• Underwater bow thruster removal and reinstallation in Rotterdam

    Underwater bow thruster removal and reinstallation in Rotterdam

    27/09/2012

    To save time and money for the owner of a 334-meter container vessel, Hydrex removed the bow thruster of the ship and installed a new unit during the vessel’s scheduled stop in Rotterdam. By carrying out both parts of the operation underwater the ship could continue its commercial operation and did not have to go to drydock.

    The removal and reinstallation took place in July, but earlier a Hydrex diver/technician team performed a full underwater inspection of the bow thruster unit and removed the propeller blades. This was done during a previous stop in Rotterdam. On the one hand, this allowed the Hydrex technical department to prepare every step in detail to make sure that the team could carry out both the removal of the old bow thruster unit and the installation of the new unit during a single operation. On the other hand the removal of the blades would shorten the removal of the thruster unit and would allow the container vessel to keep its tight commercial schedule. During this first part of the operation the new thruster unit was also brought onboard the vessel.

    When the vessel was sailing towards Rotterdam again, a team mobilized from the headquarters in Antwerp together with all the necessary equipment.  They set up a monitoring station in preparation for the vessel’s arrival. As soon as the ship was berthed, the diver/technicians went on board and prepared the bow thruster engine room for the removal of the unit so that there would be no ingress of water once the unit was taken out.

    The team then disconnected the bow thruster from the thruster room and carefully lowered it. The divers then extracted it from the tunnel and brought it to the surface. Simultaneously the team installed a blind flange to seal off the thruster tunnel from the engine room. Once the old unit has been overhauled it will be kept as a spare thruster.

    The new bow thruster unit was put on a cradle which was designed specially for bow thruster replacement and prevents the unit from tipping. It can be adjusted to the size of the thruster and allows the Hydrex divers to bring the unit back into the thruster tunnel in one take.

    Next the diver/technicians sealed off the thruster tunnel with the Hydrex flexible mobdocks and emptied all water from it. This created a dry working environment in which they could complete the reinstallation of the bow thruster unit in drydock-like conditions. They repositioned the gearbox using chain blocks and secured it with bolts. The thruster propeller blades were then reinstalled one by one and the thruster unit was reconnected to the engine room.

    The Hydrex team worked in shifts around the clock to finish the job within the available time frame. The ship had to shift twice to continue its loading and unloading, but the flexibility of the diver/technicians made sure that this could be done without losing time.

    Performing both the removal and reinstallation on such a tight schedule takes a lot of planning. This can only be done successfully by people who have familiarity with such challenges and the relevant know-how. This is why Hydrex has a technical department capable of executing all the required planning, an in-house Research & Development department that can take care of the engineering aspect of an operation and diver/technicians who are trained and qualified to perform the full range of required class-approved repair procedures in even the harshest conditions. An effective, competent team is the only way to consistently achieve a high quality result in the short periods of time usually available to ships.

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