Page 431 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 7 .16 Lube, Seal and Control Oil System Best Practices
Reliability considerations internal filter bypass. It is suggested that filter vendors be
Several considerations concerning filters are noted below. contacted for possible retrofits where filter elements are not
A. Filter material e As mentioned above, it is important to stacked in this way. End seals on filter cartridges must be se-
select proper filter material. Experience has shown that some curely locked in place on every cartridge to prevent filtered fluid
filter materials will be shed during operation and thus present bypass. Prior to closing filters a thorough check of all cartridge
a risk of critical equipment component damage. Consideration end seals should be made.
should be given to elements that are impervious to the possi- D. Filter cartridge changeout e Care must be taken
bility of any foreign substance in the auxiliary fluid steam. Orlon during dirty filter disassembly to preclude the possibility of
has proven to be a good substance for filter element material. In entrance of debris into the system. If possible, the bottom head
addition, paper filters should not be used in system that can of the filter should be disconnected and thoroughly cleaned or
contain water (steam turbine units or in high humidity areas). back-flushed to ensure clean fluid only enters critical equip-
Experience has shown that water will cause paper elements to ment. In designing new auxiliary systems the possibility of re-
swell, thus increasing filter pressure drop and giving the ap- movable bottom filter heads should be investigated for easy
pearance of plugged filters. cleaning.
B. Filter high viscosity operation e Attention is drawn again to E. Filter housing filling and venting e Following filter car-
operation of filters at high viscosities (usually during cold start- tridge change out, the filter housing should be immediately
up). Excessive filter differential pressure can lead to its collapse. filled using the system fill line (if furnished), or an external
The system fluid should be preheated (additional reservoir source of clean filtered fluid that meets the auxiliary system
heating or possible cooler heating) prior to system operation if specification. Note that using the system fill line requires care
the fluid is not at the minimum starting temperature recom- to prevent a sudden opening of the fill valve that could cause
mended by the vendor. Many unit trips have been caused by a system pressure upset, which in turn could trip the critical
transferring to a cold filter. Continuously open, orificed vent equipment unit. All fill lines should be provided with
lines, leading back to the reservoir have become a ‘best practice’ properly sized orifices. However, they have been known
in cold climates. to disappear from time to time, or have not been sized to
C. Filter cartridge configuration e The use of filter elements prevent significant system pressure reductions when opened
stacked one high has proven to be very successful in eliminating quickly.

Best Practice 7.16Practice 7.16
Best
Require the FAT (factory acceptance test) for the oil con- Proper supply flow, pressure and temperature
sole to duplicate field conditions as closely as possible and Chart recorder for all transient checks (pump trip and two pump
record response times for transients (main pump trip and operation) and transfer valve check, confirming that oil supply
two pump operation) to ensure optimum oil system field pressure during the transient event does not fall to the trip setting.
reliability.
As a minimum, the following items should be included in the FAT: Lessons Learned
Auto start of the auxiliary pump Failure to completely check all oil system component
Two pump operation functions during the FAT will result in delayed start-up and
Relief valve checks possible lower than anticipated unit reliability for the life of
Bypass (backpressure) valve proper valve position and stability
Transfer valve operation the process unit.
Cooler tube leak check
Filter pressure drop and particle check for bypassing Benchmarks
Accumulator pre-charge and bladder condition (if applicable) This best practice has been followed since the 1970s, and has resulted
Supply valve(s) e proper valve position and stability in oil systems and field unit operation of the highest possible reliability.

B.P. 7.16. Supporting Material objectives of this phase are to confirm the proper arrangement
details and functional operation of the equipment.
Factory testing and inspection
Test agenda
Having properly specified, designed and manufactured the unit,
its proper arrangement and operation must be confirmed. This is The equipment must be thoroughly tested prior to field in-
accomplished during factory testing and inspection. The stallation. The test should confirm the functional operation of all

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