Can an ECA mitigate the requirement of performing PWHT?

Post Weld Heat Treatment (PWHT) is applied to relax the residual stresses within the weld 和 reduce the risk of brittle fracture by improving 断裂韧性. However, with improved modern welding techniques is PWHT still necessary? 

The use of PWHT is a common requirement when using thick-walled components as part of the ASME boiler codes. PWHT is required for pipes exceeding 1 ¼” thickness or approximately 32mm.

The case study below investigates the requirement for PWHT, it looks at how im体育APP’s energy team performed Engineering Critical Assessment (ECA) to avoid PWHT 和 investigates the client benefits to using this methodology. 

所面临的挑战

我们的客户, in the 气体 transmission / 能源 industry, approached us to investigate if using Post Weld Heat Treatment (PWHT) for one of their pipes with a 46mm wall thickness was required. 

This pipe had already been coated, 对内对外, 和 the application of PWHT would badly damage these coatings. Consequently, if PWHT was avoided, these coatings could be preserved.

除了, PWHT on such a large pipe was logistically difficult 和 time-consuming, 和 the client was working on a very tight schedule.

解决方案 

为了应对这一挑战, im体育APP’s technical experts advised the client on the necessary input requirements to gain a full underst和ing of the component in service, 和 also guided the client on the testing required to perform the ECA. 

im体育APP performed an ECA to establish if the maximum workmanship flaw, e.g. the largest permissible flaw in the structure, was acceptable in the absence of PWHT. The team investigated if PWHT added an overall benefit 和 concluded that even in the absence of PWHT the workmanship flaw was acceptable. The assessment showed that the PWHT was not providing any benefit to the integrity of the component. To verify this, im体育APP performed project-specific 断裂韧性 和 拉伸试验, where the testing was conducted on non-PWHT material. 

Using the testing data combined with the design data specific to this component, the maximum workmanship flaws were assessed as per the guidance of BS 7910, which assesses the significance of flaws, using fracture mechanics approaches.

结果

Using ECA 和 im体育APP’s integrated testing 和 analysis solutions helped avoid damage to the previously applied coatings 和 removed an unnecessary process that would take time 和 add significant cost to the project. As a result, the client could meet their schedule 和 save both time 和 money on their project.

The client was confident in the integrity of im体育APP’s approach as industry-recognized codes 和 st和ards were followed to prove that their component was fully acceptable in the absence of PWHT.

The client has now performed additional testing, which demonstrates the actual material properties, such as 断裂韧性 和 tensile properties, instead of relying on generic code compliance. The testing required for the ECA is more thorough testing than the testing required without the PWHT waiver 和 will increase the integrity of the component, 减少维修费用, 和 can be used to extend the life of the component. 

To learn more about Post Weld Heat Treatment (PWHT) 和 Engineering Critical Assessment (ECA), 或者如果你有任何问题, 今天就im体育APP的团队.