Page 179 - Reciprocating Compressors Operation Maintenance

Operation and Maintenance of Reciprocating Compressors 165

* Springs should be replaced. Do not mix new springs and previous-
ly used springs. All springs in the valve should be replaced.
In the case of conical springs, care should be taken to insert
them into the spring nest with the large diameter resting at the bot-
tom of the spring nest.
• Seats. To ensure high valve efficiency, it is important that the seat
face is flat and free of any traces of wear, thus preventing valve
leakage. If the seat face is damaged in any way, remachine and lap
the areas.
Do not remachine valve seats below the specified minimum
dimension; otherwise, there is danger of breakage. Remachining
has to be extended over the entire seat face, including the entire
center part. When a valve seat surface is remachined, new valve
plates or rings should be used to assure proper sealing.

Assembly of Valves

When assembling the valves, cleanliness is extremely important. Be
sure to have all parts in the proper sequence. Make sure all parts are
properly aligned. Before tightening nuts, press the seat and guard togeth-
er by hand to ensure that the parts are properly aligned.
The lock nuts should be tightened with a torque wrench to the follow-
ing values:

Thread Torque (ft-lbs)
K"-24UNF 15-18
JT-20 26-32
3T-18 65-80
3
/4"~16 129-156
7
/T-14 178-214
1"-12 221-268

After the valve has been assembled, check the sealing element for free
movement. This should be done with a small brass rod that will not dam-
age the element.