A 9 foot diameter, 60 foot long Stripper Vessel was designed and fabricated to be placed in service at a refinery in the Virgin Islands. Prior to starting service, the client wished to cover the top 20 feet of the shell inner surface with Inconel 625 weld overlay to protect the shell base metal against corrosion. O’Donnell accepted the challenge to design a weld overlay process, proper welding sequence, and apply the overlay while controlling the distortion of vessel. The weld overlay of the vessel required preliminary weld qualifications in accordance with the ASME Code Section IX, Welding and Brazing Qualifications. This dictates the welding of test plates, non-destructive and destructive testing of the test plates, and documentation of all the welding variables and test data. The welding equipment used in the test cases and in the actual overlay was a very sophisticated Pulse Spray Gas Metal Arc system which is capable of of capturing a specific welding electronic wave form, storing it in unique welding schedules.
Temperature measurements were taken on the back side of the test plates for use in a FEA distortion analysis. The measurements were also used for the design of a water cooling system. Bead overlap, weld travel speeds, interpass temperature, and other essential welding variables were adjusted and documented during the test welding, and subsequently incorporated into the final Welding Procedure Specification.