Hi everybody

We have GE 9E 125 MW simple cycle gas turbines. I try to write turbine cleaning system operation instruction. Does anyone use this system? I can not find valve line-up and operation steps in GE manual. I just have a P&ID 0441 PID TURBINE CLEANING.

 

HI Redstar,

Do you mean pulse cleaning system?

take care
g.rajesh

 

g.rajesh,

I believe he's referring to abrasive cleaning, who's must be done while running at rated speed using ground walnut shells as the cleaning medium. It impacts the compressor blades to try to dislodge stubborn contaminants from the blading. The ground walnuts shells do not damage the blading and do eventually get pulverized as they bass through the compressor before being burnt in the combustors. They very small particles do not expand when burning and don't cause the flame detectors to be obstructed-/unless they are dumped too fast from the hopper on the inlet plenum above the compressor bellmouth.

About the only precaution to take is to temporarily close any manual isolation valve upstream of a bearing cooling and sealing air dirt separator, and then throttling the separator blowdown valve opening as the inlet isolation valve is opened and then ensure the inlet valve is left fully open and the blowdown valve fully closed. (Not all units are equipped with bearing cooling and sealing air dirt separators; depends on the environment the unit was installed in. And, if a unit does have a separator the inlet valve should be fully closed and the blowdown valve fully open during off-line water washing.) Unfortunately, most such separators are under the axial compressor inside the turbine compartment--and most sites will not allow personnel to enter the turbine compartment when the unit is running. However, if it's decided to send someone into the turbine compartment to operate the valves while the turbine is running (NOT recommended!) the whole operation should not take more than 10 minutes start to finish to restore cooling and sealing air to the bearings as quickly as possible.

Hope this helps!

By the way, abrasive cleaning is really only effective on certain types of contaminants and compressor inlet humidity is high, allowing the contaminants to adhere to the axial compressor blading. Abrasive cleaning is not used very much at all, and again it's really only effective on some contaminants--not all. The amount to use is usually recommended by the abrasive cleaning supplier. And the rate at which it is introduced should not be very fast but not very long, either; a hopper full of medium should take be admitted over a period of 5-7 minutes.