Sequential block welding

Sequential block welding sets the order in which hull blocks and their internal joints are welded so that shrinkage forces cancel rather than accumulate, controlling overall hull distortion during erection. Welding proceeds from a fixed reference outward, often symmetrically about the centerline and from the neutral axis, so each weld’s pull is balanced by an opposite weld. Erection joints close with controlled root gaps and back-step or skip passes to spread heat. The aim is to keep the keel fair and the blocks dimensionally true without late flame straightening. The sequence is planned alongside the welding distortion prediction and the assembly schedule.