Dear sir,

We have two 6B Gas turbine duel fuel machine. Both Machine Running part load with ECS control, ECS contol with Grid Setpoint of 1 MW Unity P.F. SO ECS system has to control Grid setpoint while varying the both GT Load as they are selected in Auto Mode.

Few Days Back Around Five times GT#2 load got fluctuation while other GT running normal, Load fluctuation was not there from the Plant or from grid , it was GT load malfunctioning so, We have s/d GT and Clean bypass fuel control valve filter by air, Now after we have started 5 times it is getting trip on excess fuel flow trip & Exhaust Temp. High Trip. What would be the solution on this machine to start safely.

 

Let's take this a step at a time.

1) Load fluctuations means fuel flow fluctuations for one reason or another. Looks like your Liquid fuel control was unstable. Was FSR fluctuating?

2) Cleaning of fuel bypass filter with air?? Can you explain your procedure a little more please?

3) Try to re-start and you are getting Excessive Fuel Flow and/or Exhuast Temp Trips (Yikes!!). To be honest, it looks like the Bypass valve is totally stuck.

4)Solution to start safely. I wouldn't try again, even one more time until you try to resolve this liquid fuel control problem.Trips on "Excessive Flow" are reasonably OK, High Exhaust Temp. trips are not OK. It looks like you had an unstable bypass valve and in removing and trying to clean, you have made it even worse. What spares do you have ? Can you replace servo and/or Bypass valve. If you can then try a "dummy" fire first (Fire with no spark plugs) and monitor fuel flow for stability and correct flow for "Fire" FSR.

Please fill in some more information for us. All the normal stuff. Any recent maintenance activities, any previous fuel control issues, any data, trip logs.,etc.

What is ECS? and how a 1 MW Grid set-point on a Frame 6??

 

I would go along with Bob's fears. In fact I would advise not to start again without somehow having a visual inspection of the back-end of the turbine - blades etc. There could be damage there causing the issue. Can you get into exhaust (safely following procedures) and note the condition.

Only then would I start looking at control issues.

 

Hi,

Well said by Mr. Bob

Fuel by pass valve (VC3) is full open and caused excessive fuel and over temperature trip.

As Johnston said try one false start fire and observe all parameters.

If VC3 not closing then change the servo valve and try.

Check for the startup permissive and look for any other alarms.

Are you running your unit is ISO mode?

Take care
G.Rajesh