A one year old, fully loaded bulk ore carrier was invloved in a collision off the coast of West Africa resulting in considerable damage and a large hole just aft of amidships extending below the waterline. The hole measured 7.1m high and 4.9m along the ship and caused flooding to the carge space which resulted in massive reduction in freeboard.
It was stipulated through class that the vessel had to be sealed and pumped dry for internal inspection and repairs, before attempting a voyage to the nearest dry dock 450 miles away. The challenge was the extent of damage combined with operational constraints in Conakri.
A team of welder divers were sent to survey the vessel and seal the hole. On arrival, the hole was fully submerged due to progressive water ingress. The main problem was the lack of local materials. Some 10mm plate was available but this required extensive stiffening to be used at 9 metres below the waterline. On analysis of the hatch cover drawings it was decided to cover the main part of the hole with one section of the sliding hatch, measuring 15 x 5m. Steel plates of 6.25 x 2.5m and 3.75 x 2.5m were used to cover the hole closer to the waterline. Margin plates were cut and welded in place to fill the gaps between the hatch cover and adjacent hull. Additional stiffeners were underwater welded to the steel plates to reinforce between the plates and the hull. Finally the entire perimeter of the patch was sealed to the hull by underwater welding.
This enabled the cargo hold to be pumped dry and inspected internally. Internal stiffeners and supports were welded in place as specified by class, to further reinforce the patch. Concrete was poured to the bottom of the cofferdam to provide further support. The whole operation was overseen by UMC and design support in the UK.