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Application of Valve Diagnosis Technology in Nuclear Power Plant Equipment Procurement
The AP1000 nuclear power unit is the third-generation PWR nuclear power unit designed by Westinghouse Electric Company and is currently being constructed in two locations, namely, Sanmen in Zhejiang and Haiyang in Shandong. AP1000 nuclear power valve number and type of many, including nuclear island there are more than 4,000. Valve function is normal, relates to the safety and economic operation of nuclear power plants, so the hidden valve fault can be diagnosed in advance, it is very important. Valve diagnosis test is to establish the parameter information of the valve by testing the valve actuator current / power (electric actuator) or air pressure (actuator), the torque and thrust of the valve stem and the valve operating time when the valve is delivered from the factory. During the later operation of the valve, the user through the on-line testing, compared with the factory diagnostic test parameters, found the valve recessive defects, the valve parts for repair and replacement. The traditional method of valve inspection is that when the unit is shut down or the equipment is under regular maintenance, the valve is disassembled and inspected. This method not only wastes time but also has high maintenance cost. Therefore, the AP1000 nuclear valve is very strict in procurement, and the active valve must be delivered from the factory Do a diagnostic test. 1 valve diagnosis system * Nuclear power valve diagnosis system equipment suppliers are mainly Teledyne, CraneNuclear and Fisher and other companies. Teledyne valve diagnostic system, for example, mainly by the portable signal processor and stress sensors and other components. 1.1 Portable Signal Processor The portable signal processor has 16 ports that can simultaneously capture 16 data types including valve opening / closing time, stem thrust and torque, electric actuator current, voltage and power. The diagnostic system based on Windows operating platform analysis diagnostic software TTSQuiklookII, provides a simple man-machine interface. In the measurement can be based on different measurement needs, use different sensors to collect information, the TTSQuiklookII analysis and processing, the final diagnosis of electric valve data and curves. The Teledyne device has a sampling frequency of 1000 counts per second so that when the measured current or voltage frequency is 50 Hz, there are 20 sample points giving a change in current or voltage over an alternating period of 0.02 s. A more adequate sampling point is conducive to each cycle of the current or voltage parameter changes in the analysis and comparison. In addition, the valve opening and closing process, thrust and torque and other changes in the information is within 0.01 ~ 0.10s change, only the sampling frequency is high enough to get a more accurate curve. 1.2 stress sensor stress sensor in the factory diagnosis test, the pressure sensor attached to the stem, the test done can be saved and continue to use. The inner surface of the stress sensor is arranged with a circuit. When the stem is deformed by force, the resistance of the Wheatstone bridge in the strain gauge changes, causing the current and voltage of the bridge to change. The data of current and voltage changes are converted into electrical signals Change, the formation of stem thrust and torque with the input signal relationship, after conversion can be thrust and torque (Figure 1). Figure 1 The working principle of the stress sensor 2 electric wedge gate valve factory diagnostic test 2.1 valve diagnostic test The diagnostic test AP1000 nuclear valve a total of eight units, is a domestic factory production DN100, the nominal pressure of 15MPa wedge gate valve test In the use of TeledyneQuiklookII electric valve diagnostic system. In the diagnostic test before each valve 10 Kai Kai, closed-action test to ensure that the valve Kai, closed freely. Then each valve carries out 4 no-load and load on / off test respectively. The test parameters include stem thrust, stem torque, valve opening / closing time, electric actuator current, resistance and power. For stem thrust and stem torque, the value of valve flap release from the valve seat, maximum operating value, average operating value, and value of the control switch tripped at valve opening / closing were taken separately.