Continuous Monitoring for Condenser Air In-leakage

Stroman, W.H., & Harpster, J.W.
“Continuous Monitoring for Condenser Air In-leakage” ASME Research Committee on Power Plant & Environmental Chemistry, Charleston, SC, March 11-13, 2002.

Abstract

Many of the new combined cycle units being installed utilize minimal manpower to operate the plant.  The rate of condenser air in-leakage is often dependent on the ability of plant personnel to recognize an abnormal increase in condenser back pressure with an occasional air removal exhaust discharge flow meter reading taken as time permits.  Frequently, plant staff are not aware of or are not concerned with subtle effects of elevated air in-leakage into the condenser steam side.

For all plants employing steam surface condensers, the effect of oxygen and carbon dioxide from air ingress can promote corrosion of system metallurgy.  Corrosion and corrosion byproducts can affect equipment life, unit reliability and availability.  Cation conductivity is also affected by the amount of carbon dioxide that is absorbed into the condensate.

Two-shift operation of units, particularly units that go offline overnight or through weekends, with air in-leakage, have the potential to affect performance and produce conditions for high dissolved oxygen and carbon dioxide.  Cycling puts more emphasis on the need for continuous monitoring of the exhaust rate of the air removal system.  Continuous monitoring provides operations with the ability to log the data output and to determine the baseline and deviations in relationship to the operation of the unit during startup, shutdown and during service.  A MultiSensor Probe (MSP) system is discussed for use in continuous condenser air in-leakage monitoring and measuring the operating conditions of the condenser and its air removal section.  The use of this instrument ensures that optimum performance is known and maintained.