西三线0.8设计系数段环焊缝容许缺陷尺寸

为减少管材用量、降低工程造价,西三线27#阀室一烟墩压气站间300 km管道采用了0.8设计系数,相比以往的0.72设计系数,管道的安全设计系数由1.39降为1.25,管道环向应力水平相比提高11.5％.针对0.8设计系数的上述特点,在介绍目前国内外管道环焊缝焊接缺陷确定方法的基础上,重点对相关方法和检测标准进行对比和差异分析.基于西三线0.8设计系数段的实际工况,采用API 1104-2005标准中推荐的工程临界评估（ECA）方法,计算分析了管道环焊缝的容许缺陷尺寸,认为西二线无损检测规范规定的容许缺陷尺寸可以适用于西三线0.8设计系数段.

Tolerable flaw size of girth weld for the 3rd West-to-East Gas Pipeline with a design coefficient of 0.8

In order to reduce pipe consumption and engineering cost,a design coefficient of 0.8 is chosen for a 3 00 kmlong pipeline between 27# valve station to Yandun Compressor Station on the 3rd West-to-East Gas Pipeline.Compared with the previous design coefficient of 0.72,the pipeline safety coefficient is decreased from 1.39 to 1.25,and the pipeline hoop stress level is increased by 11.5 ％.Aiming at the above features of the 0.8 design coefficient,this paper highlights comparative and differential analysis on the relevant methods and testing standards based on brief introduction of global determination methods of pipeline girth weld defects.According to real working conditions of the pipeline with the design coefficient of 0.8,engineering critical assessment （ECA） method recommended in API 1104 standard is applied,the tolerable flaw size of the pipeline girth welds is computed and analyzed,and it is thought that the tolerable flaw size prescribed in the nondestructive testing standards of the 2nd West-to-East Gas Pipeline Project is also applicable to the 3rd West-to-East Gas Pipeline sections with the design coefficient of 0.8.（2 Tables,2 Figures,8 References）