Page 493 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 7 .37
Be st Practice 7 .38 Lube, Seal and Control Oil System Best Practices

Best
Best Practice 7.37Practice 7.37
Require separate drains with sight glass and TI in each instruments in the drain lines has led to un-scheduled plant
atmospheric seal drain line, to enable the monitoring of the shutdowns and gas releases when excessive atmospheric
atmospheric seal condition and ensure seal maintenance seal wear went undetected.
is only performed during a scheduled turnaround.
Failure to monitor atmospheric seal flow (by visual means) and Benchmarks
temperature during start-up when atmospheric seal oil pressure may This best practice has been used since the late 1960s to ensure that
be low, or during upsets will expose the plant to unscheduled shut- the atmospheric seal could be monitored during operation, and to
downs and possible gas releases to the plant environment. provide valuable information to the turnaround planning team to rele-
gate the required seal change out to a planned turnaround.
Lessons Learned
Failure to require a separate drain for each atmospheric
seal and to install sight glasses and temperature

B.P. 7.37. Supporting Material

See B.P: 7.34 for supporting material.

Best
Best
Best Practice 7.38Practice 7.38Practice 7.38Practice 7.38
Best
Require that the seal oil system is on before gas is in- Lessons Learned
troduced to the compressor case for bushing seals to Introducing gas into the compressor before the seal oil
prevent a gas release to the plant. system is commissioned will cause a gas release into the
Lack of design information disclosed to plant operation personnel plant which can be life threatening if the gas is sour, and
and/or those responsible for writing the plant operating procedures has will drastically reduce seal MTBF.
led to the false belief that starting the oil system prior to introducing gas
I have been in plants where sour gas bushing seal applications,
into the compressor will flood the compressor with seal oil.
without sweet buffer gas, allowed process gas to be introduced into
All compressor vendors design their units with shaft steps or other
the compressor before the seal oil system was put into operation.
means to greatly minimize the entrance of oil into the compressor.
Since the only means to prevent entrance of process gas into Benchmarks
a bushing seal is a positive seal oil to seal gas pressure differential, This best practice has been used since the mid-1980s when a plant
failure to commission the seal oil system prior to admitting process gas had a history of bushing seal low MTBFs (less than 12 months), be-
into the compressor will:
cause gas was introduced into the compressor before the oil system
Result in a gas release to the plant environment was commissioned and the operating procedure was written to allow
Trap any debris in the process gas stream into the inner bushing this practice. Since that time, this best practice has been used to
seal thus failing the seal and possibly distributing debris through the ensure optimum bushing seal MTBFs (in excess of 100 months).
seal oil system up to the outside of the filter cartridge.

B.P. 7.38. Supporting Material
See B.P: 7.34 for supporting material.

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