Research On Identification And Location Of Valve Leakage Based On Acoustic Analysis

Valve is an important part of the pipeline,extensively applied in industry,nuclear power,aviation and aerospace fields.However,Valve leakage often occurs because of the design,installation,usage and other aspects of problem.In the industrial production,valve leakage will not only lead to loss of media,but also may lead to the spread of toxic and hazardous substances and thus lead to fire and explosion accidents.Nuclear power plant valve leakage will seriously affect the safety and reliability of the operation of the power plant and even pose a threat to the safety of people’s lives.Aiming at the problem of valve leakage,this paper studies the method of identifying and locating the leakage of valve by using the technique of sound pressure measurement.The main work as follows:The main form and mechanism of the valve leakage and the basic theory of acoustics in the measurement of sound pressure are studied.On the basis of the above analysis,the feature extraction method of the acoustic pressure signal of the valve leakage is studied,including time domain waveform analysis,spectrum analysis,main change spectrum analysis,negative make zero spectrum analysis and spectrum energy analysis.Based on the time domain,frequency domain and spectrum energy,the feature extraction method of valve leakage sound pressure signal is studied.Based on the research of feature extraction method of valve leakage sound pressure signal,comprehensive use Lab VIEW and MATLAB software platform,corresponding analysis program is developed,and the algorithm of the main change spectrum analysis,the negative make zero spectrum analysis and the spectrum energy analysis are studied.An experimental platform was designed to simulate the leakage of the pipeline valve,and the possible leakage of pipeline valve is simulated under different experimental conditions.A sound pressure detection system is built which is made up of PCB microphone,NI9234 dynamic signal acquisition module,NI cDAQ-9174 4 slot USB chassis,Lab VIEW sound pressure acquisition program.The sound pressure measurement system can provide the data base for the analysis of the characteristics of the valve leakage pressure signal.Use valve leak identification and locating program,the measured data in pipeline valve leakage platform are analyzed.This paper discussed the advantages of the main change spectrum and n negative make zero spectrum in reducing the background noise and highlighting the characteristics of the leakage signal.Using the spectrum energy analysis,the frequency band is divided into three bands of high,medium and low.The signal characteristics of the leakage sound pressure signal in the spectral energy can be effectively revealed by the three-dimensional spectral energy plot.The accuracy of the cross-correlation time delay estimation method for the analysis of experimental data is analyzed at different cut-off frequencies.The location of the leakage valve is realized by the cross-correlation analysis of the sound pressure signal.