Welding Technique Helps Navy Save Millions
When maintenance welding required cutting into the hull of a Navy submarine, John Bartly knew there had to be an easier way. Mr. Bartly supervises 15 welding engineers as a U.S. Navy employee on Mare Island in San Francisco Bay. A former president of the American Welding Society, he has decades of experience.
He and his engineers approached Hobart Lasers & Advanced Systems in May 1990 (formerly Martek) to create a multi-faceted program which would meet several welding challenges he faced in his assignment to repair Navy submarines and other seagoing vessels. To date, Hobart has evaluated equipment, developed accessories and conducted feasibility studies on a number of innovative processes for the Navy. Hobart's Application Development Centers provide an opportunity to test applications on state-of-the-art CW Nd: YAG lasers; Orbitig control systems; Viper tube-to-tube welding heads; HAWCS computer-controlled variable polarity plasma/gas tungsten arc systems; and other equipment. A challenge Mr. Bartly faced was the repair of deteriorated valve seats on the steam chest, which contains control valves to throttle the submarine's steam flow. Conventional welding processes in these applications are low yield and must be repaired several times. The low power density process required Mr. Bartly's welders to cut through the pressure hull of the sub, remove the item to be repaired, take it to the shop, preheat it, manually repair the item, post-weld heat it, machine it, return it to its original position, and repair the opened pressure hull. To cut down on this process, saving time and money, Hobart's engineers found that by using laser technology they could perform the repairs without having to remove the component, as the preheat and post heat are not required. "Because it has a 150-ft.
(45.7-m) fiber optic delivery system, our 2,400-watt CW Nd:YAG laser welding head can be brought internal to the vessel and locally tooled with accessories, potentially saving millions of taxpayer dollars," said Tim Webber, a Hobart Laser Applications manager.
In repairing the steam chests, old material must be machined off and replaced to a precise finish, size and polish. Currently, Hobart is developing a system with a small articulated gantry robot, small enough to get in the operator's lap. Using rotary motion, the robot welds a hardface alloy place from a small mechanical bridge. A pendant-like controller is used by the operator at the welding site to set up parameters as necessary. The laser generating equipment sits outside the vessel.
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