Condenser Vacuum Transmitter Deviation Cook Nuclear Plant – Unit 1 Main Feed Pump Turbine Condensers – East and West

Background Information The Unit 1 East and West Main Feed Pump Turbines each have dedicated condensers separate from the main turbine condenser. The sensing pipes are ½” copper that are assembled by brazed connections. The sensing lines will accumulate or flood with condensate based upon the diameter of the sensing pipe.

We had three transmitters connected to the steam condenser. Two transmitters were connected to one sensing pipe and one transmitter was connected to another sensing pipe. Question: Why would we experience a deviation in vacuum between the pressure measured by two transmitters on one sensing pipe compared to the third transmitter on another sensing pipe in the summer and not in the winter?

Answer: The single transmitter connected to a sensing pipe was routed along side the MFP turbine. In the summer the water leg would boil off due to the warmer ambient conditions in the plant. The loss of this water leg would change the vacuum indication causing a deviation between the indications of the other two transmitters.

Typical Steam Condenser Vacuum Connection Capped for filling and calibration Transmitter

EPRI titled, “Condenser Performance Monitoring Practices “ Sensing line needs to be large enough to allow the condensation to drain back to the condenser - 1 inch steel pipe or tubing is adequate. Use eccentric reduce elbow or coupling if the connection at the condenser is ¾”.