Original Date: 07/21/2003
Revision Date: 01/18/2007
Best Practice : Modular Design, Construction and End Loading
Electric Boat Corporation, Quonset Point Facility implemented modular design and construction to enable the end- loading of submarines. End-loading construction processes develop hulls with better circular geometry and stability than those built by traditional bottom-up methods.
Electric Boat Corporation, Quonset Point Facility (EBQP) implemented modular construction to enable the end- loading of submarines. End-loading construction processes develop hulls with better circular geometry and stability (both critical features in a submarine) than those built by bottom-up traditional methods. For years, EBQP increased the amount of modular construction within its overall process. The scheduling was easier, and the quality and ease of assembly and integration have substantially increased. Metrics indicated a minimum rule of 3:5:8 in cost. This means that an operation costing $3 to perform on the shop floor at the part level, will cost $5 to perform at the modular construction phase, and will cost $8 to perform when done in the hull. The earlier an operation can be performed, the less expensive and easier it is to do. Modular construction allows each piece to be welded and assembled in the easiest position and configuration, with all trades working more effectively with almost no rework.
To be more effective, EBQP moved to a completely modular design on the new Virginia Class submarines, which enables modular construction. Parts, assemblies, super pieces, and the overall boat are modeled in CATIA. Detail design layouts including piping, power, mechanical, and other trades are included and optimized by modeling. Load and unload paths, including end loading, are also modeled before actual construction to optimize the layout. End loading is achieved with transporters that lift from below to move, rather than moving by overhead cranes. Units up to 400 tons can be end-loaded, and the subsequent assemblies up to 2,500 tons can be moved. The improvement in tolerances from modular design and construction has significantly eased the integration time for the overall boat to one to two weeks for everything except nuclear components. The final assembly fit within the submarine is within four inches of the hull, and the new deck designs are also independent structures from the hull, permitting quieter operation.
An additional, substantial advantage of the modular design is the flexibility it provides. While most companies automate to enable mass production, EBQP has automated to benefit a business of one-of-a-kind deliverables. Most submarines have only the hull structure and small parts which are repeatable; all other design is customized for each boat. CATIA modeling and modular design and construction principles enabled EBQP to optimize the design before actual construction and substantially streamline the integration.
For more information see the
Point of Contact for this survey.