of the rod and the crank pin bearing boxes; (2)
by adding or removing shims between piston and
socket type wrist pin boxes; (3) by screwing in or
backing out the wrist pin adapter, in compressors
having a threaded wrist pin adapter; (4) by turn-
ing the piston rod in or out of the cross head, in
double-acting pistons equipped with piston rod
and cross head. In some compressors, the piston
clearance is nonadjustable.
Because of the great variety of control,
regulating, and unloading devices used with com-
pressors, detailed instructions on their adjustment
and maintenance must be obtained from
manufacturers technical manuals.
When a control valve fails to work properly,
disassembly and a thorough cleaning is usually
necessary. Some control valves are fitted with
filters filled with sponge or woolen yarn, to pre-
vent dust and grit from being carried into the valve
chamber and to remove gummy deposits which
come from the oil used in the compressor
cylinders. Replace the filter element with the
specified material each time a valve is cleaned.
WARNING: DO NOT use cotton as a filter
element because it will pack down and stop the
Since relief valves are essential for the safe
operation of a compressed air system, they must
be kept in satisfactory working condition at all
times. Relief valves should be set as specified by
the manufacturer, and tested by hand each time
the compressor is started. Periodically, the set-
ting of relief valves should be checked by raising
the pressure in the space which they serve.
Lubricating and Cooling Systems
The maintenance procedures for lubricating
and cooling systems in air compressors are similar
to the procedures used for lubricating and cool-
ing systems in internal combustion engines. For
air-cooled compressors, steps must be taken to
keep the cooling fins clean. Oil and dust act as
insulators and, if allowed to collect on the fins,
will prevent heat transfer.
In general, the lubricating system of a com-
pressor will give you little trouble if the follow-
ing steps are taken:
1. Keep the reservoir oil at the prescribed level
in order to maintain proper oil temperature.
2. Change crankcase oil periodically, flush the
crankcase, and clean the oil filter.
3. Maintain proper lube oil pressure by keep-
ing the oil pump in good working condition and
by adjusting the bypass relief valve.
4. Keep the oil cooler free from leaks to pre-
vent oil contamination and emulsification.
5. Inspect cylinder lubricators.
a. When Navy Symbol 9000 series oil is
used for compressor cylinder lubrication, the sight
flow indicators should be filled with glycerine
b. When Navy Symbol 2000 series oil is
used for cylinder lubrication, the sight flow in-
dicators should be filled with a mixture of 50%
distilled water and 50% glycerine.
6. Keep the lubricator in proper adjustment
for the specified quantity of oil feed.
The general requirements for care and
maintenance of compressor cooling systems are
1. Intercoolers and aftercoolers should be in-
2. Collections of gummy oils or tarry
substances on the sides of cooler tubes should be
removed by washing the tube nests with a cutting
solution. Be sure that the nests are completely dry
3. Any leaks in tube nests must be repaired;
otherwise, water will leak into the compressor
while it is secured, and air will leak into the water
side during operation.
If during operation, a water relief valve on the
coolers blows while the cooling water pressure is
normal, it is evident that a tube in the cooler is
ruptured. The compressor should be secured im-
mediately and the tube plugged, if possible.
4. Cylinder water jackets should be inspected
and cleaned periodically with a cleaning nozzle.
ENGINEMAN 1 & C