Page 410 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Best Practice 7 .10
Lube, Seal and Control Oil System Best Practices Best Practice 7 .11
space is minimal, major components can be arranged such that Reservoir integral with component
accessibility is possible.
Refer to Figure 7.9.10. This arrangement is frequently used
in restricted space locations, or could be the result of an
Horizontal console (no components on the attempt by the original equipment vendor to minimize cost.
reservoir) Careful scrutiny of arrangement design early during the
Please refer to Figure 7.9.9. This console arrangement is fairly project can avoid problems. Note from the figure that even
typical of a critical equipment lubrication system. Note that the though all components are mounted on the reservoir, ac-
positions of components afford ample space for maintenance cessibility is maximized to components. In this case, the
and equipment calibration. In addition, note the placement of reservoir was mounted approximately three feet below grade,
interconnecting piping, thus allowing for maximum mobility on thus allowing all components to be within easy maintenance
the console. reach.

Best Practice 7.10Practice 7.10
Best

If the main oil pump driver must be single stage steam The above best practices will ensure optimum main oil pump driver
turbine observe the following best practices for maximum reliability and result in a serviced unit of 99.7% reliability or greater.
steam turbine reliability:
Lessons Learned
Use an eductor for the steam seal system
Select a control valve actuator with 50% additional force than Steam turbines used for main oil pump drivers have the
required lowest reliability of oil system components and are re-
Do not use hand valves sponsible for most oil system trips.
Install oil condition monitoring bottles at the bottom of each bearing
bracket Benchmarks
Do not use a sentinel valve This best practice has been used since 1990 to produce oil systems of
highest reliability, and has resulted in unit reliabilities above 99.7%.

B.P. 7.10. Supporting Material

See Chapter 5 of this book for Single Stage Steam Turbine Best
Practices (B.P.s 5.14, 5.15, 5.16, and 5.17).

Best Practice 7.11Practice 7.11
Best
Always test oil system relief valves on the oil console and Lessons Learned
not on the PSV test rig to ensure that the settings are not Many unit trips have been traced back to improper setting
lower than specified. of relief valves that caused them to open at lower than set
All oil system relief valves are the modulating type. pressures which required the auxiliary pump to start.
Modulating type relief valves start to open at the specified set point Starting of the auxiliary pump was either too late or caused
but require additional pressure (‘accumulation’) to open fully. control valve instability resulting in a low oil pressure trip
PSV test rigs are set up for ‘poppet’ type relief valves that open fully
at their set point. and a unit trip.
Frequently, oil system relief valve set points are set erroneously for
their full open set point on the PSV test rig which results in their Benchmarks
opening prematurely when re-installed on the oil console. This best practice has been used since the early 1980s when com-
Using a calibrated pressure gauge, and testing the relief valves on missioning a large petrochemical plant. Since that time, implementing
the oil console saves time and ensures the proper setting. this best practice has resulted in plant oil system and unit reliabilities
above 99.7%.

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