Design And Implementation Of Valve Leak Detection Portable Device Based On Acoustic Emission

Valve absolutely is necessary fluid control equipment.it is applied to the industry far and wide.It mainly realizes the flow and shut-off of the fluid medium in the pipeline,the sealing performance is one of the important indexes judging valve performance.Because of corrosion,aging or wrong operation,the long-used valve will have leakage,it is easy to cause safety accidents.Due to the large number of valves in the industry,the complex detection site may not be able to provide power equipment,and It is easy to find the external volve leakage,but finding the internal volve leakage is a difficult thing,and the vast majority of accidents are caused by the internal volve leakage.therefore,the study of effective detection of internal valve leakage of portable devices have important meaning.The research on valve leakage detection mainly includes the following research contents:The principle of detecting valve leakage by acoustic emission detection is studied,and a portable device for detecting valve leakage by acoustic emission technology is designed and implemented.The device is primarily consisted of portable power supply,low noise preamplifier,microcontroller,display module,data conveying module and memory module,which can amplify,collect,display,transmit and store signals and solve the problem of valve leakage detection.A low noise preamplifier is designed for the elastic wave signal produced when the valve leaks because of its weak and easy to be interfered.Three high-precision operational amplifiers are used to build a multi-stage amplifier circuit,and a filter corresponding to the frequency characteristic of leakage signal is designed,and a electromagnetic shielding box is designed to settle the trouble of low noise amplification of weak acoustic emission signals.Portable power supply is required for the device,the portable battery is used to provide voltage,and the boost circuit is designed.Due to the output noise of the battery itself and the noise introduced by the boost circuit,it is necessary to design a power filter to filter and denoise the output voltage signal to get a clean power signal,which resolves the trouble of portable device.Aiming at the data acquisition,analysis,display,transmission and storage of the valve leakage detection device,microcontroller is used to complete the embedded software programming,drive the built-in acquisition function and data transmission interface of the main controller,and solve the problems of data acquisition,analysis,display,transmission and storage of portable devices,and completes the field leak detection function.Lastly,the function of the designed equipment is tested,and the valve leakage detection platform is built,and the acoustic emission signal of the cut-off valve are collected under unequal leak rates.By comparing the frequency realm data when there is no leakage and the frequency realm data when there is leakage,the leakage feature frequency realm is determined.Through the threshold setting of the characteristic frequency band,the leakage of the valve is judged,and the on-site leakage detection is completed.Then the relationship between the leakage signal and the leakage rate is analyzed.The results show that there is a linear relationship between the feature frequency realm of the leakage signal and the leakage rate,which can be used to evaluate the leakage of field valves.