Page 468 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Lube, Seal and Control Oil System Best Practices Best Practice 7 .32
It is very important to note that the trip valve will only close if All turbine trip valves should be provided with manual ex-
the spring has sufficient force to overcome valve stem friction. ercisers to allow this feature. Figure 7.32.6 presents facts
Steam system solid build-up, which increases with system concerning manually exercising a turbine while on line.
pressure (when steam systems are not properly maintained), can Protection system philosophies have tended to vary geo-
prevent the trip valve from closing. graphically with steam turbine vendors, as indicated in
To ensure the trip valve stem is free to move, all trip valves Figure 7.32.7.
should be manually exercised on-line. The recommended fre-
quency is once per month.

Fig 7.32.2 Typical steam turbine protection (Courtesy of Elliott Co.)

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