Page 24 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

List of Lessons Learned
6.2: Failure to consider actual site conditions has resulted in 7.19: Failure to condition monitor oil reservoirs and rundown
power deficient gas turbines. tanks causes failures.
6.3: The majority of mechanical drive gas turbines produce 7.20: Cool oil in the non-operating cooler or filter can cause
insufficient site power. unit trips on low oil pressure.
6.4: Failure to use experienced gas turbine systems has led 7.21: Excessive unit trips lower the reliability of critical
to significant start-up delays. machines.
6.5: Lemon bore or offset sleeve bearings have extended 7.22: Plants frequently experience unit trips caused by
FAT periods. control valve issues.
6.6: Modular change-out agreements can significantly 7.23: There have been explosions and fires from excessive gas
reduce downtime for repair. in the oil reservoir.
6.7: An inadequately sized inlet air filter will reduce turbine 7.24: Many plants have low machine reliability due to old
power. instrument malfunction.
6.8: Carbon steel lube systems extend oil flush times and 7.25: Failure to mark and monitor control valve stem position
expose bearings to failure. has led to many surprises.
6.9: Failure to trend performance does not allow 7.26: Oil system functional checks during shutdown do not
maintenance cycles to be extended. confirm transient functions.
6.10: Efficiency calculations will be erroneous when 7.27: Always evaluate oil system reliability issues in terms of
torquemeters are not installed. lost revenue costs.
7.28: Improper sizing of interconnecting oil piping has caused
reliability and safety issues.
Chapter 7 Lube, Seal and Control Oil 7.29: Not tracing oil system piping in the field has led to many
oil system failures.
System Lessons Learned 7.30: Failure to detect initial condition change has caused
long shutdown periods.
7.1: Conditions and oil grades other than those specified will 7.31: Failure to check the accumulator condition has resulted
affect system reliability. in many unit trips.
7.2: Critical trains with carbon steel systems have suffered 7.32: Malfunctioning solenoid valve trip systems have
un-scheduled shutdowns.
resulted in turbine failures.
7.3: Consoles that do not allow easy personnel access reduce 7.33: Failure to periodically exercise turbine trip valves has
system reliability.
caused catastrophic damage.
7.4: Not filling console baseplates with cement will affect 7.34: Insufficient oil seal atmospheric bushing cooling has
component reliability.
resulted in low seal MTBFs.
7.5: Failure to design audit oil systems has caused many 7.35: The MTBF of dynamic bushing inner oil seals is less than
start-up delays and trips. straight bushing seals.
7.6: Failure to prevent infiltration of oil into refrigeration 7.36: Failure to use a sweet and clean buffer gas has resulted
systems will result in large decreases in plant capacity. in low seal MTBFs.
7.7: Not using centrifugal pumps in oil systems reduces 7.37: Failure to install sight glasses in the atmospheric drain
system reliability. lines has led to gas releases.
7.8: Failure to detect rotary pump strainer blockage has 7.38: Introducing gas into a bushing seal prior to seal oil
resulted in excessive pump wear. operation will cause a gas release.
7.9: Steam turbine main pump drivers have the lowest 7.39: An atmospheric bushing operating on low reference gas
reliability of any oil pump driver. pressure will overheat.
7.10: Steam turbine main oil pump drivers are responsible for 7.40: Many oil seal failures are caused by debris from dirty
most oil system trips. overhead seal oil tanks.
7.11: Many unit trips have been traced back to improper 7.41: Internal float type drainers have been responsible for
setting of relief valves. plant safety issues.
7.12: Critical (un-spared) unit trips have been caused by 7.42: Seal oil entry into the compressor can be the result of
friction-bound relief valves. too small drainer orifices.
7.13: Pneumatic actuated valves response time is less than 7.43: Degassing tanks do not eliminate the entrance of
direct acting control valves. process gas into the oil reservoir.
7.14: Lube oil systems installed without accumulators will
eventually cause unit trips.
7.15: Filters do experience bypassing and expose critical
machines to bearing failures. Chapter 8 Pump Mechanical Seal
7.16: Failure to check all oil system functions during the FAT Flush Lessons Learned
will result in delayed start-up.
7.17: Oil systems not provided with TMR shutdown logic 8.1: Incorrect process conditions on the seal data sheet will
experience lower reliability. lower seal MTBFs.
7.18: Poor oil system field flushes result in significantly 8.2: The use of strainers or cyclones in the flush system will
extended start-up times. lower seal MTBFs.

xxiii