Page 138 - Reciprocating Compressors Operation Maintenance

1 24 Reciprocating Compressors: Operation and Maintenance

Contamination Concerns

Dirt and air are the two primary factors involved in most lube systems
failures. The lubrication system is a hydraulic system, and like any other
system of this type, dirt in the oil can cause serious damage to lubrication
system components. Even if it does not cause immediate failure, it can
greatly reduce the reliability of the lube system and compressor. Proper
filtration and clean oil are necessities.

Purging Oil Lines and Components

Although not usually the cause of damage in a lubrication system, the
presence of air in lube lines and components is often the cause of lubrica-
tion failure. Finding where it lies is often difficult, and eliminating its
source can also be tricky. Remember, although air cannot usually damage
the components of a lube system, it certainly does not lubricate the com-
pressor very well, so all air must be eliminated.
Purging of air in lube systems after installation, maintenance, or test-
ing is very important. The proper purge method is to begin at the source
and move progressively downstream, verifying at the inlet and outlet of
each component that all air and contaminants have been eliminated.
When new tubing is run, care should be taken to avoid pumping dirt,
particles of cut tubing, or other contaminants into the components. These
can be very damaging.
Pump a large quantity of oil through long tubing runs before connecting
them. A large displacement portable hand pump works well for this purpose.

Terminal Check Valves

The final, and certainly an important part of a lubrication system, is the
terminal check valve. It must hold against back pressure, preventing
backflow of gas or air in the oil line during shutdown. If it does not, gas
can work back into tubing and cause air-lock problems. Therefore, a
check valve must be located at the end of every oil line.
Double ball checks should be used on all compressor and packing
feeds, preferably the "soft ball" or "soft seat" type, capable of positive
sealing under adverse conditions. Mount the check valves horizontally or
discharging up. Maintaining a wet seat aids in positive sealing.