Residual stress distribution in girth weld of oil and gas pipeline

Key words:  residual stress of girth weld  coercivity method  ultrasonic method  blind hole method  numerical computation

Abstract:

The residual stress of the girth weld of natural gas pipeline directly affects the bearing capacity and safety margin of the pipeline. The numerical computation on the thermal cycling process on the welding of two steel plates was carried out, in order to determine the distribution characteristics of residual stress in the weld and surrounding areas. Then an experimental study was conducted on a large-diameter and long-distance natural gas pipeline with girth welds. The coercivity method, ultrasonic method and blind hole method were used to characterize the girth welds and the surrounding residual stress of the pipeline, and then the distribution characteristics of residual stress were studied. The results show that the residual stress distribution characteristics of weld and heat affected zone of the two methods are roughly consistent. The study shows that the coercive force method can accurately describe the distribution characteristics of residual stress in the girth weld and surrounding areas of the pipeline. This study can provide an important online nondestructive measurement and evaluation method for ensuring the service safety of welded pipelines.