European Gas Turbines (EGT) Tempest Engine Fuel Control "Operating Temperature"


Thread Starter


I am retrofitting the fuel and auxiliaries control system for a single shaft EGT Tempest gas turbine driving a synch. generator. Came across a calculated parameter called "operating temperature" and need to know how this value is determined. At first I thought it may simply refer to the gas turbine exhaust temperature measurement, but after a closer look at the existing HMI screens I see it is different. My second thought was that it is an attempt to back-calculate turbine combustion temperature from EGT but it actually looks like a lower value (HMI screen shots are while unit is shutdown). It appears to be 30 degC less than the turbine's average calculated exhaust temperature.

Anyone familiar with this unit (or its modern counterpart the Siemens SGT300) that would be able/willing to explain how this value is determined and what it is mainly used for in the PLC.

Unsure what you mean by '.. back-calculate turbine combustion temperature ..'.

I understand working temperature is measured by several probes at the burners.

What does the HMI screens show?
Thank you for a response!

What I mean by Back-Calc is that on some gas turbine control systems the PLC attempts to calculate the actual temperature in the combustors based upon the Exhaust Gas Temperature measurements since it is not practical to measure the combustion chamber temperature directly due to a few factors. Rather the EGT measurement is used and then a calculation is performed to determine the (higher) temperature in the combustion chamber.

From the HMI screens this does not appear to be what Operating Temperature is measuring as it is actually lower, by 30 degC, from the EGT average temp.

Looks like it is used to signal on the AC Lube Oil Pump and Oil Cooler Fans during the post lubrication sequence following a shutdown if the thermocouples used to measure bearing temperatures are all failed (not available). Apparently the engine temperature is used as a back up reading. But why not just use EGT measurement directly for this (or to say another way: what's with the -30 degC).

Thanks for reading

Martin Andrade


We can support your issues with the SGT300 controls system. We are a specialist turbine service provider focusing purely on the Siemens SGT range of gas turbines, including the SGT100, 200 and 300.

Supporting the engines both on the mechanical side and control systems. We support engines around the world including Europe, US, Africa and Asia. If you still require assistance with this issue please do not hesitate to contact us, my number is +44 (0) 7710 307554.


John Fitzmaurice

Jake, the exhaust temperature is biased by the inlet temperature. Before these turbines were made by siemens they were made by ruston. This is the old Ruston turbine Co turbine inlet temperature control scheme. As the ambient temp goes down compressor efficiency goes up, compressor discharge pressure goes up, expansion through the turbine goes up and so the exhaust is cooler at a given turbine operating temperature. GE uses a compressor discharge pressure transmitter to bias exhaust temperature and control fuel and so turbine inlet temperature. I have some info on the old ruston systems I can share.

Contact me at [email protected]

I have some information on ruston/ siemen turbines to share with you.

John Fitzmaurice