Temper bead technique application onto in-service welding pipelines

The greatest limitation of pipelines in-service welding is the risk of hydrogen assisted cracking due largely to the action of the accelerated cooling rate imposed to the weld. The foremost objective of this work was to study the effect of the temper bead technique applied to in service welding. The Higuchi methodology was then selected to determine de energy relations for the weld bead deposition sequence. Three types of welding had been made. The first one, in order to become possible the application of the study of Higuchi, consisted of several welding beads deposited onto existing pipes, with tap water flowing through the pipe during the welding. The second category of welding deposition was the conventional split sleeve welding like those used for pipeline repair. In the third stage of this work, a set of crossed welding deposition was used with 50% overlapping. All the welding beads were evaluated by chemical analysis, metallography and hardness. The temper bead technique has shown promising results. Complementary studies still have to be carried out in order to achieve the best welding performance.