Underwater Welding

Underwater welding is used for repairing ships, offshore structures including oil drilling rigs, and pipelines that are submerged in water.

Taking out the damaged components from the sea for repair purposes is a costly and time-consuming task. Hence, to save time and money, underwater welding is preferred for the repair works (wherever possible)

Russian metallurgist Konstantin Khrenov invented it in 1932. However, British Admiralty – Dockyard performed the first-ever underwater welding for sealing their leaking ship rivets.

‘Van der Willingen’ of Holland developed first waterproof electrodes in 1946

Underwater welding is carried out at elevated pressure. Due to high pressure, the welding processes behave differently like changing of arc behavior, increase in arc voltage with an increase in pressure, etc.

Types of underwater welding:

Underwater welding can be categorized into two types, these are the following;

  1. Wet underwater welding
  2. Dry underwater welding (also known as hyperbaric welding)

Wet underwater welding:

As the name suggests, it is carried out directly in the water itself. Hence, the welder is completely exposed to the water and the surrounding elements.

Shielded Metal Arc Welding (SMAW/MMAW) or stick welding with a waterproof electrode is the most commonly used welding process in these conditions.

A constant current welding machine is used for this operation. Direct current (DC) at 300–400 Amps used to power the electrode during these conditions.

The electrode holders of SMAW or stick welding are heavily insulated and designed for water cooling.

A heavy-duty isolation switch is installed in the welding cable to disconnect the welding current when not in use. The welder gives the necessary instructions to the surface operator connect/disconnect. The current always remains disconnected when not in use.

Other welding processes that could be employed during these conditions are;

  • Flux-Cored Arc Welding (FCAW)
  • Friction welding.

The temperature is very low, especially at greater depths. Hence, the risk of welding failure due to rapid cooling of the molten weld pool may not be avoided. Low carbon equivalent steels can give good results, especially at greater depths, because of hydrogen-caused cracking.

Dry underwater welding:

It is also known as hyperbaric welding. An especially constructed enclosure or chamber (also known as habitat) is used to surround the component to be welded and the welder.

The chamber must be sufficient to accommodate the welder as well as the component to be welded. A mixture of gases (typically a mixture of helium and oxygen, or argon) is used to prevent water from entering through the openings.

Following welding processes may be used for dry hyperbaric welding;

  • Shielded metal arc welding (SMAW) or stick welding,
  • Flux-cored arc welding (FCAW),
  • Gas tungsten arc welding (GTAW) or TIG welding
  • Gas metal arc welding (GMAW) or MiG Welding
  • Plasma arc welding (PAW)

However, Gas tungsten arc welding (GTAW) or TIG welding is most commonly used during these conditions.

Quality of underwater welding:

Dry hyperbaric welding often gives good weld quality as compared to wet welding, due to a better or increased control over the physical conditions. Hence, dry welding is preferred over wet welding especially when the quality of the weld is of utmost importance.

Moreover, heat treatments (Preheat or post heat) operations are also possible during dry hyperbaric welding.

Non-destructive tests are also employed out to check the quality of welds as per requirements.

Classes of welds:

The weld metal properties vary with pressure and cooling rates. Hence the underwater weld metal properties usually differ from the welds made above water.

The American Welding Society (AWS) publishes a code AWS D3.6 for Underwater Welding. This document defines three weld classes, these are;

1. Class A weld

2. Class B weld

3. Class C weld

4. Class O weld (discontinued from 2010)

The following organizations develop underwater welding standards;

  • American Society of Mechanical Engineers (ASME)
  • American Welding Society (AWS)
  • Det Norske Veritas
  • Bureau Veritas
  • International Institute of Welding

Underwater welding salary:

Underwater welding career is very lucrative and the opportunities are unlimited. They work in the construction, surveying, and repair in both fresh- and saltwater.

The salary of an underwater welder is determined by the following:

  • Their Employer
  • Their Location
  • Depth of the dive
  • Previous Experience

However, the annual salary for underwater welders may start at $20,000 per year but it may go as high as $300,000 per year.

Underwater welding dangers:

  • Electric Shock: During wet underwater welding, Chances of electric shock may not be avoided due to the presence of water. In SMAW. An electric arc is generated which produces the necessary heat for welding. During the generation of arc, shielding gases are produced which prevents the molten weld pool from coming in direct contact with the water. The electrode holders are heavily insulated and heavy-duty isolation switches are used to prevent any unwanted shocks.
  • High differential pressure: As depth increases, the water pressure increases. However, the biggest danger is the differential pressure also known as “Delta P” (ΔP) hazards. Which occurs when two water bodies intersect each other with a different water level, such as a dam. Due to the difference in depth, Water tends to fall from one body to the next with great force and hence pressure difference is created. Which is undetectable and tough for the diver to escape.
  • Diving risks: During diving, the welder may be subjected to hypothermia, drowning and decompression sickness also known as “the bends”.
  • Explosion: The pressurized gases in a dry chamber or habitat may create erratic arc behavior, which increases the risk of electric shock or explosion.

There are about 10-15 deaths per year due to drowning and electrocution.

Underwater welding certifications:

Primarily the underwater welders must be having a commercial diving certificate and should be a certified welder.  The required certifications may be the following;

  • Welding certificate
  • Diving Certificate
  • Riggers Certificate
  • Safety Certificates
  • NDT certificates

The AWS D3.6 (Underwater Welding Code) is an internationally recognized code for the welding of structures underwater in both wet and dry environments.

How to become an underwater welder:

To become an underwater welder, these are the following minimum requirements;

  • High school diploma or GED
  • Ability to swim
  • Commercial Diving Certification
  • AWS Certified Welding Training

First, you must attend a commercial diving course. After becoming a successful commercial diver, you can work as a diver tender or apprentice diver with a diving company, which provides welding services also. During that, you can get underwater welding training necessary to pass the qualification tests per ANSI/AWS D3.6. After passing the qualification exam, you can become an underwater welder.

Underwater welding videos:

Here are some of my favorite videos on underwater welding, which you may like;

 

 

 

Sandeep Anand

I am a Mechanical Engineer with more than ten years of work experience in the field of welding and NDT.

2 thoughts on “Underwater Welding

  • July 25, 2020 at 5:57 pm
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    I was looking for information regarding underwater welding when I came to your article. I want to say that it is a very comprehensive article for underwater welding. It helped me a lot in my assignment.

    Reply
    • August 3, 2020 at 2:45 pm
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      Thank you

      Reply

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