Experimental Study And Data Analysis Of Valve Leakage Detection Based On Acoustic Emission Technology

Valves are widely used in important fields such as petroleum,chemical industry and nuclear power in order to control the flow and shut-off of fluid medium in pipelines.Their sealing performance is an important performance index.Valve leakage will cause energy waste,environmental pollution,and even threaten the safety of workers.Therefore,it is of great significance and wide application prospect to carry out the on-line fault diagnosis and leakage quantitative detection of valve.In order to study the relationship between the leakage signal and the leakage rate,the valve leak detection experiment platform based on the acoustic emission sensor was set up in the valve assembly inspection workshop of Chongqing Chuanyi Automation Co.,Ltd.Three types of valves,HTS,HCP and HSN,were tested in the leak detection experiments under the condition of three kinds of pressures,0.35 MPa,0.5MPa and 0.8MPa and four kinds of valve diameters,32 mm,40mm,80 mm and 100 mm.A large amount of experimental data was collected through the experiments.The patterns of valve leakage signal characteristic and leakage rate are studied according to the experimental data.The amplitude spectrum of the leak signal and non-leak signal are calculated and compared to determine the frequency range of the valve leakage acoustic emission signal which is 31 kHz ~ 33 kHz.A large number of analysis and comparison show that the valve diameter,valve type and pressure will not change the frequency band of the valve leakage acoustic emission signal.Therefore,a Butterworth bandpass filter with a pass band of 31 kHz to 33 kHz is designed to filter the valve leakage acoustic emission signal.The filtered signal is analyzed in the time domain and the frequency domain.Each set of data is segmented,and the amplitude squared sum in the time domain and the power spectral area in the frequency domain are calculated to extract two features of the leakage signal,i.e.the time domain energy and frequency domain area.The least squares method is used to fit the time domain energy and leakage rate,and the frequency domain area and leakage rate,respectively.The fitting results show that both the time domain energy and the leakage rate,and the frequency domain area and the leakage rate are in a linear relationship y(28)a(9)x(10)b,and their fitting degrees are close to 1.It is proved that there is a linear relationship between the leakage signal features and the leakage rate.