A floating dock was operated to launch a new building but, once the vessel was launched, during the refloating procedures, the ballast pump no. 7 was lost and the suction valve of the ballast pump no. 6 blocked in close position, and the dock remained submerged with a draft of 9,5 meters.
The tanks, that could not be emptied, were located 4 in aft area starboard side and 4 in middle area port side. It was tried, anyway, to refloat the dock by means of filling and emptying the remaining 24 tanks, but the dock was not able to be refloated. On the contrary, after the above mentioned refloating attempt, the dock started to sink due to water ingresses. Salvage team was appointed and, after more than 1 month, having temporary patched the water ingresses to restore the watertightness, the dock was successfully refloated.
Relevant repairs lasted about 6 months and the total cost including the salvage team was about USD 12,000,000.
As far as the cause of the accident is concerned, a rope was found iwo ballast pump no. 7 which, allegedly, caused the block of the shaft. the rope passed through the sea chest protection grating getting entangled the pump impeller. Indeed the meshes of the protection grating allow the rope to pass through. Moreover, during the attempts carried out by the drydock personnel to refloat the dock after losing 2 pumps, structural damage excessive bending moment and twist of the dock. At the time of the casualty, with 2 personnel tried to refloat the dock emptying and filling the remaining 24 ballast tanks distribution creating listing and trimming of the dock and, consequentially, overstressing The bending moment and twist of the dock caused some structural damage and relevant ingress. Consequentially, the dock completely sank, and the electrical switchboard, the motor of the pumps and all electric and auxiliary equipment were floated.
