Leak location in gas pipelines using cross-time–frequency spectrum of leakage-induced acoustic vibrations

Natural gas is a vital energy carrier which can serve as an energy source, which is extremely vulnerable to leakages from pipeline transportation systems. The required ignition energy is low. Although the safety of natural gas pipelines has been improved, the average economic loss of natural gas accidents, including leaks, is large. To solve these problems, an acoustic leak localization system is designed and researched for gas pipelines using experiments with methods proposed according to different application situations. The traditional method with two sensors installed at both ends can be improved by a newly proposed combined signal-processing method, which is applied for the case that it is necessary to calculate the time differences with data synchronicity. When the time differences cannot be calculated accurately, a new method based on the amplitude attenuation model is proposed. Using these methods, the system can be applied to most situations. Next, an experimental facility at the laboratory scale is established, and experiments are carried out. Finally, the methods are verified and applied for leak localization. The results show that this research can provide a foundation for the proposed methods. The maximum experimental leak localization errors for the methods are −0.592%, and −7.62%. It is concluded that the system with the new methods can be applied to protect and monitor natural gas pipelines.

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Improved EEMD in the Application of Signal Singularity Detection

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.518-523.3847 ◽

2012 ◽

Vol 518-523 ◽

pp. 3847-3851

Author(s):

Mei Jun Zhang ◽

Chuang Wang ◽

Hao Chen ◽

Qun Zhang Tu

Keyword(s):

Frequency Spectrum ◽

Original Data ◽

Singularity Detection ◽

Time Frequency ◽

Local Characteristics ◽

Cross Terms ◽

Marginal Spectrum ◽

Frequency Components ◽

Detection Signal ◽

Improved Eemd

In order to solve the endpoint effect and modal aliasing phenomenon in EMD and EEMD,Improved EEMD is put forward, and the application in signal singularity detection is researched in this paper. The improved EEMD will signal drops down into a series of different IMF to highlight the different local characteristics of original data, and then calculate Hilbert marginal spectrum and time-frequency spectrum to determine the frequency of these mutations and mutations position. To compared with FT, STFT, WVD,WT, EMD and EEMD etc, No cross-terms and no false IMF components are produced in the Hilbert time-frequency spectrum of the improved EEMD. Different frequency components and frequency mutations position are clearly distinguished at the same time. The Hilbert time-frequency spectrum of the improved EEMD has more superior detection signal singularity ability.

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Non-Gaussian Wave Groups Generated in an Offshore Wave Basin

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4006394 ◽

2012 ◽

Vol 134 (4) ◽

Cited By ~ 6

Author(s):

Z. Cherneva ◽

C. Guedes Soares

Keyword(s):

Gaussian Process ◽

Frequency Spectrum ◽

Local Spectrum ◽

Wave Groups ◽

High Wave ◽

Time Frequency ◽

Wave Basin ◽

The Mean ◽

Non Gaussian ◽

Experimental Runs

The main goal of the present paper is to study the differences of the descriptors of the wave groups in the nonlinear case in comparison with the same parameters for a Gaussian process. The data analyzed are from a deep water basin of Marintek. They consist of sequence of five identical independent experimental runs of unidirectional waves measured at ten fixed points situated in different distances from the wave maker. Each series contain about 1800 waves. Thus the statistics collected from a given gauge comprise about 9000 waves combined in a number of wave groups. Because the series describe a process significantly different from the Gaussian one, an upper and lower envelopes are introduced as lines which connect the peaks of the crests and the lower points of the troughs respectively. Spline functions are applied to calculate these envelopes. Then, the mean high run and mean group length are estimated for different levels, their ensemble average over five experimental runs is found for every gauge and is compared with the results of the theory of Gaussian process. It is found that the values of the mean time intervals of the groups correlate with coefficient of kurtosis of the process. It is determined also that mean group length is shorter and the mean high run is larger for the nonlinear wave groups in comparison with the Gaussian wave groups. The modification of wave groups in space and time is investigated in the work as well. Wigner time-frequency spectrum with Choi-Williams kernel is applied to describe the process of entire modulation and demodulation of the groups. It is found that before formation of the high wave a wave down-shifting takes place. At this stage the local spectrum is relatively narrow and the group shrinks continuously. Close to the focus the time-frequency spectrum is very wide and the group has a triangle form. Further the high wave breaks and the wave group acquires the form of “three sisters.” The transform of the group continues by its disintegration, the local spectrum stands narrow and an up-shifting is observed.

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Joint time-frequency spectrum sensing for Cognitive Radio

2010 3rd International Symposium on Applied Sciences in Biomedical and Communication Technologies (ISABEL 2010) ◽

10.1109/isabel.2010.5702774 ◽

2010 ◽

Cited By ~ 3

Author(s):

Wael Guibene ◽

Aawatif Hayar

Keyword(s):

Cognitive Radio ◽

Frequency Spectrum ◽

Spectrum Sensing ◽

Time Frequency

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A new leak location method based on leakage acoustic waves for oil and gas pipelines

Journal of Loss Prevention in the Process Industries ◽

10.1016/j.jlp.2015.05.006 ◽

2015 ◽

Vol 35 ◽

pp. 236-246 ◽

Cited By ~ 46

Author(s):

Cui-wei Liu ◽

Yu-xing Li ◽

Yu-kun Yan ◽

Jun-tao Fu ◽

Yu-qian Zhang

Keyword(s):

Acoustic Waves ◽

Oil And Gas ◽

Gas Pipelines ◽

Location Method ◽

Leak Location ◽

Oil And Gas Pipelines

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Seismic time-frequency spectral decomposition by matching pursuit

Geophysics ◽

10.1190/1.2387109 ◽

2007 ◽

Vol 72 (1) ◽

pp. V13-V20 ◽

Cited By ~ 143

Author(s):

Yanghua Wang

Keyword(s):

Frequency Spectrum ◽

Acoustic Waves ◽

Large Scale ◽

Matching Pursuit ◽

Low Frequency ◽

Gas Reservoir ◽

Adaptive Wavelet ◽

Redundant Dictionary ◽

Time Frequency ◽

Wavelet Selection

A seismic trace may be decomposed into a series of wavelets that match their time-frequency signature by using a matching pursuit algorithm, an iterative procedure of wavelet selection among a large and redundant dictionary. For reflection seismic signals, the Morlet wavelet may be employed, because it can represent quantitatively the energy attenuation and velocity dispersion of acoustic waves propagating through porous media. The efficiency of an adaptive wavelet selection is improved by making first a preliminary estimate and then a localized refining search, whereas complex-trace attributes and derived analytical expressions are also used in various stages. For a constituent wavelet, the scale is an important adaptive parameter that controls the width of wavelet in time and the bandwidth of the frequency spectrum. After matching pursuit decomposition, deleting wavelets with either very small or very large scale values can suppress spikes and sinusoid functions effectively from the time-frequency spectrum. This time-frequency spectrum may be used in turn for lithological analysis—for instance, detection of a gas reservoir. Investigation shows that the low-frequency shadow associated with a carbonate gas reservoir still exists, even high-frequency amplitudes are compensated by inverse-[Formula: see text] filtering.

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