Development of grounding device to reduce current variationin submerged arc welding process for pressure vessel fabrication

This study developed a device to solve welding problems that occur in the manufacturing of a pressure vessel for cryogenic applications under the ASME Section VIII Division 1. The cylindrical body of the vessel was assembled with short pre-fabricated cylinders and caps using submerged arc welding. The rotatable grounding electrode was mounted to the top half of the spherical cap. However, the relatively long distance between the welding and the electrode grounding locations, especially in longer vessels, restricts the flow and the distribution of the electrical current. Radiographic testing identified lack of fusion as the major reason for the restricted flow of the electrical current. This also caused additional work on welding repair. To address this issue that compromised both top-outer and bottom-inner vertical positions for circumference welding, a new grounding device was developed to reduce the flow distance. The electrical conductivity was also improved through a series of welding tests. The investigation showed that a greater average welding current increased arc stability. Radiographic testing confirmed that the vessels were welded completely suggesting the grounding device utility for increasing welding joint soundness of the circumference weldment.