A roro vessel suffered corrosion damage to the aft starboard side shell plating. We mobilized a team from our office in Tampa Bay to the vessel’s location in Palm Beach to perform a class approved permanent underwater insert repair. This allowed the owner to keep his ship on schedule.

The team started the operation with a detailed inspection of both the onboard as well as the water side of the affected plating of the roro vessel.

Next the divers installed a cofferdam over the waterside of the affected area. Because the damage was situated in the turn of bilge it was essential that the cofferdam was modified to fit perfectly over the rounded shape of the hull.

The frame covering the damage was then removed. This allowed the team to cut away the damage and the surrounding area. Next they positioned a new insert plate, measuring 500 x 660 mm. The insert was then welded following the Hydrex class-approved procedure for insert plates, using a full penetration weld. Next to the insert a strip of less severely corroded shell plating was repaired with clad welding.

An independent inspector carried out ultrasonic testing and the repair was approved by the classification surveyor who was present during the operation. The diver/welders then refitted the frame and removed the cofferdam, concluding the repair.

Conclusion
The divers also carried out a full inspection of the underwater hull of the roro vessel as well as cleaning its two propellers. By combining several jobs, the entire operation could be carried out economically and within a very short time frame. Only one mobilization needed to be planned.

Repairs like this can be carried out above or below water, according to the circumstances, with external cofferdams. Normal commercial activities can therefore continue without disruption. These operations follow the Hydrex procedure for welding cracks and inserts in the vessel’s shell plating and they are approved by the major classification societies.