Page 452 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Best Practice 7 .25
Lube, Seal and Control Oil System Best Practices Best Practice 7 .26

Best
Best Practice 7.25Practice 7.25
Monitor control valve position in all oil systems to determine Lessons Learned
component wear (rotary pumps, bearings and seals) to Failure to mark and monitor control valve stem position in
ensure corrective action is taken during a turnaround. oil systems has led to many surprises and replacements
Marking the position of control valves (marking the stem and valve soon after a turnaround. Monitoring of valve stem position
yoke with a straight edge) at the beginning of a run will give an instant would have identified worn components and allowed re-
indication of component wear for the following items:
placement during a turnaround.
Rotary pumps (screw or gear) e if the bypass valve is closing over
Remember that turnaround action does not affect product revenue,
time.
unplanned action does!
Bearing wear e if the lube oil supply valve is opening over time.
Replacement of an oil pump can take two days considering
Control component wear e if the control oil supply valve is opening
alignment.
over time.
Replacement of a bearing or seal can take three to five days!
Seal wear e if the seal oil supply valve is opening over time.
Check the position of all marked control valves prior to the turn- Benchmarks
around meeting to determine if the affected components need re- This best practice has been used since the late 1980s during all field
placement during the turnaround. visits. This practice has saved many millions of USD by moving
component replacement to the ‘turnaround revenue loss fee zone’!

B.P. 7.25. Supporting Material

Please refer to material in B.P: 7.13.

Best
Best Practice 7.26Practice 7.26Practice 7.26
Best
Check system transient functions (pump transfer) imme- Performing the transient check just prior to the turnaround will allow
diately before turnaround. ample time for any corrective action.
We recommend that the following procedure be followed immedi-
ately before each scheduled shutdown of critical (un-spared) ma- Lessons Learned
chinery units: In many cases, oil system functional checks during a turn-
1. Confirm that the auxiliary oil pump start switch actuates at the around confirm that the transient function of the system is
proper setting and starts the auxiliary oil pump. acceptable, only to find after the turnaround that a unit trip
2. Put the auxiliary oil pump into auto start mode, and station an has occurred during a transient event.
operator at auxiliary oil pump with instructions to immediately As mentioned above, the amount of oil taken by the machinery
manually start auxiliary oil pump if compressor unit trips. components during operation is more than during the stationary unit
3. Trip the main oil pump and observe the following (with strip charts, case (when the unit is not operating).
if possible): The only way to accurately confirm oil console transient response is
A. Auxiliary oil pump starts without unit trip while the unit is in operation.
B. Lowest tube oil pressure during transient The only way to avoid exposure to a unit trip during plant operation
C. Lowest control oil pressure during transient is to perform the transient test immediately prior to a planned
D. That all control valves remain stable shutdown.
The above procedure is the only way to ensure that the transient
response of the oil system will not cause a trip during operation. Benchmarks
The amount of oil taken by the machinery components during op- This best practice has been employed since 1990 to accurately check
eration is more than during the stationary unit case (when the unit is not the transient response of critical machinery oil systems prior to
operating). a planned shutdown and to define an action plan for corrective action if
Most functional oil system checks are performed at turnarounds required.
with the unit off-line, only to find during operation that the system
cannot respond to a transient event without a unit trip.

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