Page 151 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Compressor Best Practices Be st Practice 3.4

Fig 3.4.11 HDS off-gas-piston rod and piston (Courtesy of
Dresser Rand)

compounds are used. If non-lubricated service is required, PTFE
materials or other Teflon derivatives are used. Note also the
piston hollowed area for piston weight control. Rider band and
ring life is a function of piston speed, cylinder gas temperature
and cleanliness of the process gas. In many process applications,
a strainer is required upstream of the compressor to prevent
excessive ring wear.
Condition monitoring of rider band and piston ring wear can
be accomplished by measuring and trending the vertical dis-
tance between each piston rod and a fixed point (known as rod
drop). This can be accomplished either by mechanical or
electrical (Bentley Nevada proximity probe) means. Of im- Fig 3.4.13 Lube oil system
portance in piston assembly design is rod loading and rod
reversal.
Rod loading is the stress (tension or compression) in the
piston road and crosshead assembly caused by the 6Pacross

Fig 3.4.12 Pulsation dampeners
(Courtesy of Dresser Rand)

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