Research On Condition Monitoring And Fault Diagnosis Of Heat Exchangers For Power Plant

Fouling and leakage are two major serious faults in heat exchanger of steam turbine units. Seeking a monitoring method to solve the condition monitoring and fault diagnosis, especially a method which has no relations with the operating condition or not greatly dependence on operating condition, has important theory meaning and practical value of project in security and economical operating in heat exchanger of steam turbine units. This thesis has set up thermal efficiency analyzing model through using the heat transfer method used in designing and analyzing of heat exchanger, on the basis of thermal efficiency analyzing model, put forward a fault-diagnosis method for faults of fouling, leakage etc in heat exchanger, further more, a modifying method of eliminating the influence on monitoring result of operating condition is given. According to the heat transfer mechanism of the high-pressure heater, the whole heat transfer area is divided into superheated steam cooling section, steam condense section and dredge water cooling section , on the basis of thermal efficiency models of three sections, a diagnosis method for leakage fault is proposed, it is made easy to orient leaking position through subsection monitoring and be able to evaluate the degree of leakage through monitoring the"leaking percentage". On the foundation of separating the air accumulating of the vapor side from the fouling of the water side, it is advised a fault diagnosis method for fouling on the cooling water side based on the condensing efficiency model for condenser. Proved by simulation operating data, the dirty factor (Fouling%) is a characteristic variable which has no relations with vacuum tightness, circulating water flow and steam load, so, it can reflect the dirty degree of the water side truly. According to thermal efficiency mathematics model suitable for no phase state changing liquid, a diagnosis method for fouling fault in no phase state changing heat exchanger is proposed.With the operating data in faulty condition of domestic 200MW unit of power generation corporation, Ltd. in Xuzhou, using the diagnosis method for closing circulation cooler, high-pressure heater and condenser, the result has proved the validity and dependability of the monitoring and diagnosis method being above-mentioned.