Category D weld joints are used in which seam areas?

• A. Longitudinal seam areas
• B. Circumferential seams around the vessel
• C. Butt joints at flange connections
• D. Fillet welded corners

Answer: (A)

Category D weld joints are used for the longitudinal seam areas of a cylindrical shell. The longitudinal seam runs along the length of the vessel, which gives it a distinct orientation and inspection considerations compared with other weld locations. This is why Category D is associated with those long, lengthwise seams. Circumferential seams, flange-area butt joints, and fillet-welded corners have different geometric and inspection implications and are not designated as the longitudinal seam category.