“In the early 20th century, it would have been considered suicide for a diver to shoot an electric arc into the water. Though professional diving was already an established industry and had been for hundreds of years, underwater welding was not. That all changed when Konstantin Khrenov, a Soviet engineer, invented a method to join and cut metals underwater.

“Khrenov wanted to find a way to weld underwater for quicker vessel repairs. WWI had ended, but WWII was beginning to brew and the USSR was mobilizing its fleets. As Khrenov discovered, one of the largest hurdles to successful wet welds lie in the sporadic outflow of gas bubbles from the point of contact with the arc and metal. This reaction caused major porosity in the welds, and the bubbles burst out, untamed. With the help of others, Khrenov devised a waterproof coating for the electrodes, and a stable power source.

“In 1932 after successful experimentation in the labs, Khrenov traveled with engineers to the Black Sea for further successful testing. Underwater welding was born.”[1]

However, it was not until the 1970s that the first underwater wet welding procedure was qualified to American Welding Society (AWS) standards by White Grubbs and Dale Anders of Chicago Bridge & Iron (CB&I) and the commercial development of underwater electrodes began.

Hydrex has been at the forefront of wet welding for the last 50 years. In this period, we have regularly introduced new welding techniques. We have also developed new equipment that makes it much easier to monitor and test the weld seams. This has been done by our in-house R&D department who cooperate closely with our diver/technician teams. Together they help us undertake the research required to keep evolving the available welding techniques.

Training of our divers consists of both theoretical classes in the course room and practical drills on our premises. There they have access to a wide range of underwater tools and a variety of other equipment, including a dry welding training area and three dive tanks in which to practice underwater welding.

We can carry out classification certified grade A wet welding. To guarantee the required high standard of these underwater welds, NDT tests are performed by ABS surveyors before the certificates are awarded.

New divers also get the opportunity to assist veteran team members during operations. The training enables them to become experienced divers/technicians and take advantage of the technical know-how and practical knowledge we have accumulated over the last 50 years.

Below is a summary of just a few of the many underwater welding repairs that illustrate the vast welding experience we have built since 1974.

Hull repair on drill ship

The transit flap of a 225-meter drill ship came loose and started swinging dangerously. This caused damage in the aft bulkhead and a leak in the ballast tank situated behind the moonpool hull. A fast solution was needed to prevent further damage.  The vessel was in Dakar.

We mobilized a team of diver/technicians. After an inspection of the damage, they disconnected the transit flap. It was then brought to shore, cut in three pieces and taken away. The divers also took all the measurements needed to design a repair plan for the second phase. Because of the unstable condition of the flap, it was essential to keep to the highest safety standards, especially during this first part of the operation.

The second part of the operation consisted of the installation of six doubler plates over the damaged areas in the aft bulkhead. Constructed with the exact measurements taken during a detailed inspection, they were positioned and secured underwater by our certified diver/welders. All water was then emptied from the damaged ballast tank. The crew performed an inspection of the tank and confirmed that the compromised hull was once again fully sealed.

Thanks to the installation of the doubler plates, the ship could safely start its contract. A permanent solution could be planned at a more opportune time.