Moisture Separation in Condenser Vent Lines

Harpster, T.J., Harpster, J.W., Fields, R., Stalling, J., & Tsou, J.

“Moisture Separation in Condenser Vent Lines” EPRI Condenser Technology Conference St. Petersburg, FL August 13-14, 2009


Suspended liquid phase water has been detected in the flowing noncondensable gas/water vapor mixtures found in condenser vent lines of some condensers. Identification of this inadvertent liquid was determined from evaluation of the output signal from RheoVac® vent line monitors, also known as MultiSensor Probes (MSPs). These instruments are designed for measurement of condenser air in-leakage, water vapor-to-air mass ratio of flowing mixture, and venting equipment working capacity. The accuracy of these important condenser performance related measurements is adversely affected by the presence of this entrained water. The identified intruder is also known to decrease venting equipment capacity for air removal and cause an increase in the demand for condensate makeup water, both having a cost impact on the unit.

To remove the deleterious effects of water on vent line flow measurements, without resorting to retrofitting the condenser to remove the root cause, two low cost removal methods were devised. Because of the importance of the MSP measurement to power plant condenser performance monitoring and diagnostics, EPRI sponsored testing of these methods to evaluate their effectiveness. Reporting the results of this test program and the reasons behind the successful result is the purpose of this paper and presentation.

A short summary of the project findings are:

  • The MSP measurements are 100% protected when both the in-line and separator tips (MSTs) are implemented over the entire 8-month test period.
  • The MSP measurements assisted in identifying and quantifying an out of calibration condenser pressure sensor.
  • The MSP measurements show adequate venting even when the unit has a 100 SCFM air in-leak for the entire 8-month time period.
  • The separated entrained water was measured up to ~1.5 gpm.

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