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本文根据聚乙烯夹克耐环境应力开裂的基本理论,分析了华北油田提供的“埋地输油管线φ529mm 黄夹克开裂现状”的书面报告,提出了聚乙烯夹克的开裂不仅仅是工艺问题,环境和材料也是导致开裂的重要因素,因此,防止夹克开裂应从以下三个方面考虑:1.改进材质,主要途径是①采用分子量分布适应的低、中密度聚乙烯;②高、低密度聚乙烯共混;③选用共聚性聚乙烯。2.改善底胶,主要途径是以聚乙烯为主剂与其他助剂制成或者在底胶中加入“应力抑制剂”。3.改革工艺,途径是①表面处理除清除钢材表面附着物外,还应在钢材表面造成一定深度的锚纹;②应开展分段冷却工艺的研究,③施胶和包覆工艺要进行改进,可采用充臭氧施胶工艺和负压包覆。
Based on the basic theory of environmental stress cracking resistance of polyethylene jackets, this paper analyzes the written report of cracking status of φ529mm yellow jacket provided by Huabei Oilfield. It is proposed that the cracking of polyethylene jacket is not only a matter of process, but also the environment and materials Therefore, to prevent jacket cracking should be considered from the following three aspects: 1. To improve the material, the main approach is ① using low and medium density polyethylene adapted to molecular weight distribution; ② high and low density polyethylene blend; ③ selection of copolymerized polyethylene. 2. Improve the end of plastic, the main approach is to polyethylene-based and other additives made of the main agent or in the end of the glue by adding “stress inhibitors.” 3. The reform process, the way is ① surface treatment in addition to removing the steel surface attachments, the steel surface should also cause a certain depth of the anchor pattern; ② should be carried out sub-cooling process, ③ sizing and coating process to be improved , Can be filled with ozone sizing process and negative pressure coating.