Underwater Welding : Joint Fit-Up
Since most underwater tasks are more cumbersome than similar topside work, the proper positioning of large members or plates underwater for welding is also quite difficult. Positioning and fitting must be done with thoroughness and care to ensure a satisfactory weld. In underwater fillet welding, it is important that there be no gap at the root of the fillet before welding.
When the gap cannot be eliminated entirely, it should be as small as the conditions will permit. For best results, a patch that is to be welded to a hull plate should be accurately flared to the contour of the hull plate before final fitting in place by the diver. Even the most expert welding is ineffective when the fit-up is poor. It is better to spend a little extra time fitting than to spend a lot of time welding.