As mentioned above, there are two basic types of underwater welding; dry welding and wet welding.
In dry welding, a hyperbaric chamber is sealed around the structure to be welded. The chamber is then filled with gas (typically a mixture of oxygen and helium) to expel the water and create a dry atmosphere for the weld to be performed. The chamber needs to be pressurised to the right level to prevent welders from suffering from decompression sickness while working.
However, there are instances where welder-divers don’t have access to a hyperbaric chamber or when urgency means that a repair needs to be done immediately. In these instances, wet welding may be used instead.
Wet welding relies on the release of gaseous bubbles around an electric arc to shield the weld and prevent any electricity being conducted through the water. This insulating layer of bubbles protects the diver but also obscures the welding area, making it harder to complete the weld correctly. The bubbles can also disturb the welding pool and the welded joint may cool too quickly due to heat dissipating through the surrounding water. This increases the risk of defects such as cracking.
Underwater welding uses direct current settings rather than alternating current, as it is safer for the underwater welders to work with.
It is difficult to ignore the inherent risks involved in underwater welding, but these risks are also why underwater welding is one of the most well-paid career options for commercial divers.
Many underwater welders begin by training to become professional welders before learning commercial diving. You should make sure you enrol in high quality training schools to learn both the welding and the diving aspects of the job before seeking further training from an accredited institution to bring the skills together as an underwater welder.
This training can take years to complete, but helps to mitigate against potential dangers, including electrocution and drowning.
A variety of welding processes can be used with both wet and dry underwater welding.
Wet Welding Processes:
Also known as stick welding, this technique is often used for wet welding jobs. With this versatile and cost effective process, welders create an electric arc between the electrode and the structure to be welded. This arc melts and deposits filler material into the joint. The electrodes and the base metal surfaces must be clean to perform this weld properly and the diver should also inspect the area for obstructions or other safety hazards.
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This technique uses a filler material tube with a flux at the core. The electrode wire is automatically fed through the welding gun to allow for accurate and controlled welds. This method is used for materials including cast iron and metal alloys such as nickel alloy.
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Friction welding uses heat and friction to fuse the materials and can be performed underwater.
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Dry Welding Chambers and Processes:
The type of welding method used with dry welding depends on the size of the hyperbaric chamber being used. These include:
This method uses a small chamber and is often used for hot work. Gases are pumped through the chamber continuously to maintain a breathable atmosphere and keeping the pressure slightly higher than the pressure outside. This pressure difference prevents the influx of dangerous gases and combustible hydrocarbons as well as transporting any toxic welding fumes out of the chamber. Larger habitats can accommodate two or three divers at a time.
Pressure welding uses explosive force and/or friction. This broad type of solid state welding includes processes, such as diffusion welding, explosion welding, gas welding, resistance welding, ultrasonic welding, and friction welding, which was invented at TWI in 1991.
Dry spot welding
This method uses small chambers which are placed over the weld area to create a dry atmosphere. An electrode is placed into the chamber to create the weld.
Dry chamber welding
Similar to habitat welding, this method uses a hyperbaric chamber to create a dry atmosphere for the weld. However, in this instance, the chamber is smaller and only accommodates the upper body of the welder.
With regards to processes, dry welders employ shielded metal arc and flux cored arc welding, as with wet welding (see above). In addition, dry welders also use:
Commonly called ‘TIG welding,’ this method uses a non-consumable tungsten electrode to create an electric arc and another wire for the filler material. This technique creates high quality, durable welds but also requires a high level of welder skill and precision.
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Also known as ‘MIG welding,’ this technique uses a welding gun that automatically feeds the filler wire while pumping a shielding gas to protect the weld area.
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Plasma arc welding uses an electrode to create an electric arc. This electrode, usually made from sintered tungsten, is located in the body of the torch to keep the arc away from the inert gas. Plasma is injected through the copper torch nozzle at high speeds, creating extremely high temperatures. The nozzle is used to restrict the plasma in one direction to create accurate welds.
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Welding is commonly used for a range of offshore and marine applications. Given the difficulties and dangers of underwater welding, much of this work is carried out in shallow waters or by moving structures to dry areas first.
However, welding structures at greater depths can save the cost of removing a structure from the water, as well as dry docking costs. Underwater welding not only allows for these cost savings, but can also be used to effect emergency repairs.
Used to weld fully or partially submerged marine structures, underwater welding is used on ships, dams, oil rigs, pipelines, bridges and more. Underwater welding techniques are also used in applications related to nuclear power stations, rivers, canals, and more.
How much does an Underwater Welder Make?
Due to the dangers associated with the job, underwater welders can make a very good annual wage. The actual wages are determined by factors including experience, certification, location, working environment, depth of work, distance from the shore, dive methods and equipment used and more. Statistics show that the salary ranges can vary dramatically, from around £25,000 per year right up to over £230,000 per year.
How to Become an Underwater Welder
To become an underwater welder you need to be an expert diver, which will usually mean passing a course at a commercial diving school. This will not only teach you diving skills, but will also cover underwater safety and emergency procedures. As well as passing dive school, you will also need to be a certified welder. With these skills under your belt, you will then need to pass a special underwater welding course to learn about the specific tools and techniques associated with the job. This training can take years to complete.
Is Underwater Welding a Good Career?
Underwater welding can be a very lucrative career, but it also requires a lot of training and can be dangerous. As a result, many underwater welders invest their earnings so they can retire early.
Why is Underwater Welding so Dangerous?
Underwater welding is more dangerous than land-based welding as it is performed in environments that bring extra safety factors into play. These include gas pressure, water pressure, diving equipment, working in restricted spaces, power supply, and more. In addition, underwater welders are often required to work in remote and potentially dangerous offshore locations such as oil rigs and subsea pipelines.
Despite the financial rewards, underwater welding is one of the most dangerous jobs you can do, with drowning, explosions, and electrocution being very real hazards, along with long term health issues related to your nose, lungs and ears if too much time is spent working deep underwater, decompression sickness, and attacks from marine wildlife!
What is the Death Rate for Underwater Welding?
The main causes of death for underwater welders are drowning and decompression sickness, with investigations placing the fatality rate among underwater welders as high as 15%. This is the highest death rate of any profession, and you can compare this to a death rate of 0.2% among those working in logging or fishing.
Underwater welding can be broadly split into dry and wet welding techniques. Dry welding, which uses a hyperbaric chamber to create a dry environment around the weld area for the welder to work in, offers better results than wet welding, which uses the bubbles created by the shielding gas to cover the weld area.
Underwater welding is a lucrative and necessary, yet dangerous profession. The techniques used for underwater welding are used for repair of marine structures and assets including offshore pipelines, oil rigs, and ships. Underwater welders also work in places such as nuclear power plants.