Research On Pipeline Leak Detection And Location Based On Negative Pressure Wave Method

Pipeline transportation has unique advantages in transporting natural gas and water etc.However,leakage happens inevitably due to man-made damages or pipeline defects.Because the pipeline is usually installed in the underground and stretches for thousands of miles,people cannot through direct contact and pipeline detection and location of leakage.The paper,based on the negative pressure wave method,determines whether the pipeline leak and further locate the leak location by monitoring the pressure of the pipeline at the end of the trend.It is found that many factors affect the accuracy of leak location,especially the negative pressure wave velocity and the elbow.Therefore,in this paper,an auxiliary pressure sensor is added to the original negative pressure wave leak detection and location system and the influence of the curvature radius of the elbow is studied on the leakage location.This paper mainly studied influences of void fraction & temperature on sound velocity and proposed schemes about calibrating wave velocity in the experiment.The noise reduction effect of mean filtering,median filtering and wavelet filtering were compared.The advantages and disadvantages of the wavelet transform method,cross-correlation method and maximum slope method for extracting pressure signal singularity were analyzed.The experiment analyzed influences of size and position of leakage hole,inlet pressure and sampling period on pipeline leak detection and positioning.Numerical simulation was adopted to simulate flow field near pipeline leakage holes and then analyzed velocity field,pressure field and turbulent flow field.The experiment analyzed leakage signals under inlet pressure of different pipelines as well as different leak hole size.The pressure variation trend which the fluid flow through the elbow was researched.The attenuation law of negative pressure waves near pipeline elbow with different curvature radiuses and influences of different elbow curvature radiuses were analyzed on accuracy of pipeline leak positioning.The results show that the noise reduction effect of wavelet filtering is better than the mean filtering and median filtering.Using wavelet analysis method to capture the signal singularity is not only accurate but also can judge the properties of singularity compared with the cross-correlation method and the maximum slope method.The greater leakage hole is,the greater inlet pressure is,the smaller sampling period is,the farther leakage hole position is away from the pipe elbow,the higher the leakage detection sensitivity and positioning accuracy are.The leakage signal with the increase of inlet pressure and leak becomes stronger.When the radius of curvature of the elbow is 3 times or 4 times than the diameter of the pipe,the accuracy of the leakage positioning is better.