We have 4 Frame 9E GE gas turbines with dual fuel. In two of our gas turbines there is frequent VCK-2 (liquid fuel line NRV) valve passing.
Whenever we change the valves they again starting passing. I have a question about the atomising air circuit, maybe the atomising air temp is less than the designed value.

Can anyone tell about the effect of low atomising air temp, or the probable cause of failure of this valve? What should the correct atomising air temp be for safe operation?

You can mail me at bsjhala at ntpc. co. in

 

I don't know if this really qualifies as a control problem or issue....

The temperature of the air entering the Atomizing Air Compressor is what's important. It should be high enough to prevent condensation but less than approximately 135 deg C (275 deg F) to prevent damage to the Atomizing Air Compressor which usually spins at very high RPM (some of them at approximately 44,000 RPM). I believe the Device Summary says the Atomizing Air Temperature Regulating Valve is to be set to control the Atomizing Air Pre-cooler Discharge Temperature to about 107 deg C (225 deg F). Again, the fear of low Atomizing Air Compressor inlet temperature is that condensation may form and enter the compressor.

It's odd that you say you have four machines but only experience the failures on two of the machines. Were all four machines installed at the same time?

Do all four machines use the same check valve?

Do the units burn diesel or naptha or some other liquid fuel or multiple liquid fuels?

Do the units burn natural gas?

How often do the units that experience the higher failure rates burn liquid fuel?

Do all units operate at the same loads when operating on liquid fuel?

Liquid Fuel and Purge check valves have historically been problematic for GE. They have new check valves and there have been other posts to control.com about other options.

I don't think AA temperature is what's causing the liquid fuel check valves to fail. The only time that atomizing air would be in contact with the liquid fuel check valves would be during purging when operating on gas fuel.

I've seen Frame 9E check valves pass (in the opposite direction) and the Liq Fuel Stop Valve (VS1) also open and allow air (hot combustion gases) to flow back into the liquid fuel system. This is not very good, and also usually results in air pockets in the top of the Liq. Fuel Filter canister, which can cause problems when trying to transfer to liquid fuel in an emergency situation.

Again, there are options for this non-control system related problem.

 

Replies to CSA...

1) Yes all four machines have same type of check valves.
2 and 3) We have Dual fuel option. Mostly machines on natural gas, sometimes on naptha fuel, HSD is used as transferring fuel only.

I have a observation that the units in which there is frequent VCK2 failure, Atomising Air temp is somewhat lower compared to other unit.

What can be the probable cause of frequent failure?