Page 326 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Steam Turbine Best Practices Best Practice 5 .12

Fig 5.12.3 Overspeed detection (Courtesy of Elliott Co.)

To ensure the trip valve stem is free to move, all trip valves
should be manually exercised on-line. The recommended
frequency is once per month for High Pressure (40 bar)
Loss of control oil pressure
Spring force automatically overcomes oil force holding valve open steam systems and daily for very high pressure (1000 bar D)
(approximate set point 50–65% of normal control oil pressure) steam systems.
Manual trip (panic button) All turbine trip valves should be provided with manual ex-
Manually dumps control oil on command ercisers to allow this feature. Figure 5.12.6 presents facts
Optional
concerning manually exercising a turbine while on line.
Turbine excessive axial movement
Protection system philosophies have tended to vary geo-
graphically with steam turbine vendors. Figure 5.12.7 presents
Fig 5.12.4 Internal protection these facts.

299