Control fluid pump of governing system-Pressure not developing

[Sandeep kumar]

Sir/Madam,
Due to motor problem, control fluid pump changed over from 1 to 2, but pump-2 was not able to develop pressure due to which 600 MW Turbo generator unit tripped.Later on pump-2 stopped and restarted again pressure started building and later on unit was synchronized.Can any one explain what might me the reason for pump not developing pressure during change over and same pump was developing pressure after restarting again???
Accumulator pressures in oil line are checked and they are fine..please suggest actions to be taken...

 

[ashtree]

Statistically it would be most likely to be a loss of prime event, but without more information it is impossible to say. Perhaps some running , stopping and starting , changes in levels etc allowed the pump to eventually prime and allowed a restart.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Rputvin]

You're asking us what in your process can impact pump pressure.

What kind of pump is this?

Was it running off the end of the curve from someone leaving a valve open? Was the discharge valve left shut and it was deadheading but not making pressure at the sensor location? Did any process conditions change? Are there any changes operators can make that will impact pump performance, such as valve settings, bypass or service loops, multiple flow paths, etc. Are there motorized valves or mechanical items in the loop that can impact pump performance, like mixing valves, modulating valves, pressure reducing/sustaining/regulating valves?

What was the amp draw during the time it wouldn't build pressure? Did it make any sounds, vibration, etc? Was it serviced between being stopped and restarted? "later on unit was synchronized"- what does this mean?

What is it pumping, and at what temperature? Was the fluid near the vapor pressure and potentially flashing at the pump suction?

What feeds the pumps? What are the suction conditions? Can they change? How do they change?

What is the target pressure needed? How is it measured? Was it producing ANY pressure, or just not enough to satisfy the pressure sensor? If it was producing some pressure how does that compare to the desired pressure, and where on the curve does that sit?

I suggest the immediate action is to learn more about your process, identify anything that will impact pump performance, collect data about the conditions during the event that may shed light on the cause of the issue, and work out what changed. And if you can't find anything open the pump up and see if there is something off internally.

 

[JJPellin]

You provided too little information. But I can make some educated guesses. If the main control oil pump is motor driven, the spare is probably driven by a steam turbine. The turbine driver may not have been running full speed. Perhaps a governor problem or inadequate steam conditions.

The control oil pumps are likely screw pumps. Each one is protected by a relief valve. The relief valve may have been stuck open. The manual bypass around the relief valve could have been left open.

Johnny Pellin

 

[JJPellin]

On rereading the original post, it is not clear if this was a manual pump switch or a trip of the main pump and auto-start of the spare pump. I am guessing auto-start. The accumulator pressures were normal, But did you fully test the accumulator for bladder integrity? I am guessing ruptured accumulator bladder.

Johnny Pellin