• Underwater thruster repairs adapted to your vessel's schedule

    Underwater thruster repairs adapted to your vessel's schedule

    28/02/2017

    Hydrex diver/technicians can perform a wide range of repair or maintenance work on all types of thrusters. An entire unit can be overhauled, propeller blades and seals can be replaced or repair work on another specific part of a thruster can be performed on-site or inside the tunnel. These repairs are performed in cooperation with OEMs.  They can be carried out while the vessel stays afloat with minimum impact on its schedule.

    Tunnel thruster operations specifically are carried out using our flexible mobdocks that close off the thruster tunnel on both sides. This allows divers to work in a dry environment around the unit. The lightweight mobdocks can quickly be transported to any location around the world. All operations can be carried out in port during cargo operations or at anchorage. An animation of the procedure used can be viewed on the special thruster repair page of our website or can be requested by contacting one of our offices.

    The size of the thruster does not matter. Hydrex flexible mobdocks can be easily adapted  to the circumstance. They can be used for a wide range of repair or maintenance work on all types and sizes of thrusters and vessels.

    Despite the scope of some these operations, bow thruster removals can be performed very fast. The removal of the unit can be done in the wet, because it has to be overhauled. We only need to remove the blades and close the unit off with flanges. The reinstallation needs to be done in the dry because the blades need to  be reinstalled without water ingress.

    In most cases a thruster overhaul is planned in during a scheduled drydocking. This usually means that the unit is removed in drydock. The ships then has to wait for the overhauled thruster to return and be reinstalled before the vessel can leave drydock. This results in a longer drydock time and consequent cost. Hydrex can however remove the unit while the ship is still afloat so it can already be brought to the manufacturer for the overhaul. When the vessel enters drydock the overhauled unit is ready for reinstallation without any delay.

    The reverse procedure is also possible. If the thruster is removed in drydock, Hydrex can reinstall it underwater in dry conditions at later date. In this way the ship can already leave drydock while the unit is still with the manufacturer.

    Our goals is to offer you the most efficient solution while maintaining the highest safety and quality standards. This article gives an overview of some of the more important recent thruster repairs carried out by Hydrex.

    Simultaneous underwater repairs on two offshore vessels in Mexico

    Last year a team of experienced Hydrex diver/technicians performed underwater thruster operations on two vessels simultaneously in Coatzacoalcos, Mexico. Repairs were carried out on both azimuth thrusters of an FPSO while the thruster seals of a heavy load carrier were replaced.
     
    Both vessels are managed by the same company. They were suffering from leakage problems on their propulsion system. We received these inquiries and were able to combine both repairs in one operation. This gave our costumer the advantage of only one mobilization for both vessels and kept the cost within budget.
     
    The stern thruster tunnel of the heavy load carrier was sealed off with our flexible mobdocks. All water was then emptied from the tunnel, creating a dry workspace around the thruster unit. A full inspection of the unit revealed that all blade and shaft seals were leaking. Our diver/technicians first replaced the four blade seals. The three shaft seals were then replaced in cooperation with the representative of the OEM.
     
    The other vessel was an FPSO which had suffered a problem in the oil distribution box of one azimuth thruster. A special cofferdam was designed by the Hydrex R&D department to create a dry environment around this part of the thruster. This enabled our team to perform a complete repair without removing the thruster. The other azimuth thruster had more serious problems and a complete removal was required. As the thruster was not designed to be removed underwater, we created a custom procedure for this.

    Flexibility is an important element of every job we carry out, but in this case it was crucial that both repairs were adjusted to each other. Because we were able to fulfill the needs of our customer he could keep the vessels out of drydock and on contract.



    Fast response keeps vessel on project in Australia
    We removed the bow thruster of a large offshore supply vessel and reinstalled the unit after it was overhauled.  By carrying out both parts of the operation underwater while the vessel was at anchorage in Dampier,  Australia, the ship did not have to go to drydock and could stay on the project.

    Despite the remote location of the vessel, our technical department was able to make all logistic arrangements and organize a mobilization of the equipment swiftly. Recently we have carried out several operations in Australia, all of which were done with a limited window of opportunity available.
     
    After our divers removed the bow thruster unit it was brought to a local workshop where it was overhauled by a technician team of the OEM. The Hydrex team remained on stand-by so that they could immediately start the dry reinstallation when the bow thruster arrived back on location.

    During the entire operation there was a close cooperation with the OEM so that the different parts of the repair were perfectly coordinated. This allowed us to offer the best possible solution to our customer within the shortest possible time-frame.

    Hydrex enables OEM to access bow thruster out of drydock
    When a 162-meter pipe laying vessel suffered an oil leak, going to drydock for bow thruster repairs seemed the only option. The owner contacted us to see if we could develop an underwater solution that would allow the OEM specialists to access the thruster tunnel while the vessel was still afloat. This would avoid off-hire for the vessel.
     
    One of our technicians met up in Mobile, Alabama, with the owner and representatives of the OEM to discuss the repair plan devised by the Hydrex technical department. This proposal included the installation of two open top cofferdams to close off the thruster tunnel.
     
    The operation required Hydrex to think and handle fast to allow the owner to keep his ship on project. The schedule of the pipe laying vessel offered only a window of two weeks to develop an underwater solution and two further weeks to carry out the operation, including the building of both cofferdams.

    Underwater bow thruster removal adapted to the ship’s schedule
    A month after a Hydrex diver/technician team removed a bow thruster unit which needed to be overhauled from a 360-meter container vessel, the same procedure was repeated on the vessel’s sister ship. As with the earlier operation, the team first prepared the thruster tunnel during the ship’s stop in Le Havre, France before carrying out the removal itself in Rotterdam.

    The available window in Rotterdam was very short for both vessels. The time required to remove the thruster unit therefore needed to be brought back to the absolute minimum. Splitting the job into two steps allowed our divers to perform these operations underwater and in a very short time frame without interrupting the vessels’ schedule. Both operations were carried out using one of the Hydrex workboats which are fully equipped as dive support stations and can be used for a wide range of operations. They increase flexibility of operation, which is essential during operations like these.

    Conclusion
    Performing jobs like these 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. 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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