A system that remotely controls preheating of weld assemblies, as opposed to manually controlling the temperatures with heater bars, will reduce costs and rework associated with overheating. The alpha prototype is shown above. CTC photo
The objective of this project was to reduce labor costs associated with the control and monitoring of weld preheat temperatures and to reduce the risk of overheating non-metallic materials within a weld assembly.
Preheating of welding assemblies is a common practice in shipbuilding. A minimum preheat temperature must be achieved to satisfy welding needs, but the upper limit may be bound by the temperature sensitivity of non-metallic materials that are packaged inside the welding assembly in certain applications. Currently, an operator manually controls the temperatures through the use of percentage timers or by plugging/unplugging the power cord and monitors the temperature by using “temp sticks” at each weld station to determine base metal temperature. With the current system, the assembly is susceptible to overheating, causing damage to the non-metallic material. Rework associated with cleaning and re-applying non-metallic material and addressing damaged weld assemblies causes significant additional cost and schedule delays.
NMC developed a prototype remote welding preheat control system to control the preheating process in a production environment. The prototype system can be modified and expanded for production use. The platform targeted for this project is the CVN 78 Class aircraft carrier.
Implementation of a remote welding preheat control system could reduce the cost to monitor and adjust preheat and interpass temperatures by an estimated $820K per hull. Also, the risk of damaging weld assemblies and the resulting cost and schedule impacts could be reduced.
The developed system did not meet all of the project requirements. Since more precise control would be required to permit implementation and the cost of the system would approach that of competing systems, NMC recommended expanding the use of an induction heating system. While implementation will not occur at Huntington Ingalls Industries - Newport News Shipbuilding, General Dynamics Electric Boat is interested in a slightly different application. NMC is investigating this alternative application.
General Dynamics Electric Boat Corporation
Naval Surface Warfare Center, Carderock Division
Newport News Shipbuilding
PMS 378 Future Aircraft Carriers