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What is underwater welding? The Surprising Technique to Bind Metals

Welding is a challenging task. But it becomes more challenging when a welder is exposed in a more difficult situation. Welding underwater! Is it humanly possible? Certainly, yes.

However, you have to work against many things, including the pressure of water and some visual difficulties.

Nevertheless, underwater welding has diverse applications. Without this kind of welding, probably, we wouldn’t have any ships. But without this welding type, it is sure that the majority of large-sized ships won’t be repaired quickly.

We’re not through yet.

Repairing pipelines, dams, sub-sea habitats, locks, oil drilling rigs, etc., depend on this kind of welding. So, no one can underestimate the importance of underwater welding.

Now:

Most people have a basic understanding of welding. But how exactly is welding underwater done? Before we look at details, two things are certain:

First, welding underwater has excellent considerations for your safety, and,

Second, you need to be a good diver for you to work effectively, especially if you are working on marine infrastructure.

WHAT IS UNDERWATER WELDING?

Underwater welding simply means the process of binding two pieces of material underwater or places with elevated pressure.  The process is divided into two i.e.

  • Wetwelding – taking place in water and
  • Dry welding –taking place in a special enclosure with positive pressure.

In the latter process, you work in a rather dry environment. This kind of welding is also called hyperbaric welding, primarily when used in a dry environment.

Much as welding underwater is not very different from welding on land, having a successful high-quality weld underwater requires creativity.

Simply put,

An underwater welder is a certified welder but has additional knowledge and skill set required to work in below water conditions. Attaining these skills takes a long time and requires additional certification from commercial dive schools.

DANGERS

Underwater welding is, without a doubt, a profession that requires specialized training and skills. Besides, it is difficult for you to work in such circumstances if you don’t have a great deal of courage and an adventurous sense.


Welding underwater comes with a lot of hazards, and some are inescapable ones.


Major risks include:


  • Drowning in cases where the equipment fails: This usually occurs in case of differential pressure or Delta P hazard.
  • Sickness, e.g. decompression (buildup of nitrogen in the bloodstream) and hypothermia (body temperature goes below average due to working in cold conditions for long). 
  • The danger of electric shock – familiar with an inexperienced welder who doesn’t use DC as power supply.
  • Underwater explosions – common when hydrogen and oxygen mix and built up in pockets.

Other problems might include hearing problems, muscle ache, and loss of cognitive function, for welders who have worked under water for a considerably longer time.


Statistics from OSHA indicate that reported fatalities are between 6 and 13 in a year in a population of about 10000 workers.


Good news is, technology is advancing, and so are the safety protocols. This will most definitely reduce fatalities in the future. Besides, the likelihood of an accident occurring is mainly dependent on the training, equipment, and supervision provided by the employers.

TYPES OF UNDERWATER WELDING

1. WET WELDING

This is welding in open under water and utilizes the techniques of SMAW and FCAW. Also, it may involve the use of self-shielded FCAW.

The process of welding breaks down water into its constituents – hydrogen and oxygen. This makes the surrounding area to have high amounts of hydrogen and oxygen. These compounds are very detrimental to the mechanical features and integrity of a weld.

The welds that are produced in this type of welding are subjected to higher cooling rates. This translates to higher currents amounts needed to compensate for the quenching effects, a feature that might cause undercutting.

Basically, Underwater welding usually results in welds that are highly porous due to the molecular hydrogen, water vapor or carbon monoxide. As such, the welds are highly defective, less ductile and suffer from hydrogen embrittlement (hydrogen penetrates the weld pool). When cracks occur, they might propagate to the parent, causing severe damage.

Note that wet welding is usually done based on the accessibility of the welding area as well as the severity of the repair needed.

2. DRY WELDING (HYPERBARIC WELDING)

Underwater welding can be done in a dry habitat too. To achieve this, a dry chamber is usually used or a hyperbaric chamber. Here, water is replaced with by a mixture of gas. Such a chamber can hold up to 3 welders at a go. 

Dry welding is a preference for wet underwater welding, especially if welders need high-quality welds. 

With dry welding technique, you can achieve much control over conditions you require for welding hence higher performance.

However, with increasing depth, pressure increase. This causes a higher cooling, which substantially increases the tendency to crack. Note that increased pressure makes the welding arcs unstable. But research is underway to give better results.

WHAT TYPEs OF WELDING are USED UNDERWATER?

There different types of welding used underwater. Some techniques overlap in wet and dry welding.

Wet welding

  • Stick welding/shielded metal arc welding (SMAW) – cost effective as well as a versatile method to produce an r between the electrode and metal.
  • Flux-cored arc welding (FCAW)–use a continually fed filler metal to weld nickel alloys and cast irons.
  • Friction welding (FC)–use high friction and heat to fuse metals.

Dry welding

  • Pressure welding –applied in pressure vessels.
  • Habitat welding – involve the use of a room with ambient pressure.
  • Dry chamber welding –covers the head and shoulder of the welder-diver.
  • Dry spot welding –a small clear chamber placed on the welding site.

The standard method includes; SMAW and FCAW.

Other welds are;

Gas tungsten arc welding, plasma arc welding and gas metal arc welding (MIG).

CONCLUSION

Underwater welding is dangerous but necessary. If done correctly, the accident can be reduced. Safety precautions include tethering yourself to the surface, constant communication, proper supervision, and help. 


Note that technological advancements are underway to protect the Diver-welders. In fact, robots are being manufactured to help in that process, but until then, humans will dive deep in water to maintain the integrity of marine structures.


No one can deny the fact that this is one of the riskiest and challenging jobs, both mentally and physically.  Though not one of the most lucrative careers in terms of working condition, it is a sure way to make good money.

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