• Underwater propeller repairs with Hydrex new generation equipment

    Underwater propeller repairs with Hydrex new generation equipment

    06/03/2013

    Last month Hydrex diver/technician teams performed successful propeller repairs on vessels berthed in Antwerp (Belgium) and Rostock (Germany) and on a ship at anchorage in Fujairah (U.A.E).

    By taking advantage of the in-house developed cold straightening technique, damaged blades can be straightened underwater. This allows a ship to return to commercial operations without the need to drydock. Optimum efficiency of the propellers can be restored by bringing the blades back close to their original form.

    If straightening is not an option, the affected area on the blade will be cropped to restore the hydrodynamic balance. This kind of repair is carried out with the propeller blade cutting equipment developed by the Hydrex research department.
     
    Underwater propeller blade straightening in Rostock

    With three of the four blades of its propeller severely bent, a 180-meter bulker needed a fast, on-site solution to restore the propeller’s balance and efficiency. Hydrex diver/technicians are trained to carry out repairs underwater in the shortest possible time frame. A team was rapidly mobilized to the ship’s location in Rostock to perform a cold straightening of the blades.

    After the equipment arrived at the vessel’s location the team started the underwater operation with a detailed underwater survey of the damaged propeller blades. The inspection revealed that two blades had bent over 40° while a third one had bent no less than 85°. The fourth blade had only suffered some smaller cracks which could be ground away.

    The team then positioned the straightening machine underwater over the bends of the trailing edges of the first blade. In close communication with the team leader in the monitoring station on-shore, the divers applied pressure to return the bent blade to its original state. This procedure was then successfully repeated for the other damaged blades. Even the blade that had been bent almost 90 ° was returned to its original position with the new cold straightening machine. This restored the propeller’s efficiency.

    Afterwards a video and photo inspection was carried out to the approval of the attending surveyor.

    Underwater propeller blade modification in Fujairah

    A Hydrex diver/technician team mobilized to a 180-meter tanker at anchorage in Fujairah. The vessel had suffered damage to the four blades of its propeller and the owner wanted Hydrex to perform an underwater repair.

    An underwater inspection revealed that the blades had suffered smaller cracks and dents along their trailing edges. Because the damage to the blades was limited, the ship experienced no vibrations and only a small loss of performance. No straightening or cropping was required. The Hydrex divers therefore ground away the cracks and polished the edges of the blades. This gave the propeller back its original efficiency. It will also prevent further cracking.

    A representative of the vessel monitored the entire operation and was very satisfied with the result of the repair.

    Fast underwater propeller blade repair in Antwerp

    One of the four propeller blades of a 190-meter roro vessel was severely damaged. The owner of the ship contacted Hydrex on a Friday evening, looking for a solution. After proposing an on-site solution, Hydrex mobilized a team to ship’s location in Antwerp the next morning to carry out and underwater repair. This allowed the owner to keep his vessel on schedule.

    During the underwater survey of the propeller, the team discovered that the blade was bent on two different locations: on the trailing edge and on the tip. The bent on the trailing edge could not be straightened in its entirety. For this reason the team cropped a small portion of the damage and straightened the remaining area. The tip was restored to its original position completely. By doing this the greatest possible efficiency was achieved for the vessel.

    Conclusion
    Our R&D department is constantly looking into ways to enhance the available propeller repair techniques even further to improve our services. New models of both the straightening and the 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.

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