Page 313 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 5 .11 Steam Turbine Best Practices
discussed later in this chapter. In addition to the two major - Temperature
protection systems mentioned above, other typical protection - Surge
systems for a rotating equipment train are: - Speed

- Shaft vibration As an example, refer to Figure 5.11.4 e a speed controller
- Bearing bracket vibration that may be familiar.
- Axial thrust displacement In Figure 5.11.4, we compare an auto ‘cruise control’ to
- Bearing temperature a steam turbine governor (typical single stage mechanical/hy-
- Process gas temperature draulic). Both are speed controllers and have an:
- Lube oil pressure
- Input
- Seal oil DP - Set point
- Suction drum high liquid level (compressors)
- Output
The table below shows a comparison of these parameters.
Control
Parameter C.C. (Cruise control) T.G. (Turbine governor)
A turbine governor is a speed controller. Important facts
concerning expansion turbine governors are shown in Input Actual speed from Actual speed from speed
Figure 5.11.3. speedometer pick-up
Regardless of type, all controllers have three identical Set point Selected by driver Selected by operator
parameters: Output To fuel control system To steam throttle valve
- Input Figure5.11.5is a schematicofa steam turbine governor system.
- Set point Note that the set point can either be a manual set point, similar
- Output
to a driver setting a “speed” in a cruise control system or a process
variable. Examples of process variable set points would be:
Some familiar controllers are:
- Pressure - Pressure
- Flow - Flow
- Level - Level (pump applications)

Fig 5.11.5 Steam turbine control (Courtesy of M.E. Crane, Consultant)

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