Underwater Bow Thruster Removal

A Hydrex diver/technician team mobilized to Rotterdam last month to remove the bow thruster of a 300-meter container vessel. The unit needed to be overhauled. Hydrex performed the operation underwater using the company’s own workboats based at the Antwerp depot. This made it possible for the owner to keep his vessel out of drydock.

The team mobilized from the Hydrex headquarters in Antwerp after all basic preparations had been made and the needed equipment was loaded onto one of the Hydrex workboats. The Hydrex catamarans are fully equipped as dive support stations with hydraulic cranes, winches, nautical and communication equipment and a dive control room. They can be used for a wide range of operations in Belgium, the Netherlands, the United Kingdom and France, permitting even more rapid deployment from the Antwerp depot. This increases flexibility of operations and helps to keep costs down for the client.

After they arrived in Rotterdam, the divers installed flexible mobdocks on both sides of the thruster tunnel. Next they emptied all water from the tunnel. This created a dry working area around the bow thruster unit. The team could then detach the bow thruster blades one by one.

The blades were replaced by a blind flange to prevent oil leaking from the thruster and water from ingressing. Next the diver/technicians removed the flexible mobdocks again, concluding the first part of the operation.

The following step was to secure the gearbox with hoisting equipment. The team then disconnected the bow thruster unit from the engine room and lowered it onto a cradle. This cradle was designed especially for thruster operations. It can be adjusted to the size of the unit. In this manner the thruster is prevented from tipping over and Hydrex divers can remove the unit in one take.

The bow thruster was then brought onboard the Hydrex workboat, ready to be overhauled. Next the team securely sealed off the engine room by positioning a flange over the space connecting the thruster tunnel to the room. This allows the vessel to sail until the overhauled unit is reinstalled.

With the bow thruster unit on deck the team sailed back to the Hydrex headquarters. From there the unit was transported to the manufacturer to be overhauled.

Performing a job like this on a tight schedule takes a lot of planning. This can only be done successfully by staff who have familiarity with such operations and the relevant know-how and equipment. Hydrex has a technical department capable of executing all the required planning. Our diver/technicians are trained and qualified to perform the full range of required class-approved repair procedures in even the harshest conditions. Hydrex also has very well-equipped rapid response centers including customized workboats, ready to mobilize directly to the job site. This saved the owner precious time and money.