Sub-Assemblies

When plates and sections have been machined they are ready for assembly into ship units. Within the fabrications shop there are often arranged a number of bays for different assemblies, for example flat plate panels, curved shell units, matrix or ‘egg box’ structures and some minor sub-assemblies. All these may be termed sub-assemblies if they are subsequently to be built into a large unit prior to erection. Panel assembly is usually highly automated with prepared plates being placed and tack welded prior to automatic welding of the butts, after which the plates are turned and back welded unless a single sided weld process has been used. The panel is marked and the stiffeners placed and welded automatically or with semi-automatic process. Minor sub-assemblies such as deep frames consisting of web and welded face flat may also be attached at this stage. Curved shell plates are placed on jigs and welded and the various stiffening members can be aligned and welded in a similar manner to those on a flat panel assembly. Assembly jigs may also be used for matrix or ‘egg box’ assemblies, for example structures of solid and bracket plate floors with longitudinal side girders which are to go into double bottom units.