Last month Belgian-based underwater repair firm, Hydrex sent a team to Måløy, Norway to carry out a cofferdam installation on a 140 m expedition ship.
The vessel, believed to be Hurtigruten’s ‘Fridtjof Nansen’, had suffered a large crack, as well as a smaller one in its shell plating and was not allowed to sail, following a grounding.
A fast, on-site, temporary repair was needed to allow the ship permission to sail to a drydock.
After the job had been confirmed, Hydrex immediately mobilised diver/technicians to the vessel’s location together with all the equipment needed.
Temporary repairs had been performed by another company on both cracks to stop the leaks, but these were unfortunately not strong enough. As a result, the class society did not allow the ship to sail to a drydock for permanent repairs.
Hydrex team removed the patch covering the large crack and inspected the damage, which revealed that the crack had a length of 2,000 mm and a width of 1,400 mm. Based on the inspection, the company chose to install a cofferdam covering the affected area.
This solution was gladly accepted by the expedition ship’s operator, Hydrex claimed.
As the crack was situated at the turn of the bilge, it was important that the cofferdam was constructed to the exact shape of the hull. This proved to be no problem for the team as Hydrex has almost 50 years experience with similar operations and has developed a method of attaining the dimensions needed.
A cofferdam, measuring 2,400 mm by 2,000 mm, was fabricated on-site by the certified diver/welders. It was then lowered into the water and positioned over the damage. Next, the team secured it with screw dogs and additional fortifications. It could then be emptied of water.
The other crack was much smaller with a height of 100 mm. The divers covered it with a doubler plate, which was welded into position.
Around the crack, the area had also been deformed and the bilge keel had been severely bent. Fortunately, no immediate repairs to these damages were needed as they did not weaken the hull’s integrity.
Repairs would later be handled in drydock together with the permanent repair of both cracks.
The operation was approved by the class society and the ship was allowed to sail to the drydock.