Page 172 - Reciprocating Compressors Operation Maintenance

158 Reciprocating Compressors: Operation and Maintenance

gas flow does not impact the closed valve evenly around its perimeter;
thus, the wobbling opening and closing motion results.
Uneven impact can also cause multi-ring valves to open unsynchro-
nized, one ring opening first and taking the most severe impact, and the
others following the lesser impacts against the stop plate. Such a pattern
will cause one ring of the set to fracture more frequently than the others,

VALVE PROBLEMS

Experience has shown that after the "shakedown" or initial commis-
sioning of a new compressor installation, very few valve problems occur
and the compressor operates trouble-free.
Valve problems start to become more frequent after a period of six or
seven years of operation and are due to normal wear. If improper recon-
ditioning and rebuilding is then performed, these problems become fre-
quent and cause continuing unscheduled shutdowns.
Invariably the valves are condemned and valves of a different type or
manufacture are purchased and installed. The valve troubles now disap-
pear, not because of the different style valve or manufacturer, but simply
because new valves have been installed.
The same results might have been obtained at considerably lower cost
if the original valve had been properly maintained and properly recon-
ditioned.
Again, keep in mind that improper maintenance is the major cause of
valve failures. Valves are often rebuilt with parts that have not been
reworked and restored to the original manufacturer's tolerances or have
been machined with no regard to flatness, finish, or hardness effects.

Record Keeping

Experience has also shown that a systematic study of valve problems
will provide the best and often the quickest solutions to valve problems.
Record keeping is necessary to successfully evaluate and solve valve
problems. It is obvious that records should be sufficiently detailed to
show which parts are involved and where these parts were located in the
compressor. A picture of some sort is helpful in spotting a pattern of
valve failure. A typical valve location chart is shown in Figure 3-20.