Page 230 - Reciprocating Compressors Operation Maintenance

Operation and Maintenance of Reciprocating Compressors 215

Intercoolers - GPM* = BHP/4 (base 20°F rise)
Aftercoolers - GPM* = BHP/6 (base 30°F rise)
* Multistage Machine—use BHP of last cylinder
3. Water quantity should maintain discharge temperature well below
400°F, preferably 300°F.
4. Inlet water temperature to the cylinder jackets should never be less
than that of incoming gas temperature.
Jacket water temperatures should be 15°F to 20°F above the
incoming gas temperatures to prevent condensation.
5. Cooling water should be shut off when unit is shut down. Remem-
ber that condensation may occur on cylinder walls whenever wall
temperatures drop below gas temperatures.
CAUTION: Do not start compressor without turning on cooling
water.

MAINTENANCE

The amount of maintenance required by a closed system is very small
relative to other types of systems. If the cooling system is stretched to its
limits, the maintenance requirements may increase. Frequent cleaning of
the heat exchanger and replacement of the coolant with one having better
heat removing capacity may be required.
Obviously, system components such as pump impellers, pump seals,
and thermostatic elements need periodic maintenance or replacement, but
typical time intervals should be years, not weeks or months.

NON-LUBRICATED COMPRESSOR MAINTENANCE

Chapter 2 showed how the design of the non-lubricated or oil-free
compressors differs from the more conventional cylinder-lubricated com-
pressor. The design should make oil-free compressors reliable and give
trouble-free operation. However, these machines are likely to require
more frequent maintenance than lubricated compressors if they are to
give dependable long-term service.
It is important to understand the basic difference between lubricated
and conventional non-lubricated cylinders. In reciprocating compressors,
pistons work against pressure and must have a sliding seal to allow the
piston to compress the gas without leakage past the piston. The piston
rings provide this sealing. Rings are made with "spring," which tends to