Otahuhu B Power Station condenser in-leakage analysis and condensate monitoring system : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Electronics Engineering at Massey University, Wellington, New Zealand
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Date
2008
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Massey University
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Abstract
Considerable ongoing risk of condenser in-leakage exists at Otahuhu B (OTB) Power
Station. The condenser cooling water used at OTB station is corrosive brackish water
with exceedingly high sodium and chloride concentrations. Significant signs of
corrosion inside the condenser have been found recently. In the event of condenser
in-leakage, the salt contaminants in the cooling water will directly enter the Heat
Recovery Steam Generator (HRSG) with the potential for significant and costly damage
resulting in a long plant outage.
A dynamic mathematical model was developed in the thesis to analyse the
consequences of condenser in-leakage at OTB station. The analysis results show that the
tolerance of the condenser to any leakage of cooling water is almost zero. Because the
existing condensate monitoring system is not designed to detect contamination in this
time frame, a new fast response system is required to detect condenser in-leakage
immediately.
A new dedicated fast response condensate monitoring system has been engineered and
installed at OTB station as a part of the project scope. The new system dramatically
reduces the response time to condenser in-leakage events. Critical instruments utilise
multiple redundancy schemes to enhance the availability and reliability of the system. In
addition, action level voting, timing, and alarming has been automated to assist
operators in making correct decisions.
The new condensate monitoring system is presently fully functional. The project has
successfully achieved the objective of controlling the risk of condenser in-leakage
events and minimising damage and negative effects on the plant.
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Keywords
Corrosion, Condensate monitoring system, Cooling water