The Development Of Condition Monitoring And Fault Diagnosis System Of Control Valve

The pneumatic control valve installed in the industrial field, contacting with productionmedia directly, often works under high temperature, high pressure, high corrosion, erosion,vibration and other harsh environments. In order to precisely regulate the flow of the medium,the valve need frequent movements, so that it is prone to a variety of anomalies and failures.Once the control valve fails, it will lead to a lot of problems, such as increased energyconsumptions, lower-quality product, even safety issues or life-safety incidents. Therefore, itis necessary to develop the control valve diagnostic system. However, it is still blank in ourcountry.Firstly, the performance requirements of control valve are proposed. The main propertiesof control valve are divided into three types, namely flow regulating performance, valveposition control performance and load performance. And define performance indicators toexpress the corresponding performance.Secondly, a control valve performance diagnostic system is designed and developed,base on USB-6009data acquisition card produced by NI company. The hardware part of thediagnostic system is mainly composed of bridge power supply circuit, I/V conversion circuit,DC/DC boost circuit, V/I conversion circuit and other signal detection sensor. The detectionincludes the strain of valve stem, the pressure of gas source, the pressure of air chamber andvalve position. The software is designed and developed based on LabVIEW platform, it canbe divided into five functional blocks, which are parameter settings, sampling settings,channel selection, waveform display and generation of test reports, to facilitate expansion ofthe new valve types and to meet their functional requirements.Then, experiments are designed to test and evaluate the performances of control valve.Specific experimental control signal is applied under the given operating conditions, to detectthe signal of each variable of control valve, and to analyse and process the experimentalcurves, so that the performance parameters of the three categories can be obtainedQuantitative and qualitative assessment of the control valve performance is realized, byparameter calculation and analysis and by comparison between performance requirements oftheoretical design and relevant standards.Finally, fault examples of control valve with inner leakage are truly simulated by theflow experimental devices of laboratory to research the diagnose problems of the mostcommon failures. The failure is analysed and diagnosed precisely with gray correlation method, by flow regulating performance evaluation.This paper is completed base on extensive literatures and theoretical guidance, especiallythe development in the laboratory and the experimental study in the production workshop,which take nearly1000hours. Research results have been successfully applied in theproduction enterprises of nuclear power valve.