The present work investigates the influence of welding sequence and scheme on residual stresses
induced during in-service sleeve repair welding of gas pipelines. For this purpose, a 3D thermomechanical
FE analysis is conducted on an 800-Schedule-20, API 5L-X65 steel pipe. Two welding sequences
for the sleeve-pipe circumferential fillet welds are compared in the present study: sequential
welding in which one side of the sleeve is welded first and then the other side is welded by the same
welder, and simultaneous welding in which both sides of the sleeve are welded concurrently by two
welders. Within the simultaneous welding sequence, four different welding schemes, designed to
investigate the influence of the number of welders and welding directions on residual stresses, are
investigated. The results show that the sequential welding sequence induces less residual stresses and
distortions. Within the simultaneous welding sequence, the back-step welding scheme is found to induce
the least average residual stresses as compared to other welding schemes.