Water works

Welding high-strength steels is never a simple task. But welding underwater, or ‘wet welding’, makes the job even more difficult.

Defence support specialist DML, based at the Royal Navy’s Devonport dockyard, has now succeeded in wetwelding two high-strength steel grades used in submarines, and believes the technique can be extended to other underwater structures such as pipelines and oil rigs.

But wet welding isn’t just welding underwater — it’s manual arc welding without anything to protect the metal, such as a hyperbaric chamber.

DML has been working on the problem because of the need to decommission nuclear submarines. Wet welding techniques allow this to be done with the submarine in the water, removing the need for dry-docking.

To keep the submarines afloat during the procedure, blanking plates have to be welded on to the aperture of the subs’ ballast tanks to seal them, and that means that high-strength, low-alloy steels have to be welded together.