There are two main types of building procedures. One is the frame erection system which was prevalent before 1950 and the other is the block assembling system adopted by almost all shipyards today. In this guidance, the building procedure employed is assumed to be the block assembling system.
Frame erecting system
This is an old practice adopted for wooden ships in many years ago and continuously adopted for iron and steel ships of riveted construction in the 19th Century. Even now, some small shipyards continue to use this method.
Block assembling system
During the World War II, the construction of new ships was needed as quickly as possible and this system was adopted in some shipyards using new welding techniques. Hull construction is divided into many parts depending on the crane capacity of the shipyard, (one part called a block, unit or sub-assembly) and each block is fabricated independently. The blocks are then positioned in the building berth and welded to each other starting with bottom then the side and finally the deck construction.
In the early days of the Block assembling system, outfitting work was carried out after completion of hull construction in the same way as the old practice but now this is carried out during block fabrication as called Pre-outfitting. For example, piping, valves and other equipment are installed in each block beforehand.
Procedural flow of survey work during construction
The items, frequency of inspection, and general flow of the classification survey during construction depends on the practice, capacity, productivity and quality control system of each shipyard.
Store room: Paints, consumables, stainless steel, equipment, machinery protection ect.,
Steel bay: Scales, marking, trace-ability ect.,
Block bay: Fairing, cutting, repairing, pre-outfitting ect.,
Dry Dock: Erection fit-up, alignment, dimension, leveling, safety access ect.,
To know how the Ship hull produced and what kind of essential works have to be carried out at each area/stage, Please find out in below attachment – Working flow chart for Hull item.
Conclusion: Understanding the ship structure work flow can help the shipyard optimize the time, thus reducing the building time and cost. In Surveyor’s point of view, understanding the work flow helping to organize and co-ordinate the work scopes properly and make the potential risks proactively mitigated.