Dry areas can be created underwater to allow welding to be done. Welding without this can be done but it needs waterproof equipment and carries more risk.
Underwater welding uses similar welding processes to welding on land, but the environment needs much more consideration. While techniques are the same, the way a weld is completed will vary and there will be more danger when welding underwater.
There are two methods for underwater welding: dry welding and wet welding
We’ve all seen pictures of welders in diving suits, with their welding torch underwater. This is essentially wet welding. The process is similar to normal welding, but it does require a specialist welding rod.
Wet welders usually use shielded metal arc welding, although flux-cored arc welding and friction welding are also used. When the welder is ready to begin, his team will turn the current on. The danger of electrocution is prevented by the bubbles created by the flux, as these act as a shield between the electricity and the water. Direct current is also used instead of alternating current.
- Cheap and quick
- Creates high tensile strength
- Provides easy access to the weld spot
- No need to construct a dry habitat
- Welder must have some diving experience.
- There is a chance the weld may cool too fast and crack
This is a more complex method and involves the use of chambers to keep the area dry. It is also called hyberbaric welding.
This involves creating a dry environment around the weld.
Dry welding use four different welding techniques.
- Habitat welding. This involves creating a sealed chamber around the weld. The water is forced out by filling it with a mix of helium, oxygen and argon, and is then pressurised to the right depth. Two welders will then be lowered in a diving bell and swim in to the chamber to complete the weld.
- Pressure welding. This uses an explosive force or friction to join the metals together under high pressure.
- Dry chamber welding. This is a chamber designed to cover the head and shoulders of the welder. They enter the chamber from below, and with their head and shoulders covered, they can complete the weld.
- Spot welding. These are small chambers, about the same size as a human head. The chamber is placed over the weld spot to keep it dry and is sealed to prevent water from entering. The electrode is then inserted in to the chamber for the weld.
Dry welding can be done using shielded metal arc welding, flux-cored welding, TIG welding, Mig welding or plasma arc welding.
- Provides the welder with better safety.
- Creates a dry area to complete the weld safely.
- Has a better weld quality
- Can be monitored from the surface
- The habitat chamber can be used by multiple welders
- Due to the fact that dry areas need to be created, dry welding is more expensive.
Dangers of Underwater Welding
As with all welding, there are certain dangers involved with underwater welding, but they are a little different to welding on dry land.
- This can occur if scuba equipment fails, or if a diver is caught with the force of water pressure as it rushes to fill a space.
- Working with gases can cause explosions, particularly if hydrogen and oxygen mix together in pockets.
- Electric shocks: Wet welding in particular combines electricity and water so if the correct equipment isn’t used, or is faulty, there is a real risk of a nasty electric shock. Equipment must be waterproof and electrodes must be cleaned. Using direct current can also help avoid this.
- Decompression sickness: If you are working in a hyperbaric chamber, this needs to be correctly pressurised or you could get decompression sickness. Wet welding can also cause this if nitrogen bubbles form in the blood stream.
- Water is cold and working in cold conditions for several hours, can lead to a drop in body temperature.
- Marine creatures: This may sound drastic, but sharks and other dangerous aquatic wildlife do need to be taken in to consideration when preparing for an underwater weld.
Essential Safety Precautions
There are some precautions you can take if welding underwater.
- Keep yourself tethered to the surface. Just as a diver would be.
- If possible, take another welder with you. They can assist and make the process quicker or simpler or help with any problems that arrive.
- Maintain communication at all times.
Frequently Asked Questions:
Do you need diving experience for underwater welding?
Yes, you do. As well as being an experienced welder, you will need to be trained before you can carry out underwater welding. As well as being able to dive, you will need to understand the safety procedures involved and how to weld as part of a team. There are courses available and it’s advised not to attempt to weld underwater without the correct qualifications.
Do you need to make any special adjustments for underwater welding?
As the preferred option is dry welding, you will most likely use the same fillers and equipment as you would with a normal weld. As you will be diving to your weld, even a dry one, it may be an idea to find a way to waterproof your equipment so that it isn’t damaged.
Is there a limit how long you can stay underwater?
Yes, there is. The depth you are welding combined with the temperature of the water means the time spent welding will be strictly controlled, even for a dry weld. That said, underwater welders can spend several hours at a time underwater.
Underwater welding is a specialist skill. While the actual welding itself is the same, there is far more to it than a normal weld.
Anyone who wants to weld underwater needs to understand diving techniques, and all underwater welds will need to have a detailed plan in place to keep risk to a minimum. If you need any welding to be done underwater, you’re advised to consult an expert, rather then try to attempt it yourself.