• Underwater propeller blade cropping in Yeosu restores efficiency

    Underwater propeller blade cropping in Yeosu restores efficiency

    30/04/2015

    Last month a diver/technician team performed a successful propeller blade cropping operation on a 190-meter bulker under difficult weather circumstances while the vessel was at anchorage in Yeosu, South-Korea. An underwater inspection was done by our local support base. This revealed that all five blades were bent severely, with two of the blades bent 90° or more. The blades had also suffered cracks and dents along the trailing edges. Cropping was the only option.

    With the five blades of the bulk carrier’s propeller severely bent, the motor was overloading. A fast on-site solution was needed to restore the propeller’s balance with a minimal loss of efficiency. A Hydrex team was therefore rapidly mobilized to the ship’s location in South-Korea on the same day the results of the underwater inspection came in. With these results our technical department devised a repair plan to restore the efficiency of the damaged blades as well as the propeller’s balance. This kind of repair is carried out with the propeller blade cutting equipment developed by the Hydrex research department. The equipment is lightweight and could easily be mobilized together with the divers.

    At the time of the repair there was a very high current. This meant that there was only a very small window available each day for our divers to safely perform the operation. Hydrex diver/technicians are trained to adapt to difficult circumstances and still carry out underwater repairs in the shortest possible time frame. They do this while keeping to the highest safety and quality standards. Their expertise and experience allowed them to easily divide the operation in parts so that they could crop the blades spread out over a number of days.

    After the team arrived at the vessel’s location, they started the underwater operation with a detailed survey of the affected propeller blades. The information acquired during the inspection was then used to calculate and determine the correct measurements needed to crop the propeller blades.

    Next the divers cropped the blades and ground out the cracks in the blade edges. When the cropping was complete, the blades were polished to make sure that any remaining loss of efficiency would be minimal.

    During the cropping a class surveyor was present. After a final inspection was performed, he gave his approval for the operation.

    Conclusion
    Damaged propeller blades will have a performance below average.  The engine will have a higher work load. This results in increased fuel consumption and added stress. If straightening is not an option, the affected area on the blade will be cropped. By doing this the greatest possible efficiency is achieved for the vessel. This type of repairs can be performed on-site and underwater, allowing a ship to return to commercial operations without the need to drydock.

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