The term ‘underwater welding’ comes as a surprise to many. This is because welding needs a flame or an arc, either from burning of a gas or from electricity, and water does not go well with the flame/arc. However, underwater welding is quite possible, and it is a serious occupation for highly qualified welders (with some diving background) and a decent pay.
In the late 1910s, the concept of underwater welding came into picture to temporarily fix/repair ships and barges. But later, there has been significant advancement in the technology, equipment, and procedure of underwater welding for constructing and repairing marine structures, bridges, dams, seacrafts, and many more. Underwater Welding saw a noticeable boost with the development of offshore oil and gas drilling rigs, deep sea mining, fisheries, pipelines, etc. Even nuclear power plants involve certain underwater welding tasks.
In this guide, we will explain everything you need to know about underwater welding.
Outline
ToggleWhat is Underwater Welding?
Underwater Welding, as the name suggests, refers to the process of welding underwater, usually under the sea where the pressure levels are significantly higher. performed in a wet environment. Generally, underwater welders are first trained to be professional welders and then trained to be professional divers. This was the trend in the early days of the “profession” that the diving companies saw.
Unlike regular welding, underwater welding is dangerous, but with proper precautions, it is going to be regular work. After graduating from welding school, you need two to three years of work experience with structural welding and pipe welding. With a strong welding background, the welder can join a professional diving school and learn underwater welding and cutting.
Risks and Rewards of Underwater Welding
When you are working under water, there is a chance of electrocution as salt water is a good conductor of electricity. There is a life risk involved if the workers are not careful and follow safety standards strictly.
Since the risk is quite high, the reward is equally high. Underwater welding happens to be one of the highest paid occupations. That is why the employment rate is increasing in underwater welding profession.
The average annual wage happens to be around $60,000. The top ten percent of underwater welders get over $1,50,000 annually. You do not need a college degree to become a professional underwater welder.
What are the Types of Underwater Welding?
There are two main types of underwater welding. They are:
- Wet Welding
- Dry Welding
1. Wet Welding
Wet welding is the “traditional” underwater welding. This means the welding will be done in wet conditions and obviously under water. In Wet Welding, there is no protection for the arc from water i.e., the arc is directly applied in the water.
Shielded Metal Arc Welding (SMAW) or Stick Welding is the most popular type of wet welding technique. The power supply is usually DC and the electrode configuration is DCEN to minimize the electrolysis phenomenon. Special electrodes of sizes 3/32 inch (2.4mm) and 1/8 inch (3.2mm) are used in wet welding.
We can also use larger electrodes of sizes 3/16 inch (4.8mm) and 5/32inch (5mm). But they deposit significantly large amounts of metal and this increases porosity and reduces ductility.
These electrodes comply with the E6013 Classification but with the condition that they are waterproof. The electrode holder is different from the regular holder that we use for normal SMAW. It must also be waterproof.
Depending on the budget and the urgency of welding requirements, wet welding is the most preferred choice. The accessibility of the repairing spots also makes wet welding a suitable choice.
The risk involved with wet welding is higher. But the quality of welding is not as great as dry welding as the welding area cools down quickly due to the surrounding conditions. Naturally, there can be cracks and defects.
Advantages and Disadvantages of Wet Welding
Advantages
- Significantly low-cost process
- We can finish the work very quickly (no need for a chamber or structure)
- Welding workpieces with odd shapes is possible
- Welder can reach any offshore place
- Main welding equipment is nothing special (only the electrode, holder are waterproof)
Disadvantages
- Proper insulation is necessary to avoid the risk of electric shock
- Welder must have both welding as well as diving skills
- Water acts as a heat sink. Reduces the strength and ductility of the weld
- Poor visibility
- Release of hydrogen increases porosity
2. Dry Welding
It may come as a surprise to many but underwater welding can be done in dry conditions. In dry welding, the procedure is done inside a hyperbaric chamber also known as habitats. These habitats are large structures built around the section where we have to perform the welding operation. The environment is safe, and it reduces the chances of inflammation due to gases. This method is widely popular in oil rig where the environment is breathable. Since the pressure inside the chamber is higher than outside, the gases flow outside.
The welder and the equipment can reach the chamber through a tunnel-like structure that extends to the surface
The chambers are highly-pressurized with pressure equal to the water pressure at that depth so that the water stays out. There are several types of dry chambers/habitats for underwater welding. They are:
- One-Atmosphere Pressure Chamber
- Ambient Pressure Chamber
- Open Bottom Chamber
- Dry Spot Welding
- Cofferdam
Another type of dry welding uses a special gas to shield the electrode, workpiece, and shielding gas from water with the help of a cavity or nozzle. In this, the welder is in water (unlike the hyperbaric chamber where the welder is inside a pressurized structure shielded from water) but the workpiece, wire feeder, and the electrode are inside a tiny watertight enclosure.
Advantages and Disadvantages of Dry Welding
Advantages
- No problem of porosity (as there is no release of hydrogen)
- Stable welding operation
- No risk of electric shock
- Good transfer of heat (as the workpiece is shielded from water)
- Ductile strength of the weld is good
- Excellent visibility
Disadvantages
- Very expensive
- Needs special structure as per the shape of the workpiece
Welding Procedures for Wet and Dry Underwater Welding
There are different processes available for performing underwater welding. Choosing the process depends on the type of welding required, skills of the welder, and the budget of the welding. Here are the different processes of underwater welding.
Wet Welding
1. Stick Welding (SMAW)
It is the most common process of wet welding because it is cost-effective and it has versatile applications. An electric arc is created between the consumable electrode and the structure to be welded using power supply. The filler material melts and deposits on the joint or repairing area. The surfaces must be clean for the process to be of high quality.
Before performing the process, the welders ensure safety guidelines. A layer of gaseous bubbles is created during the entire process. These bubbles are due to electrolysis of water and release of hydrogen. Bubbles can be a hindrance in visibility but that is where the skills and experience of the welder come into the scene. Instead of alternating current, direct current is used that too with DCEN polarity.
Dry Welding
For dry welding, we can use any of the following welding processes.
- Shielded Metal Arc Welding (SMAW) or Stick Welding
- Gas Tungsten Arc Welding (GTAW) or TIG Welding
- Gas Metal Arc Welding (GMAW) or MIG Welding
- Plasma Arc Welding
- Flux-Core Arc Welding
Of these, the SMAW is very less popular as the flux-coated electrodes release large amount of smoke and fumes.
1. Gas Tungsten Arc Welding
The Gas Tungsten Arc Welding (GTAW) is an extremely popular and effective welding process. It is also referred to as TIG Welding. It uses a tungsten electrode, and it works under high temperatures.
The process involves an electric arc between a non-consumable tungsten electrode and the workpiece. The arc will melt the workpieces and fuse them together. TIG Welding used shielding gas to protect the weld pool and improve the quality of the arc. We can use TIG Welding for depths up to 100m (330ft).
2. Gas Metal Arc Welding
Another process that is equally popular is the Gas Metal Arc Welding (GMAW) or MIG Welding. MIG involves a consumable electrode to weld the workpieces. A shielding gas is used for better deposition and also protect the pool from contamination. MIG is easier than TIG for any welder.
3. Plasma Arc Welding
This process is similar to TIG. It uses an electric arc between the electrode and workpiece. The difference lies in the fact that the electrode is placed inside the torch body in plasma arc welding while it stays outside in gas tungsten arc welding.
The process is also applicable to wet welding where a hyperbaric chamber is used for shielding and safety purposes. The chamber contains breathable gases, and the diver needs to enter the chamber for welding process.
4. Flux-Core Arc Welding
When you want to deposit metal alloys as the filler material on the joint, flux-core arc welding is the best method. This is because the electrode will have filler material with flux for better welding work. The electrode comes in the form of wires for accurate deposition.
What are the Dangers Associated with Underwater Welding?
We have already stated that underwater welding is quite risky. But there are several such professions available where the risk is equally high as the reward. The risk is very high if you compare underwater welding to traditional dry welding. Here are the dangers in the operation of underwater welding that you should be aware of.
- Drowning: There is a high chance of drowning if any gear fails when the diver is so deep underwater. A backup gear is essential for such an extraordinary situation.
- Combustion: There are certain flammable gases involved in underwater welding such as oxygen. Due to any mishandling and mistake, the explosion can be life-threatening. Proper ventilation is a must to avoid such scenarios.
- Electrocution: The biggest danger in underwater welding is electrocution as the operation involves large amount of electricity. All gears need to be waterproof.
Apart from these, due to high pressure environment, damage to the lung is common if the diver is overworking. Another common health issue is called diver’s disease due to the consumption of gases can be fatal.
Conclusion
Underwater welding is quite common though it sounds something impossible. It is a well-paid professional work where risks are equally rewarding. We have explained all the different types and methods of underwater welding. Moreover, we have stated the dangers of underwater welding that you should be aware.