X80天然气管道在役焊接应力分析与调控

为了探究X80天然气管道在役焊接的应力分布和变化规律，在考虑天然气介质的作用下，采用有限元方法模拟了X80天然气管道在役焊接应力场分布规律，分析了天然气工况参数和环境温度对X80天然气管道在役焊接应力的影响，并根据应力变化规律提出了降低X80天然气管道在役焊接应力的措施。研究结果表明:X80天然气管道轴向焊接应力和环向应力主要呈对称分布形式，且管道外壁的应力大于管道内壁上的应力；随着天然气压力和流速逐渐增大，轴向应力先增加后降低，而环向应力逐渐增大；当环境温度增大后，管道轴向和环向应力均呈下降趋势；降低天然气压力和流速、采用焊前预热能够有效降低焊接应力。研究结果可为我国X80天然气管道在役焊接安全提供参考。

Analysis and control of in service welding stress for X80 natural gas pipeline

In order to explore the distribution and change laws of in service welding stress on X80 natural gas pipeline, the distribution laws of in service welding stress field on X80 natural gas pipeline were simulated by using the finite element method with considering the effect of natural gas medium. The influence of operating parameters of natural gas and environmental temperature on the in service welding stress of X80 natural gas pipeline was analyzed, and the measures to reduce the in service welding stress of X80 natural gas pipeline were put forward according to the change laws of stress. The results showed that the axial welding stress and hoop stress of X80 natural gas pipeline mainly presented the form of symmetrical distribution, and the stress on the outer wall of the pipeline was greater than that on the inner wall. Along with the gradually increasing pressure and flow velocity of natural gas, the axial stress increased first and then decreased, while the hoop stress increased gradually. When the environmental temperature increased, both the axial and hoop stress of the pipeline decreased. Therefore, the welding stress could be effectively reduced by reducing the pressure and flow velocity of natural gas and adopting the preheating before welding. The results can provide the reference for the safety of in service welding on X80 natural gas pipelines in China.