I used to work for an oil company in Alberta Canada. The new upgrader they built has 10 PSA vessels which they have no experience with. Because we didn't want to remove the catalyst, we exposed all weld seams by removing the insulation and conducted 100% TOFD inspection on all circ and long seams and manual shear wave on all nozzle welds, which included the skirt to shell weld. We also visually inspected for peaking at seam locations; particularly at the long seams. Hope this helps Scott