Development of Grounding Device to Reduce Current Variation in Submerged Arc Welding Process for Pressure Vessel Fabrication

Abstract

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.

A Processing Approach Incorporating Copper Backing-Wheel Device in Submerged Arc Welding for Manufacturing Cryogenic Storage Tanks

“…The approach can be implemented using cost-effective reusable assisting and simple modifications to the cross-section preparation of the steel plate prior to the welding process. Furthermore, the new approach may be applied to other similar cylindrical vessel fabrication by incorporating the cross-section preparations methods used in this study as well as the other assisting device to facilitate the SAW process [2].…”

“…During the conventional assembly of cylindrical body [1], short pre-formed cylindrical sections fabricated by mechanical deformation and welding processes are jointed along their circumferences on a rotational welding fixture as shown in Fig. 1 [2]. A pair of welding edges is pre-formed in a V-shape groove [3].…”

Analysis of Plane Displacement of Pressure Vessels with Defects

“…Surface defects are usually visible and easy to observe and detect, while internal defects are hidden and dangerous, and the detection process is relatively difficult. At present, the commonly used nondestructive testing methods for internal defects include ultrasonic testing [1][2][3][4][5] , eddy current testing [6][7][8][9] , and radiographic testing [10,11] . The introduction is subject to the inspection principle, site environment, and other objective conditions.…”