Nowadays, polyethylene composes a large number of natural gas distribution pipelines installed under the ground. The focus of the present contribution is two fold. One of the objectives is to investigate the applicability of polyethylene fittings in joining polyethylene gas pipes which are electrofused onto the pipe ends and buried under the ground, by estimating stress distribution using finite element method. The second objective is to study the effectiveness of polyethylene repair patches which are used to mend the defected pipelines by performing a finite element analysis to calculate peak stress values. Buried polyethylene pipelines in the natural gas industry, can be imposed by sever loadings including the soil-structure interaction, traffic load, soil’s column weight, internal pressure, and thermal loads resulting from daily and/or seasonal temperature changes. Additionally, due to the application of pipe joints, and repair patches local stresses superimposed on the aforementioned loading effects. The pipe is assumed to be made of PE80 resin and its jointing socket, and the repair patch is PE100 material. The computational analysis of stresses and the computer simulations are performed using ANSYS commercial software. According to the results, the peak stress values take place in the middle of the fitting and at its internal surface. The maximum stress values in fitting and pipe are below the allowable stresses which shows the proper use of introduced fitting is applicable even in hot climate areas of Ahvaz, Iran. Although the buried pipe is imposed to the maximum values of stresses, the PE100 socket is more sensitive to a temperature drop. Furthermore, all four studied patch arrangements show significant reinforcing effects on the defected section of the buried PE gas pipe to transfer applied loads. Meanwhile, the defected buried medium density polyethylene gas pipe and its saddle fused patch can resist the imposed mechanical and thermal loads of 22°C temperature increase. Moreover, increasing the saddle fusion patch length to 12 inches reduces the maximum stress values in the pipe, significantly.

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研究埋入式聚乙烯燃气管道的贴片和修补片中的峰值应力

如今，聚乙烯构成了地下安装的大量天然气分配管道。目前的贡献有两个方面。目的之一是通过使用有限元方法估算应力分布，研究聚乙烯配件在连接聚乙烯燃气管道中的适用性，这些聚乙烯燃气管道电熔接到管道末端并埋在地下。第二个目标是通过执行有限元分析以计算峰值应力值，研究用于修补有缺陷的管道的聚乙烯修补剂的有效性。天然气行业中埋入地下的聚乙烯管道可能受到严重负荷的影响，包括土壤与结构的相互作用，交通负荷，土壤柱重，内部压力，以及每日和/或季节性温度变化导致的热负荷。另外，由于应用了管接头和修补件，局部应力会叠加在上述加载效果上。假定该管道由PE80树脂及其连接承窝制成，维修修补件为PE100材料。应力的计算分析和计算机仿真是使用ANSYS商业软件进行的。根据结果​​，应力峰值出现在配件的中部及其内表面。管件和管道中的最大应力值低于允许的应力，这表明正确使用引入的管件也适用于即使在伊朗阿瓦兹炎热的气候地区。尽管将埋管施加到最大应力值，PE100插座对温度下降更敏感。此外，所有四个研究的贴片布置都显示出对埋入PE燃气管道的缺陷部分的显着增强作用，以转移施加的载荷。同时，有缺陷的埋入式中密度聚乙烯燃气管道及其鞍形熔接片可抵抗22°C温度升高带来的机械和热负荷。此外，将鞍形熔接补丁长度增加到12英寸会显着降低管道中的最大应力值。有缺陷的埋入式中密度聚乙烯燃气管道及其鞍形熔接片可抵抗22°C温度升高带来的机械和热负荷。此外，将鞍形熔接补丁长度增加到12英寸会显着降低管道中的最大应力值。有缺陷的埋入式中密度聚乙烯燃气管道及其鞍形熔接片可抵抗22°C温度升高带来的机械和热负荷。此外，将鞍形熔接补丁长度增加到12英寸会显着降低管道中的最大应力值。