There are three key tools that make up underwater welding equipment, whether “wet” welding, which takes place underwater, or “dry” welding, which occurs inside a hyperbaric chamber. These three are the diving hat, water resistant electrodes, and the hyperbaric chamber itself. A diver will also use several other associated tools and pieces of equipment to do the work efficiently and safely.
Underwater Welding Equipment
A diving hat is a hybrid of a standard scuba mask and a traditional welder’s mask. It looks like an old-fashioned deep-sea diver’s helmet. Welding underwater requires tremendous physical strength, agility, and a clear view of the working surfaces. Construction divers also need to work uninterrupted without having to adjust diving equipment or worry about running out of air.
Instead of tanks, most underwater welders use a full-head helmet that seals to the wetsuit with air lines running to the surface. It’s heavy enough to protect the diver in case of accidents and provides good visibility. Diving hats include a flip-up welding shield to protect the diver’s eyes, just as in on-land welding. The shield may also contain a magnifying welding lens for precision work. Equipment associated with the diving hat includes umbilicals (air lines) and breathing air compressors.
Just like welding on land, underwater welding is performed using a variation of shielded metal arc welding, flux-cored arc welding, or friction welding. In each case, a current of electricity is generated to make an arc, which is applied to metal to melt it. One major difference for underwater work is that the electrodes need to be waterproof. Insulation around the connections allows the electricity to generate an arc without damage to the copper wiring.
Maintaining an arc of electricity underwater presents greater technical difficulties than doing so on land, so direct, not alternating, current is used, which also lessens the risk of electrocution. Insulated power cables connect the tools to a power supply on land. These are used with various connectors, meters, and grounding clamps.
A hyperbaric chamber is a sealed space filled with a breathable mixture of helium and oxygen that allows a welder to work in dry conditions. Hyperbaric means “greater than atmospheric” — the chamber is filled with gases pumped in at the prevailing pressure at that depth to accommodate a diver and welding equipment underwater. The quality and precision of the welding done in a hyperbaric chamber are much higher, comparable to work performed on land, and conditions are safer and easier for the diver.
Visibility and flexibility are greater because the diver doesn’t need to wear so much equipment, and s/he can work without interference from water currents or indigenous marine life. The downsides of the hyperbaric chamber are that it is expensive (and costs increase with depth) and time-consuming to build.
In addition to these core elements, underwater welders will use electrode holders, circuit breakers, oxygen hoses and manifolds to connect gas cylinders, torches and other cutting tools, and grinders to prepare and finish the welding surface. Safety equipment necessary for underwater welding includes gas flow regulators, a communication system, and gloves (both heavy duty and surgical). For quality control, welders use leak detection devices, flaw detectors, ultrasonic thickness testers, and dye penetrant test kits.
A trained underwater welder will be familiar with all of these tools and accessories. The list seems daunting, but it all fits together logically, and most of the technology is adapted from air welding and the safety protocols for recreational and commercial diving.