In June a Hydrex team carried out temporary hull repairs offshore on a 67-meter shallow-water barge during its stay in Norderney and Delfzijl. Challenging weather and sea conditions required the team to adapt the original repair plan and find an alternative solution that could be carried out safely.

The damaged areas were located in void tank 4 and void tank 6. The initial plan called for three steel doubler plates to be installed externally over the affected areas. Rough sea conditions, however, made it impossible to safely bring the diving equipment on board.

Rather than wait for conditions to improve, our technical team revised the repair method. It was decided to carry out the work internally and install three reinforced steel cofferdams over the damaged areas.

Internal repair in void tank 4

The vessel’s crew had already installed a concrete box over the damaged area. Our technicians used this as the basis for the temporary repair and constructed a steel cofferdam on the inside of the tank, directly over the concrete box.

The cofferdam, measuring 1550 x 1915 mm, was fabricated from 8 mm steel plating. Reinforcing steel frames were welded to its outside to provide additional structural strength. All mouseholes were closed with small steel plates to make the repair completely watertight.

Once the welding had been completed, all welds were examined and approved by an independent third-party inspector using Magnetic Particle Inspection (MPI).

Two cofferdams installed in void tank 6

A similar solution was used for the two damaged areas in void tank 6. Prior to our team’s arrival, the vessel’s crew had installed two concrete boxes over these areas.

Our technicians fabricated two separate steel cofferdams around the existing concrete boxes. As with the repair in void tank 4, both cofferdams were constructed using 8 mm steel plating.

The cofferdams measured 1000 x 1000 mm and 1000 x 980 mm respectively. Additional steel stiffening frames were welded onto the cofferdams to increase their strength and rigidity.

After the welding work was finished, the welds on both cofferdams were subjected to MPI and approved by an independent third-party inspector.

Adapting to the circumstances

Flexibility is essential during repair operations, especially when weather conditions make the original approach impossible to carry out safely.

For the barge, the initial plan for an external repair had to be changed because of the severe sea conditions. By switching to internally installed steel cofferdams, our team was able to provide a suitable temporary solution as a viable workaround to the planned underwater operation.

All three cofferdams were reinforced to provide a strong, watertight repair and the completed welds successfully passed independent inspection.