Our underwater infrastructure that supports our daily lives requires the specialized skills of heroic commercial scuba divers.
Commercial divers that are responsible for maintaining underwater systems perform a very dangerous , but needed job that makes everyday life as we know it possible.
They are often exposed to working under enormous water pressures with limited visibility to maintain or repair our pipelines, oil rigs, nuclear facilities, dams, bridges…etc.
In most instances they are required to do underwater welding in limited visibility well below the surface. Hyperbaric welding is the term used to describe welding under high pressures.
This type of welding can be done in the water (wet welding) or within hyperbaric chambers (dry welding) designed to keep the water out as explained below.
The wet welding technique is used as a temporary solution in emergency situations. The wet welds can cool down too quickly by the water thus increasing the chance of cracking. Mostly done in hard to access areas, wet welding requires working in severely dark and cold environments with minimal visibility.
Just like the conventional welding, underwater welding also uses electricity as the energy source. The technique most commonly used under water is the stick welding that uses an electric arc. In the case of wet welding, the flux on the outside of the rod creates bubbles when it evaporates. These bubbles form a gaseous layer over the joint protecting it from oxidizing agents.
Read for more details here on wonderfulengineering.com
Watch the video below for a glimpse at how it is done
The Hazards of Underwater Welding
As hazardous as it may seem to be to perform these tasks below the surface, the real hazard has to do with what is called Delta P. Delta P is a term that is used to describe the tendency of water to equalize pressure between two connected bodies of water. Often times these commercial divers can find themselves dealing with enormous forces caused by water at different pressures that is trying to equalize.
See below for more details on how easily Delta P can occur on commercial diving jobs.
The following video explains, with incident reports, how dangerous Delta P is. It also covers preventative measures to recognize and be prepared to deal with Delta P should the need arise.
Watch the following very informative video about Delta P and below.