Underwater repair specialists, UMC International were recently contacted to assist with permanent insert repairs to a 95371-ton tanker at Portland Inner Anchorage.
An experienced UMC team was quickly on site to carry out an immediate underwater inspection of the damage, in conjunction with a Testbank Afloat Repair Team and a DNV Class representative.
The inspection uncovered extensive repairs with a total of seven shell-plating inserts to be carried out. A repair procedure was devised and project managed by UMC marine engineers with the underwater placement of steel cofferdams to allow defective sections of shell plate to be removed and replaced.
UMC cofferdams, including a 500kg, 3 meter x 600mm cofferdam that could efficiently cover three of the cracks were specially designed and fabricated.
Once in situ and confirmed to be a dry habitat by the UMC dive team, the internal repair crew cut away the longitudinal stiffeners and the defective sections of shell plating. Testbank welders repaired the cracks utilising a single sided weld procedure with ceramic backing strips on the outside of the hull. The new inserts were then welded in position utilising constant flux core MIG welding.
After allowing a 12-hour cool down period an NDT (non-destructive testing) inspection of the welds was carried out utilising M.P.I and UT and following a DNV inspection, all inserts were found to be free from faults.
On completion of successful NDT, divers removed the cofferdams and carried out a CCTV inspection of the external weld cap, divers then applied an underwater epoxy paint over the entire insert plate and weld cap.
UMC Engineering Director, Dave Richards said, “These type of afloat insert repair procedures allows the vessel to sail in good time and help reduce repairs at their next dry docking.
He continued, “We have project managed and completed many insert repairs from our operational hubs around the world and designed a variety of hefty cofferdams, some weighing over 10 tones’.”
