• Fast propeller repair in U.S.A. avoids costly drydocking

    Fast propeller repair in U.S.A. avoids costly drydocking

    30/10/2014

    Recently a team of Hydrex diver/technicians performed a propeller blade cropping on a 363-meter container vessel berthed in Oakland, California. One of the six propeller blades had partially broken off and needed to be cropped to restore the propeller’s efficiency.

    Having developed different procedures for different kinds of damage, Hydrex teams are equipped and trained to make the best out of a bent or broken propeller. Ideally, the in-house developed cold straightening technique is used. This procedure enables Hydrex technicians to straighten damaged blades in-water, allowing commercial operations to continue without the  need to drydock.

    In the following example cropping was the only option as the damage to the propeller blades was too great to allow cold straightening. This kind of repair is carried out with the propeller blade cutting equipment developed by the Hydrex research department. In cases where there is an even number of blades an identical piece will be cropped from the opposite blade to restore the hydrodynamic stability of the propeller. By doing so, the best possible efficiency is obtained.

    Underwater blade cropping restores efficiency
    One of the six blades of the container vessel had broken off. An on-site solution was needed to restore the propeller’s balance and efficiency. A team was therefore mobilized from the Hydrex office in Tampa to the ship’s location.

    After the equipment arrived at the vessel’s location the team started the operation with a detailed survey of the affected propeller blade. The team then used the information acquired during the inspection to calculate and determine the correct measurements needed to modify the trailing edges of the propeller blade. Next the divers cropped the blade and ground its edge to give it the correct radius. The opposing blade was modified using the exact same cutting line, to give the propeller back its balance.



    When the cropping was complete, the Hydrex technicians polished the blades to make sure that any remaining loss of efficiency would be minimal.

    Conclusion
    Our R&D department is constantly looking into ways to enhance the available propeller repair techniques even further to improve our services. New types of both the straightening and cutting machines have recently been put into service. These allow us to straighten blades that could previously only be cropped and to crop extremely damaged blades with only a minimal loss of efficiency for the propeller. Both types of repairs can be carried out rapidly and efficiently on-site and underwater, allowing the ship to return to commercial operations without the need to drydock.

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