• Permanent afloat repairs with unique rudder mobdock

    Permanent afloat repairs with unique rudder mobdock

    28/10/2016

    We perform repairs at anchorage on any type of rudder or while the vessel is berthed without interrupting cargo operations. In most cases these repairs are permanent and do not require follow up.

    Permanent in-water rudder repairs were previously not possible and ships had to drydock in cases where a major defect was found. We have however designed equipment that allow us to perform permanent rudder repairs on-site. The equipment can be mobilized to any port in the world at moment’s notice. This enables us to offer this service very swiftly on a worldwide basis.

    Major defects on rudders very often cause unscheduled drydocking of ships. The technique designed by our R&D department allows engineers, welders and inspectors to perform their tasks in a dry environment with the vessel still afloat.  With the use of our flexible mobdock technique class approved permanent repairs are now possible on-site. Steel repairs and replacements can be performed and other technical defects can be solved without the loss of time and money associated with drydocking.

    Balanced rudder repair in Antwerp

    Hydrex was contacted by the owner of a 200-meter vehicle carrier because the rudder of his vessel was not working properly. A diver/technician team therefore mobilized from our headquarters with one of the workboats loaded with all the needed equipment.

    After arriving at the ship’s location in Antwerp, the team first performed a detailed underwater inspection. This revealed several irregularities on the rudder seals.

    Our universal rudder repair mobdock allowed the rudder specialist that was present to perform further inspections in drydock-like conditions. He could then make a detailed assessment of the situation of the rudder and observed several reasons for the malfunctioning.

    Following the inspection we proposed a repair plan which was accepted by OEM and the owner. The team then carried out several repairs to remedy the rudder problems. First the existing rudder seal was tightened. Next the two wrong-sized rings were replaced with correct ones and both the upper and lower casing of the rudder seal assembly were reinstalled. The team pumped grease into the system and secured all nuts and bolts. The vessel could then continue its schedule with a fully functioning rudder.

    Rudder repair case studies

    The following case studies give an account of some of the other more important recent underwater rudder repairs performed by Hydrex. They showcase the wide variety of repair solutions we can offer to shipowners.

    Emergency flap rudder repair in Greenland

    We received an enquiry for an emergency rudder repair on a 67-meter fishing vessel. The ship was operating in the region of Sisimiut, Greenland when a defect occurred on her flap rudder, making it difficult to navigate safely.

    A preliminary inspection by a local diving company revealed that one of the hinges of the rudder flap had come loose. To keep on sailing without a repair posed a great risk as there was a real chance that the damage would have deteriorated. Securing the rudder flap was the only possible underwater solution.

    This inspection, combined with drawings received from the OEM, gave our technical department all the information they needed to make the necessary preparations. Steel plates that would be required for the repair were prepared at a local workshop while our team mobilized.

    A team of our diver/technicians arrived at the remote location of the vessel just over a day after the green light for the operation had been given. The polar weather conditions of Greenland proved to be no problem for our divers, as they are experienced in delivering the same high quality in difficult circumstances.

    A secondary underwater inspection was performed by our divers to get the exact measurements for the girders. Next the plates were cut on-site by our team to the exact size. The rudder and its flap were then put in the neutral position. Three girders were placed on each side of the rudder, securing the flap to the rudder. The plates were welded underwater by our divers. A steering test was successfully performed, concluding the repair.



    By immediately mobilizing a team to Sisimiut to carry out a temporary repair, we allowed the owner to keep his vessel operating instead of having to plan an unexpected docking. Because of the remote location of the vessel there was no suitable drydock close by. As a result this would have meant an extended off-hire time. With a well calibrated rudder the ship could keep on sailing until the next scheduled drydock visit.

    Underwater rudder plate repair in Haifa

    When a 260-meter container vessel suffered a crack on its rudder, a Hydrex team traveled to  Haifa, Israel to carry out a repair.

    The divers started the operation with a detailed underwater inspection of the affected area. This was done under the supervision of a representative of the classification society. With the measurements taken during this inspection, a complete assessment of the damage could be made. This allowed us to create the best possible repair plan for the problem.

    A 690-mm crack was found, partially covering the weld seam of the portside rudder cover plate. The crack was curved at the top and the bottom. Crack arrests had already been made at both ends to prevent it from spreading further. A more thorough solution was now needed to fix the problem.

    In consultation with the class surveyor a repair plain was devised. First the Hydrex diver/technicians ground out the crack in a v-shape. They also ground the surrounding area. Then a root weld was put in the crack.  Next the team filled the crack with welding beads. The repair was finalized with a steel reinforcement bracket that was installed over the middle of the area.

    A successful pressure test was performed to make sure that the dry rudder compartment behind the crack was not compromised. The surveyor then gave his approval for the repair.

    Underwater rudder repair in Rotterdam

    A Hydrex diving team mobilized to a 170-meter container vessel with one of our workboats. The team installed a doubler plate over the cavitated area of the rudder during the ship’s scheduled maintenance stop in Rotterdam.

    An earlier inspection carried out in Algeciras had revealed the damage to the rudder. A condition of class was imposed on the vessel and a custom solution was needed. We proposed a repair plan to the class that would allow the vessel to keep sailing until the next scheduled docking.

    Deployment to the vessel was done using a Hydrex workboat loaded with all the needed equipment. After our team arrived on-site, they performed an underwater inspection of the leading edge of the rudder, where the damage was situated. The divers then started preparing the affected area for the installation of the doubler plate. The plate had been prepared in advance. This was done with the information of the preliminary inspection in Algeciras combined with the drawings of the rudder, provided by the owner.

    When the rudder had been prepared our certified diver/welders fitted the plate and secured it. The team then installed anodes on both sides of the rudder for further protection. This concluded the repair.



    During the operation a representative of the classification society was present. He gave his approval for the repair. The owner can now sail his ship until the next scheduled drydocking without having to worry about further unscheduled delays or repairs to its rudder.

    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. We have 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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