Page 378 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 7.2
Lube, Seal and Control Oil System Best Practices Be st Practice 7.3

Best
Best Practice 7.2Practice 7.2Practice 7.2
Best
Require that a stainless steel reservoir, vessels and piping un-scheduled shutdowns that resulted in long periods
be used to ensure minimum oil flushing time, optimum of outage for oil flushing, and substantial loss of
machinery component life and machinery reliability. revenue.
Oil flushing time can significantly extend commissioning and turn- Systems that use overhead tanks that are either not stainless
around time, if any oil system components or piping are subject to steel, or have carbon steel components, have reduced the machine
corrosion. component MTBF due to iron sulfide building up in the small clear-
Lube and seal oil overhead tanks that are not stainless steel will ances of the machinery components, which has resulted in premature
reduce bearing, oil seal and or driver control and protection MTBF, since failure.
there cannot be a filter between these tanks and these components.
Replacement of existing non-stainless oil system piping, compo- Benchmarks
nents or the entire system can usually be justified in un-spared critical This best practice has been used for projects and retrofits since 1990,
machinery trains, if the train has experienced one or more shutdowns, producing oil unit trains of the highest reliability and serviced critical
which have required oil flushing prior to restart. machinery.
This best practice has optimized centrifugal compressor train re-
Lessons Learned liability (above 99.7%) and machinery component MTBFs (greater than
Critical (un-spared) equipment trains that do not use all 100 months).
stainless steel piping and components have suffered

B.P. 7.2. Supporting Material stainless steel piping, as well as reservoir and overhead tank
material, while carbon steel slip-on flanges have been acceptable
for lube oil service piping. Experience has shown that in systems
Reservoir, vessel, piping and component containing water, such as water seal systems, stainless steel
material preferences flanges as well as pipes are required, since considerable amount
of rust scale emanates from the flange pipe interface area below
Any reservoir, overhead tank design or material preference the flange gaskets. The subject of the material of the main
should be stated. It is recommended that reservoirs and over- components (filters, coolers, valves, etc.), is a purchaser’s
head tanks be constructed of Austenitic stainless steel, to ensure preference. When one considers the potential damage resulting
minimal penetration of excessive debris into the auxiliary from excessive debris in a system, the additional cost for non-
system. In addition, any preference for piping and synthetic corrosive components can usually be justified. This issue should
materials should be stated. Recent practice has been to require be thoroughly investigated prior to auxiliary system purchase.

Best Practice 7.3Practice 7.3
Best
Specify a minimum of one meter distance between all oil I have experienced critical unit shutdowns of a steam turbine driven
system components to allow operator access, and to op- pump, when the local trip lever was accidentally hit due to limited
timize system reliability. space being available when the personnel were climbing on the con-
sole in the course of normal maintenance activities.
Access to all major components is essential to allow operator in-
tervention to switch over to spared system components without the
risk of unscheduled trips of critical equipment (un-spared). Benchmarks
This best practice has been used since my design days for a major
Lessons Learned machinery vendor (late 1960s) to ensure optimum oil system and
corresponding critical machinery train reliability. This best practice
Consoles that are crowded and do not allow easy access
approach continues from that time to ensure þ 99.7% reliability on all
are often ignored by operators and not fully understood in
critical equipment trains.
terms of system function.

349