On our Frame 9 Gas Turbine running at base load, one of the compressor beeld valves opened due to its control air tube breaking apart. We closed the manual isolation valve of the bleed valve. Is it safe to run the turbine in this condition? What are the possible dangers? It is difficult to be able to work in the turbine compartment to replace the broken tube due to hot temperature and pressure. Any comments would be helpful.

 

Not safe at all. If the unit trips while the manual isolation valve is closed and no one is close by to open that valve quickly, there may be compressor stall during coastdown. Also, if some were standing by during a shutdown and for some reason couldn't get the valve open during shutdown, there could be a compressor stall. Make sure there are proper "tools", such a pipe of larger enough diameter to slip over the end of the manual isolation valve's handle to use as a "cheater" to help open the valve if it sticks.

The one good thing here is that there is another bleed valve which should open during a trip/shutdown and that might provide enough of a flow to help protect the unit. Usually though, the output of the Compressor Bleed Valve Solenoid which ports air pressure to the two actuators for the two valve is "split" into two lines so it would seem that if the tubing for the air to the actuator for one valve split that it would allow the pressure to bleed out of the other actuator. Are you running with both manual bleed valves closed??? This could be a real problem if the unit were to trip and no one were available to open the valves quickly or couldn't get them both open quickly.

In any case it's recommended you shut the unit down and repair the tubing as quickly as possible--with someone standing by to open the manual isolation valve(s) as soon as the load gets within 1-2 MW just before the breaker opens, then let the breaker open and let the unit coast down.

markvguy

 

Other than the excessive noise generated, problem with operating the turbine with the bleed valve open is that you won't be able to load the machine. Once of the requirements for completing the startup sequence is that both bleed valves must be closed, once the turbine reaches 14HS speed.

A note of caution:

Keep a close watch on the bearing and wheel space temperatures.

And the final word on this should come from GE.

 

The originator said that the manual isolation valve of the compressor bleed valve which had opened had been closed and was not asking if the turbine could be operated with one or more compressor bleed valves opened--only if it was safe to operate with the manual isolation valve closed.

You are however, correct, that if a GE-design heavy-duty gas turbine were to be operated under loaded conditions with a compressor bleed valve open that close attention should be paid to wheelspace- and bearing temperatures as it will adversely affect the Cooling and Sealing Air flows to those areas.

Under such a condition, you are also correct--GE should be consulted and have the last word.

And, finally, you are also correct--that rated load could not be achieved if operating with an open compressor bleed valve.

markvguy

 

Thanks for your reply. While we were thinking to make a decision to shut down the turbine, the GT unloaded and shutdown due to burning of exhaust frame cooling air blower motor. Then we replaced the motor as well as air tube for the compressor bleed valve and started the turbine without a problem.

 

Thanks for the feedback! Sorry to hear about the blower motor, but sometimes things work out for the best.

Many times there are ways to get around a seemingly small failure or glitch, but sometimes the risk is greater than the reward. If one ever experiences a compressor stall, he/she won't want to be around another one! The amount of damage can be as surprising as it is expensive.

markvguy

 

What will happen if compressor Bleed valve gets open during gas turbine running at base load?

 

Read the above listed.
E-design heavy-duty gas turbine were to be operated under loaded conditions with a compressor bleed valve open that close attention should be paid to wheelspace- and bearing temperatures as it will adversely affect the Cooling and Sealing Air flows to those areas.

Under such a condition, you are also correct--GE should be consulted and have the last word.

And, finally, you are also correct--that rated load could not be achieved if operating with an open compressor bleed valve.