Mark V Gas turbine


Thread Starter


On gas turbine when the diesel engine is separated from the gas turbine during operation, the Accelerating speed is going so slow, and don't reach the synchronize speed, until the exhaust temperature going high, and the turbine tripe, and gives message " Exhaust temperature high, TRIP "

thanks and regards,
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So, I'm presuming the gas turbine is a GE-design Frame 5 or Frame 6 heavy duty gas turbine with a Mark V turbine control system.

When did this problem start? After a maintenance outage? After a trip from load? If it started after a maintenance outage, what work was done during the maintenance outage? In other words, what has changed since the beginning of the problem (or immediately prior to the start of the problem)?

"Stalling" during acceleration is most often caused by things like dirty turbine inlet air filters or wet turbine inlet air filters, and/or dirty IGVs, or dirty axial compressors. Sometimes if any of the above conditions, or some combination of the above conditions, exist(s) then "stalling" can occur. And, in this case I'm referring to "stalling" as the slow-down in acceleration when the gas turbine exhaust temperature reaches the maximum allowable limit during acceleration (which is usually equal to the value of the Control Constant TTKXn_I--the isothermal limit of exhaust temperature). What's happening when any of these conditions are occurring is that the air flow through the unit is not sufficient to allow enough fuel to be burned to allow a uniform speed increase during acceleration.

Another cause which might be the actual cause or a contributor to the cause is insufficient torque being applied by the diesel engine through the torque converter. Either the diesel is "tired" and needs refurbishment, or the torque converter is wearing out and needs refurbishment. Some diesels use hydraulic controls to change diesel speed/torque in response to one or more solenoids being energized/de-energized; others use an electronic means to control the fuel rack in response to an analog signal from the Mark*. While it's not likely, sometimes the fuel control mechanism can require adjustment. Another possible cause for the diesel not providing enough torque could be that the diesel fuel filter(s) are dirty and need to be changed. (Some diesel fuel filters with paper elements can become swollen if there is any water in the diesel fuel, and restrict ("choke") the flow of diesel fuel. This will be most evident if the fuel rack is at or near maximum when the load on the diesel is high.)

Can you tell us when the diesel engine/torque converter is usually de-coupled from the turbine-generator shaft during acceleration (before the stalling/tripping started occurring? And, at what speed is the de-coupling occurring during the stalling/tripping?

Normally, when the Mark* detects the actual exhaust temperature has reached the maximum allowable limit during acceleration it just "freezes" the fuel (FSR)--meaning that it will not allow the fuel flow-rate to increase even though the acceleration rate has decreased below reference.

The exhaust overtemperature trip setpoint is 40 deg F above the maximum allowable exhaust temperature, and unless the fuel control valve is unstable or the fuel supply pressure/flow is unstable the Mark* should be more than capable of preventing an exhaust overtemperature trip by limiting the fuel to limit the exhaust temperature.

Is the fuel supply (natural gas or liquid fuel) stable (pressure and flow-rate) during starting/acceleration?

So, you see there could be one or more factors which can affect the ability of the unit to accelerate without the torque assist from the diesel engine and torque converter.

If you can provide answers to the questions above (all of them--even if you feel the question is not relevant) we can probably provide more help. But, without more information there's not much more we can do. Hopefully, you have been given enough explanation of the possible causes of stalling that might be of help in troubleshooting that problem. The tripping on high exhaust temperature, though, is very unusual and would require lots more information--and actionable data, such as from the Trip History function of the Mark V. (You cannot post files to, but you can post file contents to replies, and you can post files to web-sharing sites and then post a link to the file(s) on

Hope this helps! Please let us know how you progress with resolving the problems.
Disc cavity temperatures tell us about the status of turbine hot gas path components specially blades/vanes inner temperature. If DC temperature are high, then it means either cooling air is flow is less, or blades seals are not working properly and hot gases are going towards inner side of blades/vanes causing turbine output loss as well as decreasing parts life.