Hydrex Underwater Technology Repairs Tank without Delaying Vessel

Hydrex recently carried out a repair to a crack in the port side grey water tank of a 145m chemical tanker. The damage was permanently repaired by Hydrex technicians, using an insert, during the vessel’s routine port call in Amsterdam.

The Hydrex team of diver/technicians began by carrying out a comprehensive inspection of the damaged area, working both underwater and onboard. The crack was found to be 480mm long, and had split in two at the port side end. The proposed repair was discussed with the vessel’s superintendent and the attending class surveyor, the decision being to install an insert, 700mm long and 300mm wide.

Crack in grey water tank seen from the outside

The engineers took measurements of the rounded hull shape using a special frame. This enabled a steel mobdock to be fabricated that would precisely fit the hull profile. The mobdock and insert plate were both rapidly made from stock materials at the fast response centre of the Hydrex headquarters in Antwerp, and transported to Amsterdam without delay.

The Hydrex team on site installed the mobdock and cut away the metal surrounding the crack, including part of the frame above the crack. The diver/technicians then positioned and fixed the new insert plate, using the Hydrex class-approved full-penetration welding procedure.

...and removal of the damaged area

After the newly-fitted insert plate had been closely inspected and approved by an independent NDT (non-destructive testing) inspector and the class surveyor, the Hydrex team reinstated the frame over the affected area.

The permanent nature of the repair carried out by Hydrex, namely removing the cracked section and installing a new welded insert, means that this area of the ship will not require any further attention during the next drydocking. The repair was carried out during the scheduled port call, well within the stipulated time frame, meaning the ship could sail with no delay.