长输管道斜对接环焊缝的安全评定

Safety assessment of oblique butt girth weld in long distance pipeline

在长输管道运行期间,经内检测发现缺陷后,采用适用性评价方法可在保障管道安全的前提下,避免大量经济损失。采用适用性评价方法对某工程钢管斜对接环焊缝缺陷进行了评价,同时基于有限元模拟,进一步明确了斜对接环焊缝在不同运行工况下的受力情况。计算结果表明,斜对接环焊缝剩余强度满足适用性评价要求,在目前实际运行压力下,环焊缝处应力均在标准规定的允许值范围内,斜接环焊缝可在监控下继续使用。管道安装闭合环境温度和运行压力的变化会直接影响斜接环焊缝处的应力水平,若管道运行压力变化时,斜接环焊缝是否能继续使用需要结合压力和温差等情况,合理确定。

In the operation stage of long distance pipeline project, defects that detected could be assessed by fitnessfor service method to ensure the safety of the pipeline and avoid a great deal of economic losses. Angular misalignment girth weld in one project was conducted by fitness-for service method, and meanwhile finite element simulation was carried out to further clarify the stress in different operating conditions. The calculation results showed that the residual strength of the angular misalignment girth weld met the requirements of fitness-for service evaluation, and the stresses for the actual operation pressure were in the standard allowable range. So the girth weld might be continue used under surveillance. The change of environment temperature for installation and operating pressure would directly affect the weld stress level. Once operation pressure was changed, whether the girth weld could be used should be reasonable determined by combination of pressure and temperature difference, etc..