Hello,

I would like to ask about the role of the Bypass PCV and the reason for including Drum LEVEL HHH as one of the trip conditions for the Bypass PCV.

1. Role of Bypass PCV: The Bypass PCV (Pressure Control Valve) regulates steam quality during startup, preheats the steam line, and circulates steam to the condenser. It also acts as a safety valve by controlling system pressure during normal operations.
2. Reason for Including Drum LEVEL HHH in Trip Conditions: When the drum level reaches HHH (High-High-High), there is a significant risk of water carryover into the steam turbine. If the Bypass PCV remains open, the pressure in the drum decreases, potentially causing the drum level to rise further, increasing the risk of water ingress into the steam turbine. Therefore, to maintain drum pressure and stabilize the water level, the Bypass PCV needs to trip.

Is this understanding correct, and can anyone provide additional insights or explanations?

Thank you.

 

Yes, this is correct. If you are having trouble controlling drum level during a startup, the drum level control valve is probably leaking by.
If you are approaching HHH during startup and think you can ride through since the turbine is spinning up, you can pinch back on the Bypass to lower drum level even though it will raise your pressure a bit.