• Swift underwater thruster repairs and replacements keep ships out of drydock

    Swift underwater thruster repairs and replacements keep ships out of drydock

    25/10/2012

    In the last few years Hydrex divers have carried out thruster operations on numerous occasions around the world. This article gives a summary of some of the more important ones.

    Underwater bow thruster removal and reinstallation in one take Antwerp
    In July, Hydrex performed the removal of a bow thruster that needed to be overhauled, and reinstalled a spare unit in one take. Both parts of the operation were carried out during a 200-meter container vessel’s stop in Antwerp.

    A diver/technician team carried out a preliminary inspection and took the necessary measurements prior to the ship’s journey to Antwerp, while the ship was berthed in Algeciras. This allowed the Hydrex technical department to prepare every step of the operation 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, in the fastest possible time and without any loss of quality.

    Together with all the necessary equipment, the team mobilized from the headquarters in Antwerp to the vessel’s location. One by one the diver/technicians detached the blades and replaced them with blind flanges to prevent oil from leaking from the thruster. In the meantime, initial preparations were made in 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.

    Next the team cut the support brackets connecting the gearbox to the thruster tunnel and secured the unit with chains. It could then be fully disconnected from the thruster room and was carefully lowered, extracted from the tunnel and brought 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 used as spare thruster for future operations.

    Next the new bow thruster unit was put on a cradle which was designed specially for bow thruster operations and which prevents the unit from tipping. As it can be adjusted to the size of the thruster, it allowed the Hydrex divers to bring the unit back into the thruster tunnel in one take.

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

    Hydrex took on, organized and executed the entire job, start to finish, relieving the customer of all the hassle of coordination, planning and supervision. This was done in close cooperation with the customer and third party suppliers.

    To keep the delay for the customer to the absolute minimum, diver/technicians worked in shifts around the clock. By performing both the removal and reinstallation of the bow thruster unit underwater the vessel did not have to go into drydock, saving the owner valuable time and money.

    Underwater bow thruster removal and reinstallation in Rotterdam
    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.

    Replacement of azimuth thruster on crane barge in Gabon
    A Hydrex diver/technician team mobilized to an offshore crane barge stationed at its service base in Gabon to replace one of the vessel’s swing-up azimuth thrusters with the spare.

    The operation had to be carried out in a very short timeframe because the crane barge was scheduled to leave for an operation in Nigeria. All repairs and other servicing needed to be performed before the start of this operation. For this reason going to drydock was not an option as the nearest suitable location was South Africa and this would have taken the repairs far beyond the available timeframe.

    Hydrex had carried out a similar operation on this vessel on two occasions. Four years ago when the first azimuth thruster was replaced, a large mobdock (measuring 9 x 6 x 2 meters and weighing over 25 tons by itself) was constructed under Hydrex supervision in Belgium and transported to Gabon. There it was stored after the repair. It was to be used at short notice whenever future repairs were required on thrusters. This allowed for a very fast mobilization and thruster replacement on the next two occasions.

    The operation was concluded well before the start of the barge’s next operation and presented a major saving in time and money for the owner as he did not have to take the offshore unit off hire to go to drydock.

    Underwater bow thruster replacements on several container vessels in Singapore
    When a 300-meter container vessel lost the blades of its bow thruster, Hydrex was asked to remove the damaged thruster and replace it with a spare one. The operation was carried out while the vessel was at anchor in Singapore.

    Because of the tight schedule of the ship, the entire operation was planned and launched as rapidly as possible. Just days after the order was confirmed, the equipment and eight Hydrex diver/technicians arrived in Singapore where the team was completed with an additional work force supplied by our local support.

    The old bow thruster unit was removed from the tunnel and brought onto a work barge. From there it was transported to the workshop to be thoroughly examined to determine what had gone wrong. In the meantime the spare thruster had been prepared and was subsequently brought inside the thruster tunnel and secured. The Hydrex team then installed the propeller blades.

    During this operation the diver/technician teams worked in shifts to make sure that the repair would be finished before the vessel had to depart and this despite the unavoidable loss of time that poor weather conditions brought about. The vessel could once again use its thruster to maneuver inside ports without depending on external assistance.

    Also in Singapore, a Hydrex diver/technician team reinstalled the overhauled bow thruster of a 280-meter container vessel underwater with the use of the Hydrex flexible mobdock four months after they had removed the unit.

    The superintendent of the ship was very satisfied with the first part of the operation. He said that “...the job was completed well within the timeframe of forty hours thanks to good team work of the Hydrex divers, the ship staff and the floating crane operator.” For this reason the customer asked Hydrex to take care of the reinstallation as well.

    Bow thruster removal and reinstallation in several stages across Europe
    Closer to home Hydrex carried out the removal, transportation and reinstallation of a bow thruster unit in stages in several locations to allow the vessel to keep to its sailing schedule. A 334-meter container vessel had to use the services of a tug boat for port maneuvering due to a malfunctioning thruster unit, and its owners commissioned Hydrex to take care of the entire overhaul.

    After the bow thruster unit had been removed it was transported to the Hydrex fast response center and sent on to Norway for repairs. As soon as the overhauled gearbox returned to the Hydrex headquarters it was transported to the container vessel’s next port of call for reinstallation.

    The vessel can now once again maneuver inside ports again without the need of a tugboat. Hydrex’s flexibility allowed the company’s technical department to adapt the different parts of the repair to the sailing schedule. The operation was carried out in Rotterdam, Southampton, Le Havre, Dunkirk, Hamburg and finally Rotterdam and Southampton again. Despite these multiple locations, the delay for the customer was reduced to the absolute minimum. The removal and reinstallation of the bow thruster unit underwater made it unnecessary for the vessel to go into drydock.

    Removal and reinstallation of azimuth thruster in Spain
    Hydrex mobilized equipment and a diver/technician team to perform a class approved operation on the heavy-lift, semi-sub crane vessel Saipem 7000. The inspection and the underwater removal and reinstallation of one of its 60-ton azimuth thrusters were performed in Cartagena, Spain.

    By taking advantage of one of our workboats stationed at the Algeciras office, all necessary equipment was mobilized to Cartagena where the semi-sub vessel was given a full maintenance service as part of the preparations for an operation in the Gulf of Mexico.

    Hydrex had performed maintenance and repair work for this customer before. Familiar with our procedures, he asked us to send an experienced and fully certified diver/technician team to carry out a detailed and high quality underwater inspection and azimuth thruster removal. According to Mr. Maarten Heitling, the customer’s Manager Lifting Fleet, “...the work went very well. The team and equipment were readily available for the task and the operation was carried out in a safe, professional and time-efficient manner, which is not less than what we have grown to expect from Hydrex.”

     

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