Vibrations
in Reciprocating Machinery and Piping Systems
J. C. Wachel/J. D. Tison, 23rd Turbomachinery Symposium,
Texas A&M University, September 13-15, 1994 .
A wide variety of vibration and failure problems occur in reciprocating
machinery and piping systems. Excessive piping vibration problems
usually occur when a mechanical natural frequency of the piping
system or compressor manifold system is excited by a pulsation or
mechanical excitation source. Since reciprocating compressors and
pumps generate high pulsation levels at numerous harmonics, which
in turn produce shaking forces, vibration and failure problems in
these systems are common. Other problems, not associated with the
piping, can be encountered with the compressor/engine frame foundation
and anchoring systems. These can lead to failures of the bearings
and crankshaft. In addition, special problems can occur due to the
torsional natural frequencies and the high harmonic torques, due
to the compressor loading.
Whenever high
vibrations are encountered in reciprocating compressors, pumps
and/or piping, it is necessary to determine if the vibrations
and dynamic stresses are acceptable. Criteria to judge the acceptability
of the vibrations are presented in this paper, along with troubleshooting
methods to determine if the problems are caused by pulsation or
mechanical resonances. The basic principles of pulsation generation
and control are presented. The key to designing and operating
safe piping systems is to control the pulsation levels and separate
the mechanical natural frequencies from the pulsation excitation
frequencies.
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