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112 Gas Turbine Handbook: Principles and Practices
Rotor Speed
Figure 7-4. Rotor speed is a control function biased by temperature.
Three measurement methods are commonly used to monitor oil
temperature: oil throw-off temperature from the bearing, immersed oil
temperature (actual oil temperature), and bearing metal temperature.
Since, the object of measuring oil temperatures is to determine the bearing
metal temperature, that is the most direct method to use. This usually
implies contact thermocouples or resistance temperature detectors,
commonly referred to as RTD’s. RTD’s are accurate in low temperature
applications up to 500°F. RTD’s are used in measuring throw-off or immersion
oil temperature. The other significance of oil temperature is determining
cooler capacity, cooler efficiency and seal leaks, i.e., hot gases
leaking into the oil.