Hydrex has an in-house Research & Development department that can take care of the engineering aspects of an operation. In this way turnkey solutions can be offered for complex hull and other repairs that require the construction of specific equipment.

All the projects we undertake are engineered and carried out in close cooperation with the customer and any third-party suppliers. We begin with evaluating the feasibility of an underwater repair, continue through design and construction of customized equipment and go all the way through to successful execution of the repair or replacement and subsequent follow-up. We take on, organize and execute the entire job, start to finish, relieving the customer of all the hassle of coordination, planning and supervision.

Below you can read some examples of the many customized solutions our R&D department has designed for ship owners over the last 50 years.

Replacement of a complete, prefabricated hull section at anchor

In July 2011 the Tsavliris Salvage Group urgently dispatched a salvage tug in response to a call for assistance from bulk carrier Navios Sagittarius. The vessel had run aground on the Tonneberg Banke, about 23.5 miles east of Frederikshavn, Denmark.

The vessel was towed to Frederikshaven for a detailed underwater inspection, extensive bottom repairs, and reloading of cargo. The chief subcontracting company for the inspection, planning and repair work was Hydrex. The complex salvage operation lasted three months.

Without accurate measurements and data, the naval architects could not produce drawings and plans which would make this repair possible. So, the first step for the Hydrex divers was to perform a detailed inspection of the two major areas of damage on a hull that was badly deformed, pierced, torn and indented.

Using these measurements and the original drawings of the ship, the naval architects were then able to produce final drawings from which a section and a doubler plate could be fabricated and installed. As soon as fabrication of the section and the doubler plate was completed, preparation for installation began. In the case of the section, it was necessary to cut through the hull plates where the hull was distorted and broken. Divers proceeded to cut a hole in the hull about 5 x 5 meters in size. The prefabricated insert was lowered into the water and rigged into place with chain blocks. While work was going ahead with the section, another Hydrex team worked on the fabrication and installation of the 8 x 1.8 m doubler plate in the area of DBBT No. 1. A frame was fabricated and used for measurement and then the plate itself was cut, pre-shaped and attached.

Speed was of the essence for this operation as the ship was on a long-term charter and each day it was out of service was costing tens of thousands of dollars. It was the first time ever that an entire hull section had been prefabricated and inserted into a ship’s hull, cutting away the existing damaged plates, with the ship still afloat.

Underwater repairs in the U.A.E. allow ship to sail on after a 150-meter large grounding damage

Almost back-to-back with the operation described above, we sent a nine-man diver/technician team to a 300-meter bulker’s location, 21 miles off the coast of Fujairah, United Arab Emirates. The ship’s shell plating was indented over a length of 150 meters after a grounding in the Suez Canal, and a large crack 1.5 meters long appeared, making it impossible for the vessel to sail any further. We were asked to close off the crack to allow the vessel to continue its route.

The flooding had lowered the fully loaded ship from a draft of 18 meters to 22 meters. Because such a water depth means shorter diving intervals, a large diving team was immediately mobilized to the vessel to allow the team to work continuously for the 12 hours that were available each day.

To get a perfect assessment of the way the shell plating had been compressed, a special frame was made and secured over the damaged area. This allowed the diver/technician team to take exact measurements of the distorted plating. These measurements were then used to create a special cofferdam that would cover the crack and prevent it from growing further.

After the cofferdam had been positioned and secured, it was reinforced with longitudinal stiffeners and additional fortifications until it was strong enough to hold the water pressure. The tank behind the crack was then emptied, bringing the vessel back to its previous draft of 18 meters. In total the reinforcements covered an area of 18m2 and the combined length of all the welds was over 500 m.

When the operation was finished, only a few reinforcements had to be added to the inside of the hull to prepare the ship for its journey to China.

Emergency hull repair on ferry Texelstroom

When the vertical side of the ferry Texelstroom was damaged during storm Eunice in 2022, a leak in the ballast water tank prevented the ship from sailing. Because this happened at the start of a busy school vacation period, it was essential that a fast on-site solution was found to keep the downtime for the ship as short as possible.

Texelstroom sails between Den Helder on the Dutch mainland and Texel, the largest and most populated Dutch Wadden Sea island. As a UNESCO World Heritage Site, it is important that the area be protected. Texelstroom was designed with this in mind.

We were asked by TESO, the owners of the vessel, to find a way to repair the damage the ship had suffered during the storm. Because no drydock was available on such short notice, the operation needed to be performed while the vessel was afloat. Another important factor was the timeframe. Downtime needed to be kept to the absolute minimum so that Texelstroom could get back to ferrying passengers between Den Helder and Texel as soon as possible.

Our Technical Department proposed installing an open-top cofferdam over the damaged hull plating. This would allow our diver/technicians to access the affected area and perform the needed repairs in dry conditions.

On Friday morning our team arrived in the port of Texel with the cofferdam and all the needed equipment. In consultancy with the superintendent of the ferry and the surveyor from the classification society it was agreed to install an insert repair measuring 1500mm x 700mm.

The team then installed the open-top cofferdam over the damage and created a dry environment in which to work. They cut away the old plating and installed the new insert. Our men secured the insert with a certified weld both from inside the vessel and inside the cofferdam.

The teams worked in shifts around the clock. This allowed us to complete the actual repair in just two days.

TESO’s spare ferry Dokter Wagemaker had been bringing passengers to the beautiful Island of Texel during the Texelstroom’s sick leave, but the ship was all better now and ready to sail again at full strength.

Extensive doubler plate repair in Ivory Coast allows bulker to sail after collision

In 2013, a 190-meter bulker suffered severe collision damage in Lagos, Nigeria. A large hole in the hull plating prevented the ship from sailing at full speed. The classification society also demanded that the vessel go to drydock immediately unless an on-site solution was found. Hydrex therefore sent a diver/technician team to the vessel’s location to carry out an emergency doubler plate repair at anchorage. This would give the owner the opportunity to take his ship to drydock when he wanted and where he wanted.

Because of the rainy season in Nigeria, underwater visibility was almost non-existent, and the current was too strong to carry out repairs at anchorage. Abidjan was the closest location suitable for this type of operation.

At this new location the team cut away part of the deformed plating. This created an even surface to position the doubler plate. Next the team made crack arrests to make sure that the cracks would not spread any further.

The bottom part of the doubler plate was then lowered from the deck and positioned over the lower half of the opening. This part of the plate was 4.5 meters wide and 2 meters high. The diver/technicians then welded the plate onto the hull. Horizontal stiffeners were then installed on the plate to give it extra strength. This could not be done in advance because it would have prevented the team from adjusting the plate to the exact shape of the damaged hull.

The same procedure was repeated for the top part of the doubler plate. This part of the plate was trapezium-shaped with a width of 4.5 meters and a height of 2.5 meters. Both parts of the plate were then welded together to finalize the repair.

45-ton cofferdam repair after a severe grounding

A fully laden bulk carrier suffered heavy damages from a grounding in Suez in 2022. The owners’ and management’s first thought was to call Hydrex. In this case the ship was carrying a valuable cargo and every day she was out of action represented a huge loss to the owners.

Based on the initial inspection and rough measurements, a plan was proposed to carry out precise measurements of the hull where the large damage occurred so that a cofferdam could be designed which would then be installed to make the hull watertight so that the water ballast tanks could be pumped out.

As soon as the fabrication was completed by a local workshop, we flew back to Suez. After some needed modification, the massive, 45-ton cofferdam was lowered into position by crane and secured against the hull.

The pressure of the water was, however, too much for the structurally weak hull which started to cave in when the ballast tank began to be pumped out. It became clear that the ship had suffered too much internal damage to permit the water ballast tanks to be fully pumped out. This was not something that could have been predicted or remedied with the ship afloat.

In order to reinforce the bulkhead between the water ballast tanks, a new plan was proposed to build cement boxes and pour concrete to provide enough strength for these bulkheads. But WBT 2 port could not be emptied. Part of the plan, therefore, was to lighter the ship as necessary until the class-required draft could be achieved.

With the cement boxes in place, the cofferdam was fully secured, and successful sea trials were conducted. The cofferdam remained firmly in place until it could be removed when the ship was in drydock and permanent hull repairs could be carried out.

Summary

Our goal is to offer customers the most efficient solution, whether the required services involve the inspection of a vessel’s condition along with any required maintenance work, or highly technical major repairs and replacements of a ship’s external underwater equipment and machinery. In all cases we strive to reduce cost and off-hire time for customers while maintaining the highest quality standards of repair and maintenance.