Research On Valve Inner Leakage Monitoring Of Liquid Pipeline With Acoustic Method

As a kind of fluid control equipment,valves are widely used in the important fields of national economic construction such as power station construction,petrochemical development and improvement of urban construction systems.However,in the process of valve application,due to aging,corrosion and improper operation,the valve leakage problem is serious.Therefore,it is of great significance to study valve leakage detection methods.For the detection of valve leakage faults,scholars at home and abroad have done a lot of research and proposed detection methods such as pressure drop method,thermal infrared method,vibration method,acoustic emission method and acoustic wave method.The vibration detection method has high detection sensitivity but poor anti-interference ability.The acoustic emission method has good stability,but the signal processing is complicated,and the high hardware cost is not conducive to the realization of the project.The acoustic wave method based on dual sensors whose frequency of acoustic signals is low is conducive to engineering implementation.However,at the present stage,researchers use a fixed threshold method for internal leakage signal diagnosis.The sensitivity and adaptability of operating conditions are greatly affected by the threshold.This paper presents a non-intrusive acoustic monitoring method for inner leakage of valves based on single sensor.A complete simulation experiment platform for internal leakage faults of valves was designed and built;a simulation device for transient internal leakage of valves through the combination of flanges,aluminum sheets with holes and thin paper sheets was proposed and designed;The design of software and hardware for the acoustic signal acquisition system is completed.A low-frequency(0?20Hz)acoustic signal generated by the fluid turbulence when the internal leakage fault occurs in the valve can be collected by an acoustic sensor installing on the wall of the valve downstream that can realize the monitoring of the valve internal leakage.According to the difference of the time-frequency features of the output signal of the acoustic wave sensor under normal condition and internal leakage condition of the valve,From the point of view of gaussianity of acoustic signal,a time-domain feature extraction method based on the kurtosis coefficient was proposed.From the point of view of energy distribution in the frequency domain of acoustic signals,a time-frequency domain feature extraction method for acoustic signals based on wavelet packet energy fractionation is proposed.The abnormal signal diagnosis model based on support vector data description method(SVDD)was established by using the time-frequency domain feature vector samples under valve closed normally.The experimental results show that the proposed method for valve internal leakage acoustic monitor can effectively identify the abnormal signal of inner leakage of the valve in different working conditions,and has strong anti-interference ability and high detection sensitivity.At the same time,the requirements for signal sampling frequency are low,which provides an effective and reliable technical means for valve leakage monitoring engineering applications.