Comparison of two theoretical models for electric leak location at landfill

To solve the disability of conventional model used in electrical leak location when measurement electrodes were buried under the liner, a new model of high voltage DC leak detection is developed. For single-liner landfill, the waste material layer, the geomembrane liner and the soil under the liner are simulated with infinite horizontal layers. The leak is regarded as two parts, one being negative current source at the entrance, and the other positive current source of the same size at the exit. Comparisons between the new theoretical model and conventional model show that conventional model is efficient in locating leaks in geomembane liner associating the dipole scanning above the liner but is ineffective when the measurement electrodes were buried under the liner. The new theoretical model data are in excellent agreement with experimental data not only above the liner but also under the liner.

Research on Leak Location Method of Water Supply Pipeline Based on MVMD

At present,the leakage rate of the water distribution network in China is still high,and the waste of water resources caused by water distribution network leakage is quite serious every year.Therefore,the location of pipeline leakage is of great significance for saving water resources and reducing economic losses.Acoustic emission technology is the most widely used pipeline leak location technology.The traditional non-stationary random signal de-noising method mainly relies on the estimation of noise parameters,ignoring periodic noise and components unrelated to pipeline leakage.Aiming at the above problems,this paper proposes a leak location method for water supply pipelines based on a multivariate variational mode decomposition algorithm.This method combines the two parameters of the energy loss coefficient and the correlation coefficient between adjacent modes,and adaptively determines the decomposition mode number K according to the characteristics of the signal itself.According to the correlation coefficient,the effective component is selected to reconstruct the signal and the cross-correlation time delay is estimated to determine the location of the pipeline leakage point.The experimental results show that this method has higher accuracy than the cross-correlation method based on VMD and the cross-correlation method based on EMD,and the average relative positioning error is less than 2.2%.

Research on Leak Location of Liquid-filled Pipe Based on Frequency Dispersion Characteristics

Due to the material problems and force majeure factors,the leakage will be occurred on the liquid-filled pipe resulting in waste of resources,environmental pollution and even endangering safety.Acoustic wave detection technology is widely used in buried pipeline leak detection,this technology mainly uses the wave(n=0,s=1)in the pipeline acoustic wave to locate the leak.When the leakage acoustic signal propagates along the liquid-filled pipe,the frequency dispersion characteristics can be obtained by wavelet decomposition.And there is a time delay(time difference)value between the leaky acoustic signals collected by the sensors at both ends of the leak.The outputs show that the results obtained by wavelet decomposition are in good agreement with the theoretical calculation results.Based on the obtained dispersion relation,the time delay values at different characteristic frequencies are analyzed by the cross-correlation method,and the leak location accuracy is discussed.This research content provides theoretical support and engineering application guidance for pipe leakage location technology.

A Fast Leak Locating Method Based on Wavelet Transform

The problem of leak location is actually a time delay estimation（TDE） problem.Since most existing TDE methods may encounter the problem of high computational complexity when used for online leak location.This paper presents a fast leak locating method based on wavelet transform（WT）.The method first gets a rough estimate of the time delay from the WT coefficients of the pressure signals at the largest scale,then keeps refining the estimate using WT coefficients on smaller and smaller scales.Quantitative analyses and test results based on real data show that the method reduces the computational complexity while maintaining the time delay estimation accuracy.

Real-Time Pressure Based Diagnosis Method for Oil Pipeline Leakage

As detecting the pressure signal is the main method in the real-time leak diagnosis of long pipeline, an abnormal pressure diagnosis method is proposed to make the leak diagnosis rapidly and accurately. Firstly, a combination filter algorithm is designed to realize noise reduction. Then, an anomaly detection algorithm is designed to detect abnormal pressure on the head and tail of the pipeline. Finally, the relevancy of the detected novelties is computed by Pearson correlation coefficient to identify the leakages. The experimental results show that the proposed method can rapidly detect the leakage with few false alarms and accurately locate the position of the leakage. © 2017, Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg.