Research On Blockage Detection Technology Of Natural Gas Pipeline

The consumption and use of natural gas in China is increasing day by day,and the mileage of natural gas pipeline is increasing day by day.Impurities such as water,condensate oil and hydrate contained in the transportation pipeline will gradually gather,accumulate and form blockage,which will endanger the safety of the pipeline.Therefore,it is of great significance to accurately and quickly detect the pipeline blockage position and realize the blockage early warning to ensure the safety of natural gas pipeline flow.Based on the research background of natural gas pipeline blockage detection,aiming at the existing limitations of pressure wave and acoustic wave blockage detection technology,theoretical and experimental studies are carried out respectively,and corresponding blockage detection schemes are put forward for different engineering scenarios.Among them,for complex gas pipelines,a set of pressure wave method blockage detection technology has been developed,and a complex structure pressure wave signal processing method combining frequency spectrum analysis and FFT harmonic transformation has been established.Based on FFT high-frequency low-pass filtering method,the accurate location of blockage with multiple blockage rates has been realized.Aiming at the long-distance gas pipeline,a set of acoustic wave blockage detection technology is developed,and the theory of blockage signal analysis and detection based on acoustic wave method is established.The experimental results provide experimental support for the engineering application of these two blockage detection technologies,and provide guidance for the selection of different pipeline blockage detection schemes.The specific conclusions are as follows:(1)According to the easy-to-block sections of engineering pipelines,such as branch pipes and blind pipes,a pressure pulse wave complex gas pipeline blockage detection system with multiple tee branches and blind ends is built,which verifies the effectiveness of pressure wave in detecting complex pipeline blockage.The designed acoustic gas pipeline blockage detection system can simulate the field working conditions of natural gas pipelines,and realize multitype and multi-material blockage detection under high-pressure pipelines.(2)A signal processing method of complex structure pressure wave is established,which combines spectrum analysis with FFT harmonic transformation,and based on FFT highfrequency low-pass filtering method,the accurate location of congestion with multiple congestion rates is realized.Experiments on blockage location of gas-liquid pipeline with different blockage rates are carried out.The results show that the three-way structure will cause high-frequency reflected waves with the frequency range of 150-200 Hz,and FFT harmonic transformation method is more conducive to the analysis of blockage location.Among them,when the blocking rate is 50%,the positioning error is the largest,which is 1.93%.For the gasliquid mixed pipeline with liquid content of 8%,the positioning error is 0.48% when it is 100%blocked.It shows that the positioning accuracy of pressure wave method in detecting complex pipeline blockage can meet the actual engineering requirements.(3)The theory of blockage signal analysis and detection based on acoustic wave method is established,and many kinds of blockage detection experiments of long-distance gas pipelines under high and low frequency nonlinear frequency modulation acoustic waves are carried out.The results show that the maximum average positioning error is 0.26% for extended blockage,and the detection accuracy of short blockage with high frequency sound wave is obviously better than that with low frequency sound wave.Using the low-frequency sound wave detection results to calculate the blockage area,the average error detection difference of four groups of experiments is 8.32%.For single-point blockage,accurate positioning can be achieved,but the blockage length and blockage area cannot be calculated.For ice jam,the reflection characteristics of sound wave are the same as that of segment jam,and the location and length of jam can be accurately predicted.However,due to the influence of the shape of the jam section,the calculation error of the cross-section jam rate is larger than that of segment jam.For water blockage,the acoustic reflection signal is slightly different from that of other substances,and the calculation error of cross-section blockage rate is too large,but the blockage position and length can still be calculated.It shows that acoustic wave method is an effective method to detect the blockage of long-distance pipelines.