Hello,
At combine cycle power plant we have 2 GE gas turbine 6FA and 1 steam turbine Doosan Skoda MTD 40 CA. Steam turbine have knocking sound from gear wheels when turning gear operating. We stopped turning gear and opened inspection cower and check gear well, found normal. Also turning gear unit started without synchronization and also found good. Sound appearing after turning gear synchronization when turbine shaft speed get 25rpm and more. Can someone give some recommendations with your experience?
P.S jacking oil pressure at all bearings is normal and also lube oil pressure is good.

Thank you.

 

Hello,
Did you find the root cause?

 

Hello,
Did you find the root cause?

Hello,
We invited Doosan Skoda engineers. They checked shaft teeth and can't find anything. After checking we started turning gear and noise was same. Later Skoda give us recommendation if noise will increase totally disassemble turning gear and check all bearings conditions.

 

How "young" is this steam turbine?

When was the last maintenance outage when the bearings might have been opened/disassembled/reassembled?

What type of bearings do the steam turbine and generator use?

Does this turbine have a load- or reduction gear between it and the generator it drives?

I have seen some turbines (steam and gas) that have very different inertias for the turbine and generator. Sometimes when bearings are "disturbed" during maintenance (including replacement with new or refurbished journal bearings) the tolerances have changed and this contributes to a little banging that is at least partially due to the necessary backlash in the gears of the turning gear mechanism. I have also seen some steam turbines what experience similar problems when vacuum is brought up as the unit is being readied for operation, particularly when there is a load- or reduction gear between the turbine and the generator.

But, that's all I got. It would be interesting if you could supply the requested information.