When the cruise ship MV Discovery started taking on water in the English Channel, the ship's engineers identified the cause as a corrosion hole approximately Ø100mm at the point where the margin plate met the hull plating in the Port Shaft Tunnel. Class (Lloyds) were notified of the damage and insisted that a permanent repair was carried out on the ships structure prior to further vessel operation.
The availability of dry docks was an issue and would prevent the subsequent cruise schedule being met. In addition, dry docking the vessel would mean that the crew would not be able to complete mandatory safety afloat drills for the MCA. Thus an alternative approach was required.
UMC were approached to investigate the feasibility of an in-water repair. The initial Lloyds survey was undertaken in Falmouth where the hole was blanked from the outside to allow thickness readings of the surrounding hull plate. This concluded that a full insert repair was required.
The size, location and geometry of the ships hull in the vicinity of the hole allowed a stock cofferdam to be deployed and was fitted by a team of UMC divers. Once de-watered, this allowed steelworkers to cut out the affected area and carry out the class approved permanent insert repair. Utilising ceramic backing plates and single-sided welding, all work could be carried out from inside the vessel. On completion, NDT was carried and with results to the satisfaction of class.
The whole operation was overseen by UMC and carried out over a 3 day duration, which provided a much faster and cheaper option to the owner than a dry docking period.