Influence of squeeze-off on the mechanical properties of PE gas pipes
ZHANG Yi, XUE Shifeng, HAN Limei, LIU Cuiwei, JIAO Junpeng
(1. College of Pipeline and Civil Engineering, China University of Petroleum - East China, Qingdao, Shandong 266580, China; 2. Shandong Key Laboratory of Oil & Gas Storage and Transportation, Qingdao, Shandong 266580, China)
Abstract：Squeeze-off is a dedicated pipeline construction and rush repair technology which is designed on the basis of the good toughness of polythene (PE) pipes, and it has been extensively applied in recent years. However, non-standard squeeze-off can bring damage to PE pipes, shorten its service life and even severely impact the safe operation of gas pipes. In order to establish a safe and efficient squeeze-off process and ensure the safe operation of PE gas pipes, this paper investigates the influential laws of squeeze-off on the mechanical properties of PE pipes by means of laboratory experiments and finite element simulation. And the influences of extrusion speed, wall compressibility, size of extrusion rod and friction coefficient between pipe and extrusion rod on the maximum pipe stress and plastic strain are mainly analyzed. And the following research results were obtained. First, the elastic modulus and yield stress at the ear of PE pipes after the application of squeeze-off are only 17% and 72% of the original values. Second, maximum pipe load, stress and plastic strain increase with the increase of extrusion speed and wall compressibility. Third, as the size of the extrusion rod decreases, the maximum extrusion load decreases, but the maximum pipe stress and plastic strain increase significantly. Fourth, reducing the friction coefficient between pipe and extrusion rod is beneficial to the reduction of maximum pipe stress and plastic strain. In conclusion, the squeeze-off can deteriorate the mechanical properties of PE pipes, so it is suggested to apply some necessary protection measures to the squeezed off PE pipes and especially its ear. What's more, increasing the size of extrusion tool and reducing the friction coefficient between pipeline and extrusion rod can lead to the reduction of pipe stress and plastic strain, which is beneficial to the safe operation of PE pipe.
张毅，薛世峰，韩丽美，刘翠伟，焦俊朋. 压扁阻断对聚乙烯燃气管道力学性能的影响[J]. 天然气工业, 2020, 40(11): 135-142.
ZHANG Yi, XUE Shifeng, HAN Limei, LIU Cuiwei, JIAO Junpeng. Influence of squeeze-off on the mechanical properties of PE gas pipes. NATURAL GAS INDUSTRY, 2020, 40(11): 135-142.
