Navy underwater trials completed in TWI tank

Connect, no.101, July-August 1999, p.7

Underwater butt welding trials, designed to demonstrate to the Ministry of Defence the feasibility of sub-sea ship repairs, have been successfully completed in TWI North's diving tank.

For several decades the Navy has used underwater welding for temporary repairs to damaged vessels. If those repairs could be accepted as permanent, the costly and time consuming business of dry docking could be avoided.

A large panel, simulating the damaged side of a ship, was lowered into the TWI tank. Simulated patch areas were cut out underwater using two processes, thermic lancing, a fast technique which leaves a rough edge, and the slower but more refined technique of water arc gouging.

'The sides were tidied up using an underwater grinder and prepared with a wide enough root gap to deposit two beads against a previously positioned backing strip', project leader David Abson told Connect. 'A template of the patched insert was prepared underwater, the patch plate cut to size, and then clamped in place using four temporary dogs. Several hours of wet welding completed the job'.

The finished repair was sectioned and investigated radiographically, mechanically and metallurgically at Great Abington.

	The patch plate being welded into place
	The finished article ready for investigation at Great Abington

Copyright by TWI, 1999