Hull Assembly Research Articles

An Approach to Shrinkage Recovery of Hull Assembly by Computer-Aided Design System

Shrinkage value in a hull part increases by every heating of welding and straitening at the production process of sub-assembly, assembly, etc.This recovery used to be solved by adding its net dimentions many types of excess.This report describes an approach to the solution by introduction of the computer-aided hull parts generation system which has been already applied.The logic is to configure and fabricate the hull parts digitized in the system in their gross size including the shrinkage value, and the features are to operate the system as follows ;1) Design department prepares the net data output of the hull part configuration, and porduction department department provides their gross data output.2) Excess length for the shrinkage recovery is given at not only both the ends but also all the heating internals of the hull parts.

NEMO Type Acrylic Plastic Spherical Hull for Manned Operation to 3000 ft Depth

NEMO Mod 2000 acrylic plastic pressure hull assembly represents the latest addition to the NEMO hull series represented by NEMO Mod 600 and 1000 hull assemblies. The 66 in. OD × 58 in. ID spherical acrylic hull with aluminum hatches has successfully withstood 24 hr long external hydrostatic pressurizations to 450, 900, 1350, and 1800 psi. Pressure cycling and short term destructive testing of 15 in. OD × 13 in. ID scale models has shown that the crackfree fatigue life is in excess of 1000 pressure cycles to 1500 psi and the short term implosion pressure is in the range of 4750–5000 psi. Stress wave emissions have been found to be a good indicator of incipient failure. NEMO Mod 2000 spherical pressure hulls with panoramic visibility are considered to be acceptable for manned submersibles with 3000 ft operational depth capability. The cyclic fatigue life of such hulls is conservatively predicted to be at least 12 × 106 ft hr.

A Proposal on Modernization of Assembly Line of Curved Panel Units of Ship's Hull (1 st Report)

This report deals with the specific methods for modernization of the assembly line of the curved panel units.One of the vital problems in the modern shipbuilding industry is the modernization by means of mechanization and automation, to overcome insufficient labor sources in the recent years, during the hull assembly process. Conventionally, the modernization of the hull assembly process has been achieved mainly by the automation of the welding, but it has been limited to be applicable to the flat panel units only. However, the hull, as its movements are much related to the stream-line, the adoption of the stream-line is indispensable, and the fore and the aft parts of the hull naturally include the curved panel units. These curved panel units usually are made up with three dimensional faces, furthermore, each unit has different shape and arrangement. For this reason, it has been considered impossible to apply the mechanization and the automation, and the assembly work has had to rely on the skilled workers, therefore, at present it requires more skilled workers than in the case of work on the flat panel units. Also, in consideration of adoption of the flow line production system for the assembly process, the work is often interrupted by the dangerous turn-over of the units for the safety's sake, which causes considerable occasions of waiting time, one of obstacles in the flow line production sytsem for the assembly process.From the viewpoints mentioned above, the authors have conducted checkings for the modrenization in extensive fields of the assembly processes of curved panel units, and as its first stage, we developed the automatic assembly apparatuses for the curved panel, composed of the forming jack device, the welding positioner, and the one-side automatic welding machine.

Plate Sliding Type Automatic One Side Welding in Assembly Stage of Hull Construction

Intending to apply an assembly-line-production, a mass production medium, to the assembly of flat blocks, it is essential for the plate joining work which is the beginning of the whole production to be applicable to the assembly-line-production.The conventional plates joining method is such that the right side of the plates is initially welded and the reverse side is also welded after turning them over. But the busy crane program in many cases prevents a smooth progress of work since the crane is not provided exclusively for this process. So, if such welding method, capable of welding two plates together in one process from the right side to the extreme reverse side, is available, it can eliminate such extra works as turnover and welding reverse side and can creates a smoother flow of material. Of various methods of automatic one side welding, the one we have developed is “Plate sliding type automatic one side welding” that the steel plates to be welded slide themselves through the welding point of a fixed welding machine, under neath which there is a piece of copper plate to keep pushing up the reverse side of the plates being welded.By this process, the plates are welded together from the extreme right side to the extreme reverse side.This particular welding method has required us so much study in the process of development especially regarding welding method itself and the holding copper plate system because of the fact that it is different in many respects from ordinary welding methods which hold steel plates to be welded still. As a result of our thorough study, we have successfully developed an automatic one side welding method capable of welding to the extreme reverse side of the plate in one process capable of handling plates, 10 mm to 40 mm in thickness and 10 m to 20 m in length. This new method is now being applied to our hull assembly work in factory.