two-stage, single-
rangement of the reciprocating-type compressor.
acting compressor that is belt-driven by an
The compressor is of the crosshead design.
electrical motor. Two first-stage cylinders and one
Figure 7-24 shows cross-sectional views of
Figure 7-24.--L.PAC, cross-sectional views (reciprocating type).
7-21