Page 398 - Reciprocating Compressors Operation Maintenance

Safety in Operation and Maintenance 383

1. Before attempting any maintenance, be certain the compressor can-
not be started accidentally. Tag the switch and then pull the fuses or
disconnects.
2. Blow down the receiver and all intercoolers and aftercoolers. Isolate
the compressor. Tag the shutoff valve.
3. Be certain there is no pressure in the machine before opening.
Loosen, but do not remove, all nuts on a discharge valve cover. Pry
it loose so that any trapped air may escape; then remove all nuts and
the cover.
4. Place a wooden block in the cylinder between the piston and each
head to prevent its movement. Do this through a valve hole. Some-
times it may be more convenient to block the crosshead in the frame.
5. Always use a safety solvent for cleaning compressor parts and dry
them thoroughly before replacing.
6. Pop safety valves manually at least once a week.
7. If a safety valve blows during operation, stop the unit immediately
and determine the cause. Safety valves on the receiver will normally
blow only if the capacity control is not functioning correctly. An
intercooler safety valve will blow when there is unusual leakage in
the higher-pressure stage. Any blowing safety valve indicates trou-
ble somewhere.
8. Read the instruction book.
9. Review safety precautions as shown in Figure 7-2.

Am PIPING

More and more compressed air piping systems are being installed using
plastic pipe. Plant engineers recognize the advantages of specifying plas-
tic pipe. It is easier to fabricate, install, and maintain than metal. But, plas-
tic pipe must be carefully selected when intended for air pressure system.
Most plastic pipe is limited to pressures below 150 psi and tempera-
tures below 200°F to 300°F. The pipe used for plant compressed air dis-
tribution is ABS (acylonitrile butadiene styrene copolymer). It can handle
air pressure to 185 psi at ambient temperature. Because it cannot rust, it
does not contaminate wet compressed air with corrosion products.
However, some type of lubricating oil used in compressors can attack
ABS pipe. ABS is especially sensitive to many synthetic oils; therefore,