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When something below the waterline breaks, the first thought is dry dock. But for many kinds of damage a Diver can do the repair while the ship stays afloat. Underwater repairs and welding in Nagoya Port are an option worth considering, as long as it is planned properly.
Wet welding is done directly in the water with special electrodes. It is quick to set up and suitable for many temporary repairs, such as attaching a doubler plate, fixing a small crack or securing a fitting. Dry welding, sometimes called habitat or cofferdam welding, is done in a sealed chamber from which the water is removed. The joint is better, and the result is closer to a workshop weld. It takes longer to set up.
Underwater welding on a ship's Hull needs the approval of the class society. The surveyor will want to see the repair plan, the welding procedure, the welder's qualifications and the extent of the work. He may accept it as a temporary repair, with a time limit and a requirement for permanent repair at the next dry-docking, or as a permanent repair in some cases. We work with ClassNK and ABS requirements and prepare the paperwork the surveyor needs.
The first step is an inspection. The Diver films and measures the damage and records the thickness of the plate around it. The surveyor and the owner then decide on the approach. We prepare a plan with the method, the materials, the duration and the safety measures. The Ship's Draft and loading condition may need to change if the damaged area is near the waterline.
Underwater welding uses electrical current in water, so equipment and procedures must be exact. We use certified equipment, isolation switches and a trained Diver and supervisor team. The ship's own electrical and cathodic protection systems may need to be switched off. Hot work permits and gas checks are required where there are tanks behind the damaged plate.
Welded patches, doublers, small crack repairs, attachment of anodes and pad eyes, and repair of fittings are all common. Large structural repairs, repairs in way of fuel tanks and damage that affects the ship's strength usually need a dry dock. We say so clearly and do not push a repair that should not be done afloat.
At the end you receive the video, photographs, welding records and a written report. These go to the surveyor and the owner and form part of the ship's repair history.
Quality control is harder in the water than in a workshop. Visibility, current and temperature all affect the weld. This is why class societies often treat underwater welding as a temporary repair. A good plan lays out how the work will be tested, for example by visual inspection, magnetic particle inspection where possible, or ultrasonic checks. We describe the testing in the plan and report the results to the surveyor.
A simple doubler plate may take a day. Dry welding in a cofferdam takes longer. Prices depend on the size of the repair, the depth and the materials. We give a written estimate after the inspection dive.
Q1. What is the difference between wet and dry underwater welding?
Wet welding is done directly in the water and is quick to set up, suitable for many temporary repairs. Dry welding is done in a sealed, water-free chamber and gives a better quality joint but takes longer to prepare.
Q2. Does underwater welding need class approval?
Yes. The surveyor reviews the plan, the welding procedure and the welder qualifications. Many underwater welds are accepted as temporary repairs with permanent repair at the next dry-docking.
Q3. What repairs are commonly done afloat?
Doubler plates, small crack repairs, attaching anodes and pad eyes, and repairing fittings. Large structural repairs usually need a dry dock.
Q4. What safety measures are used for welding in water?
Certified equipment, isolation switches, a trained Diver and supervisor team, hot work permits, and switching off the ship’s cathodic protection where required.
