Acoustic emission detection and defect identification method for micro-leakage in natural gas pipeline valves
ZHANG Lizhen1,WANG Wen'ao2
1.Department of Safety Supervision and Management, Chongqing Vocational Institute of Safety Technology; 2.College of Mechanical and Electronic Engineering, China University of Petroleum (East China)
[Objective] The pivotal role valves play in ensuring the stable operation of natural gas pipeline systems necessitates real-time monitoring and defect identification to eliminate early leakage in natural gas valves. To this end, it is imperative to develop an effective method for detecting and identifying micro-leakage defects. [Methods] An acoustic emission detection experimental setup was initially established targeting valve micro-leakage, with three pressure settings of 0.2 MPa, 0.4 MPa, and 0.6 MPa. This self-developed setup was utilized to capture the acoustic emission signals across five valve conditions (healthy state, external leakage due to valve stem corrosion, internal leakage due to untightness in valve closure, internal leakage due to valve core scratch, and external leakage due to flange gasket damage) through the acoustic emission detection method. The collected signals were then used to create time-frequency domain feature matrices. These intricate and redundant time-frequency domain feature matrices were transformed into two-dimensional and three-dimensional feature factor matrices utilizing Principal Component Analysis (PCA). The optimal number of clusters for each feature factor matrix was determined through subsequent calculations. The two-dimensional and three-dimensional feature factor matrices were further analyzed using K-means and K-medoids clustering methods. [Results] For the identification of micro-leakage defects of natural gas valves under low pressure conditions (0.2 MPa), the clustering effect of 3D PCA reached 97.8%, surpassing that of 2D PCA. As the pressure was gradually raised to 0.6 MPa, the clustering effect of 2D PCA continued to improve, eventually surpassing that of 3D PCA. In the evaluation of clustering methods, it was observed that the K-medoids method exhibited greater stability and higher operational efficiency compared to the K-means method. [Conclusion] The classified processing method for acoustic emission signals, based on acoustic emission technology, feature extraction, PCA, and clustering algorithms, can enhance the accuracy and stability of valve micro-leakage detection. Moreover, it enables the classified identification of defects in natural gas pipeline valves. This approach not only offers monitoring means but also establishes safeguard measures crucial for ensuring the secure operation of natural gas pipeline systems. (7 Figures, 2 Tables, 26 References)
图4 不同压力下天然气管道阀门5种状态的PCA降维结果对比图Fig. 4 Pressure-varying comparison of PCA dimensionality reduction results of natural gas pipeline valves across five conditions
图6 压力为0.2 MPa下天然气管道阀门状态K-means与K-medoids聚类效果对比图Fig. 6 Comparison of K-means and K-medoids clustering effects across natural gas pipeline valve conditions at 0.2 MPa
图7 压力0.6 MPa下天然气管道阀门状态K-means与K-medoids聚类效果对比图Fig. 7 Comparison of K-means and K-medoids clustering effects across natural gas pipeline valve conditions at 0.6 MPa
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