Page 47 - Reciprocating Compressors Operation Maintenance

34 Reciprocating Compressors: Operation and Maintenance

Double-acting compressors are those in which compression takes place
on both sides of the piston, with intake and discharge valves at both
ends of the cylinder.
Single-stage compressors are those in which compression from initial to
final pressure is completed in a single step or stage.
Multi-stage compressors are those in which compression from initial to
final pressure is completed in two or more distinct steps or stages.
Two-stage compressors are those in which compression from initial to
final pressure is completed in two distinct steps or stages.
Portable compressors are those consisting of compressor or driver so
mounted that they may readily be moved as a unit.
Intercoolers are devices for removing the heat of compression of the gas
between consecutive stages of multi-stage compressors.
Aftercoolers are devices for removing the heat of compression from the
gas after the last stage of compression is completed. Aftercoolers are
one of the most effective means of removing the major amount of
moisture from the air, provided they have the capability of cooling the
air down to less than 100°F.
Moisture separators are devices for removing moisture precipitated from
gas during the process of cooling, allowing the condensate to collect
and then drain via either a manual or an automatic condensate trap.
Air receivers are pressure vessels that must be built in accordance with
the ASME code. Air receivers take the discharge of a compressor (or
compressors) piped into them, preferably after the air has been cooled,
for the purpose of storing the air and simultaneously reducing the rate
of pressure fluctuation in the air system. This will reduce the frequen-
cy at which the compressor will either load or unload, or start and
stop, as the case may be.

COMPRESSOR TYPE SELECTIONS

Before choosing a specific type of compressor, consideration must be
given to a number of important factors.