Frame 6B Trips on Exhaust Overtemperature During Start Up at 33% TNH


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Our Frame 6 GT# tripped on exhaust overtemperature during cold start at 33% TNH

This GT# firing starts at 20% TNH. I queried the operator whether he heard anything abnormal or vibration after firing & also whether the false start drain valve was working correctly, he confirmed that all were OK.

After reaching standstill, we carried out a check inside the turbine compartment & found nothing abnormal. We re-started the GT# and found everything OK, exhaust spread was as usual (around 10Deg C at 5MW) and (23 Deg C) at full load. The flow of fuel to each combustion liner was OK with same figures, as usual.

Existing control system is Mark V TMR.

Please advise


would you check the turbine inlet air filter pressure (DP transmiter). because if the filter house is full of dirt, the compressor inlet wont have enough air to operate the turbine with and as a consequence of that the exhaust temperature would rise over the trip value at startup.

hope that helps
Sounds like this is a Liquid Fuel machine, is it? It's possible that you had some problems with air in the liquid fuel system on the first start which cleared, and your second start was OK, but, still unusual to get an Exhaust Temp. Trip. Did anyone check the Trip History Log to see what happened? Was any work done on the fuel system prior to starting?

The unit is liquid fuel fired. No works had been carried out on the unit or fuel system recently. However the unit is running rarely those days. Between 1 and 5 starts per month. I am suspecting that this was caused due to sticking of the moog 65fp servo-valve. This is mainly due to lub oil varnishing.

From the last Lub oil test carried in April 2016, Lub oil varnish (VPR level) is a little high, but not an extent that the oil requires replacement.