The result of the inspection determined that an insert of 1600mm x 600mm was needed.

The team began to prepare the insert by cutting it to the correct size and, once done, placing it in the mobdock that was going to be fixed to the external hull and used to seal off the area.

(A mobdock is a mobile mini dry-dock - Hydrex's adaptation of the cofferdam principle) The insert was too large to go through the manholes within the vessel and so had to be brought to the hull within the mobdock.

Whilst the insert preparation was being done, pad eyes were welded on the hull as these were to be used to secure the mobdock to it. By evening the actual installation work of the mobdock had begun.

The approximate size and placement of the area to be repaired had been communicated in advance so that the correct type of mobdock could be prepared and transported to Le Havre.

Unfortunately, the fact that there were significant indentations in the hull around the area where the insert was to be fitted was not known. Consequently, when the team attempted to fit the mobdocks they were unable to make it watertight and needed additional equipment and material to deal with this problem.

At this point in the operation it was midnight on a Saturday and there was nowhere in Le Havre to get the needed supplies, nor was it likely they could be found the following day. The team leader called the 24/7 Hydrex base in Antwerp and the needed materials and equipment were arranged to be transported to Le Havre immediately. Six hours later they were in Le Havre and the mobdock could be sealed to the hull so the work could continue.

Once the mobdock was fitted and all water pumped out, the exact size of the insert plate was marked out on the inside of the hull. A scaffolding had had to be constructed within the vessel to reach the section of the hull internally. In addition, the insert covered an area on either side of a web frame and so this also had to be cut away in order to get to the damaged area. Once all this had been finalised, the hull plating was burnt out making way for the new insert to be brought into position.

When this was complete the full penetration welding started from inside the hull in accordance with approved welding procedure.

Once the welding was complete, the quality of the work was checked by ultrasonic testing and found to be without any defect. The web frame was then also welded back in place.

At this point the mobdock was removed from the hull plating and the full penetration weld was ground flush. The vessel was again fully operational and left port.

MJ Information No: 19118