How Underwater Welding Works

Many people have never heard of underwater welding. That’s not surprising since electricity and water are incompatible and can pose an extreme danger when they meet up. However, underwater welding, also known as hyperbaric welding, is more common than you might think.

It was first used in the 1930s and is still used today to repair or maintain submerged marine structures. For example, some hyperbaric welders work inland on bridges, dams, and small seacrafts. Others work offshore on oil rigs, pipelines, and ships. They could even do hyperbaric welding on nuclear power plants.

For those who think underwater welding sounds dangerous, they are right. It is pretty scary, making it a highly paid occupation with an average salary of nearly $55,000 annually. If that whets your appetite for a lucrative welding career, here is what you should know:

There are two basic types of underwater welding

Dry welding: An underwater welding process called “dry welding” might sound like an oxymoron. But, it entails using a hyperbaric chamber that provides a dry, controlled environment in which the weld is completed. The more common of the two types, dry welding offers higher quality and reliability, not to mention increased welder safety. Another advantage is being able to perform non-destructive testing in the dry chamber.

However, wet welding has a few disadvantages, including its extremely high cost and the complex equipment needed both in the chamber and on the surface.

Wet welding: When the cost of dry welding is prohibitive, wet welding is the chosen alternative. Besides being less expensive, welders can reach portions of an underwater structure that would not be accessible using a chamber. Since there is no time consumed gathering all the equipment and building the chamber, wet welding is a faster process, making it ideal for emergency repairs.

On the downside, there is more risk involved from welding in the water. And because the weld could cool too quickly, the risk of cracks and joint defects, such as porosity, decreased ductility, and less impact strength. The poor visibility with wet welding can also make it difficult to weld correctly.

How underwater welding works

With dry welding, the hyperbaric chamber is lowered to the weld area, and a seal is created before the water is pumped out and replaced with a gaseous mixture, such as helium and oxygen. The chamber is pressurized at the correct level, preventing decompression sickness. At that point, the welder/diver can choose the appropriate welding technique:

• Habitat welding: This method involves welders operating in a small chamber (habitat). Typically employed in offshore oil rig welding, habitat welding creates an environment that minimizes the threat of combustion from flammable vapors and gases by pumping in gases continuously and maintaining a breathable atmosphere.
• Pressure welding: Here, welding operators employ an explosive force and friction to join the components under high pressure. Also called ultrasonic welding, resistance welding, diffusion welding, and friction welding, they all have one thing in common: they use mechanical pressure at the weld area to join the sections.
• Dry chamber welding: With dry chamber welding, a small chamber accommodates only the upper body of the welder. The diver must enter the chamber from below, and the chamber covers the head and shoulders only.
• Dry spot welding: Dry spot welding also works with small chambers. The chamber is positioned on the welding area to create a dry welding environment while the diver works within it. A tight seal is required to keep out the surrounding water.

In dry welding, shielded metal arc welding (a.k.a. stick) and flux-cored arc welding are often used. Other methods include gas tungsten arc welding (TIG), gas metal arc welding (MIG), and plasma arc welding.

For wet welding, stick welding is a popular option because it’s inexpensive and versatile. Welders use a consumable electrode energized by a power source. An arc is created between the electrode and metal, causing the filler material to melt and enter the joint. For this welding process to be effective and safe, the electrode and base metal must be clean.

So, why isn’t the diver electrocuted by the current? The fundamental answer is that the layer of gaseous bubbles generated when the arc melts the flux shields the weld and prevents electricity from being conducted beyond itself. In addition to stick welding, flux-cored arc welding and friction welding are options for wet welding.

How does underwater welding differ from land-based welding?

Although there are many similarities between welding underwater and on land, the danger factor sets them apart. Because there are so many variables complicating things underwater—water pressure, gas pressure, diving equipment, restricted space, power supply, and more-- welders face excessive dangers underwater compared to on land.

Even though this work is financially rewarding, it is also one of the most hazardous jobs, with a fatality rate among the highest in all occupations. Some of the dangers include:

• Drowning
• Explosions
• Electric shock
• Electrocution
• Lung, ear, and nose damage
• Decompression sickness
• Marine wildlife attacks

Despite the dangers, underwater welding appeals to adventurous welders looking for top pay and a challenging career.