Introduction to the Shipbuilding Process
Large shipyards typically cover several hundred acres extended over two miles or more of waterfront property. These shipyards are in close proximity to deep water rivers, harbors, or protected bays, many of which have been further improved by seawalls, breakwaters, and dredged channels.
Shipyards in the United States are generally supplied with raw materials through access to rail lines, whereas those in Japan and Korea are principally supplied by waterborne vessels. European yards are supplied by both methods. Shipyard production facilities are set up to ease the flow of materials from point of disembarkation (usually rail head or pier) through various processing and fabrication shops in which steel plate, piping, and other components undergo surface treatment, cutting, bending, welding, and assembly. In most of the world's major shipyards, these operations are controlled by sophisticated computer-aided design/computer-aided manufacturing (CAD/CAM), computer-controlled inventory, and work-in-process systems, which are linked directly (e.g., commands to numerically-controlled machine tools) or indirectly (e.g., shop diagrams and work schedules) to the applicable production process area.
Large oceangoing vessels are commonly constructed by a process in which individual steel plates are first either bent (if they are to become an element of the ship's hull) or cut (to provide access ways for internal plumbing, electrical, or structural components). Following these operations, structural stiffeners and related components are welded to the plates to form a structural element of the vessel. These elements, in turn, are welded together into larger subassemblies until they reach a critical maximum size (usually dictated by the lifting capacity of the cranes and transport systems of each individual yard). The weight of each subassembly can be as much as 900 tons. These subassemblies are then outfitted with the assorted plumbing, electrical wiring, pumps, motors, lighting fixtures, and other apparatus that are to be in place in each particular area of the completed vessel.
The subassemblies are called "modules" or "blocks"; thus, the term "modular construction" is often applied to this production process. This system is considered more efficient than the original method of constructing vessels, in which the hull of the ship was first constructed on an inclined platform, and the internal outfitting of the vessel was subsequently completely from the bottom up, then end to end (in the case of plumbing and electrical wiring).
In genera1, U.S. shipyards tend to lag behind their foreign competitors with regard to investments in new, technologically advanced machinery, claiming that they do not have the necessary funds to invest in such equipment. This situation is also due, to some extent, to the difference in flexibility required in the construction of Naval vessels and commercial ships. Because of their complexity and uniqueness, Naval vessels require a more flexible approach to construction than do commercial ships. Commercial ships may be constructed using more automated processes, because these processes may be used in the construction of similar ships. The machinery used in U.S. yards tends to be older and less automated than that used in foreign yards. However, certain U.S. shipyards are planning to make new investments in capital equipment, including a new, technologically advanced drydock and automatic cutting, sandblasting, and painting machines. Certain yards are also planning to upgrade their crane-lifting capacities.
Few U.S. yards employ robotics in commercial ship production, whereas Asian shipyards use robotics extensively in their production process, particularly in their welding operations.39 European yards also employ robotics to a significant degree, especially in the cutting of steel profiles. Some robotics systems are more advanced than others (i.e., able to examine steel and discriminate between usable and unusable steel plates), but most are self-correcting, technologically advanced production tools.
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