Original Date: 02/10/2003
Revision Date: 01/18/2007
Best Practice : Form Versus Weld
Bender Shipbuilding and Repair Company, Inc. has introduced new and innovative construction processes for building ship bulkheads using v-crimping techniques in flat panels to provide strength, thus eliminating the need for welding stiffeners.
Previously, Bender Shipbuilding and Repair Company, Inc. fabricated non-structural bulkheads and pilothouses by welding. Flat non-structural bulkheads were fabricated by welding three-inch vertical steel stiffeners on 24-inch centers. Time needed to weld a single three-inch wide vertical stiffener to the ¼-inch flat plate was approximately 45 minutes. Pilothouses were fabricated by welding a sequence of three flat plates together. Special jigs were required to hold the plates in the proper position.
Bender representatives visited the Caterpillar facility located in Peoria, Illinois, to observe operation of a typical Computer Numerical Control (CNC) press brake. Bender and Caterpillar worked together to develop processes and parameters to v-crimp steel for bulkheads. Shortly afterward, in the fourth quarter of 1999, the new Pullmax 1100- ton press brake was placed into service. A special die was developed to fabricate new v-crimped non-structural bulkheads, entirely eliminating the need for welding the stiffeners. The American Bureau of Shipping gave Bender approval to use this process, which became the standard for fabricating all non-structural bulkheads. Only at special customer requests are welded bulkheads provided. Not only are these v-crimped bulkheads less expensive to fabricate, they add less overall weight. The time needed to form one vertical v-crimp is less than a minute.
Pilot house bulkheads are formed with two horizontal bends, replacing several hundred feet of welding with forming, and resulting in a stronger, more accurate bulkhead. Bender also won a contract to form the four-foot by two-foot ventilation fan blades used by Barron Fans on the Boston Big Dig tunnel construction project.
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