Understanding Wet Welding Methods

Underwater welding is conducted under elevated water pressures. It can be classified into two categories: wet welding and hyperbaric welding. Wet welding occurs in the water itself, while hyperbaric welding is conducted in a constructed pressure enclosure in a dry environment.

Let us dive into how wet welding works (pun intended).

Wet welding is a process carried out using a waterproof stick electrode, as there’s no physical barrier between the welding arc and water. The welding power supply is located on the surface level with connections made to the divers or welders using cables and hoses.

Science of wet welding

For underwater wet welding, alternating current (AC) isn’t used due to electrical safety standards and difficulty maintaining an arc underwater. For this reason, direct current (DC) is employed using positive polarity where electrolysis runs from the stinger, through the electrode, and onto the workpiece.

Applications of wet welding

Wet welding has some critical applications in the offshore and inshore construction industries for maintaining underwater pipelines, jetties, and piers. In addition, the methodology can also be utilized for the repair and maintenance of ships in the event of a collision or accident.

Equipment required for wet welding

Adequate equipment is required for underwater wet welding for it to comply with safety protocols. These are some of the main equipment’s needed to ensure proper functioning:

1. Communication system

Two-way communications must be applied for constant connection and coordination of underwater activities between the diver and surface.

2. Diving equipment

It is imperative to deploy specialized equipment which fully supports surface-supplied diving operations. This includes a diving umbilical and hard hat diving dress, gas panels, welding shields, and CCTV recording suite. It is also vital that the correct breathing medium be used relative to the depth of the job. Compressed air would be used on shallower work, while complex gas mixtures would be implemented for the deep stuff. A hyperbaric chamber may be necessary to be on-site on deeper wet welding projects that require decompression diving.

3. Mechanical tools system

Mechanical tools may be driven electrically, hydraulically, or pneumatically for underwater works. To ensure maximum safety, electrical tools are avoided, and hydraulic and pneumatic tools are used.

4. Welding power sources

An intensive rectified power source is crucial to obtain a stable electric arc even in great depth while maintaining the maximum safety redundancy.

5. Welding cable plus welding and cutting holders

Special insulation class cables must be used for welding and cutting to prevent the leakage of an electric current into the water.

6. Safety switch

The electrical circuit must be integrated with a safety switch known as a “knife switch” to interrupt or establish current flow.

The benefits of wet welding

The advantages of employing an underwater wet welding technique compared to other welding methods, such as dry welding, are that it costs less, and it’s a much faster method that makes it highly desirable.

Minimal equipment is required for mobilization, and the welder can reach portions of the ship or offshore structures that couldn’t otherwise be welded using external methods. Besides, no time is lost in surfacing or dry-docking, as the welding can be done on-site while the structure remains underwater.

Thai Subsea Services is an underwater ship service provider in Thailand. They offer ship maintenance services such as ship and boat hull cleanings, propeller polishing, and subsea welding. They also provide ship repair services and offshore commercial diving services.