Sweepolet Pipe Intersection

This example shows analysis of defects at the header and branch weld locations of a sweepolet pipe intersection. The header pipe has a 36 inch outer diameter and the branch an 8 inch outer diameter. This pipework is used in gas transmission pipelines.

The analyses required the modelling of full circumferential defects of various depths at two weld locations - one in the header and one in the branch. Defects were to be considered on the inner and outer walls. Due to the load cases that were analysed it was necessary to generate a full model in addition to quarter and half symmetry models. The combination of load cases, crack sizes and crack positions gave a total requirement of more than 100 separate analyses.

The finite element model consisted of 20 noded brick elements in the pipe intersection region with 8 noded shells away from the intersection.

The analyses generated stress intensity factor distributions along the crack fronts. These were used as input to a reliability analysis.