Page 351 - Reciprocating Compressors Operation Maintenance
P. 351
336 Reciprocating Compressors: Operation and Maintenance
Symptom: A recently overhauled, horizontal two-stage compressor
developed a noisy suction valve.
Problem: The gasket under the suction valve had been left out making it
loose on the seat.
Question: When intercooler pressure indicates a leaky or broken com-
pressor valve, how do you tell which one is defective without remov-
ing all valves?
Answer: Leaking valves can be detected by cover temperatures that are
somewhat greater than others, or by a slight difference in valve operat-
ing sound, or by both of these symptoms.
Question: How can the discharge temperature indicate the compressor
mechanical condition?
Answer: A compressor, operating under the same air pressure and cool-
ing water temperature, should register constant discharge air tempera-
ture. If the latter increases while the other conditions remain constant,
leakage is definitely indicated, usually of the hot discharge back to an
intermediate pressure. It may be either valve or piston ring leakage. A
plant log recording interstage pressures and temperatures should be
regular practice, because it definitely notifies the operator when to
examine piston rings and valves. An increase in discharge temperature
also puts him on guard concerning the mechanical condition of a sin-
gle-stage compressor.
Question: What causes discharge air temperature to increase gradually
and the cylinder to become somewhat hotter than formerly, when pis-
ton rings and valves are in first-class condition and jacket water tem-
perature is normal?
Answer: After years of operation, if jacket water quality is not particular-
ly good, the jacket cooling effects may have deteriorated considerably.
The inside of jacket walls may be covered with heavy deposits of lime
or magnesium, which interferes with normal heat transfer. The answer
of course, is to thoroughly clean the jacket.
SERVICE CONDITION CHANGES
A change in suction or discharge pressure may cause problems.
Observing these pressures should be part of any troubleshooting effort.
A plant operator advised that he had purchased a 12 x 9 single-stage
horizontal compressor and that he was using it for 100 psi pressure. He
inquired about the working conditions for which this machine was suit-