Underwater Propeller Blade Cropping in Uruguay Restores Efficiency
In November a Hydrex diver/technician teams performed a successful propeller blade cropping operation on a 229-meter bulker under difficult weather circumstances while the vessel was at anchorage in Punta Del Este. Because of the high swell, cropping was the only option.
When the propeller blades of the bulker got damaged, a fast on-site solution was needed to restore the propeller’s balance with a minimal loss of efficiency. This would avoid an extended off-hire period to go to drydock. A Hydrex team was therefore rapidly mobilized to the ship’s location in Uruguay. Here they met up with our local support base.
At the time of the repair there was a fast current. This meant that there was only a limited window available for our divers to safely perform the operation. Hydrex diver/technicians have experience with dealing with difficult circumstances while keeping to the highest safety and quality standards. They can carry out underwater repairs in the shortest possible time frame. Their expertise and experience allowed them to easily divide the operation in parts so that the cropping of the blades could be spread out over two days.
After the team arrived at the vessel’s location, they started the underwater operation with a detailed survey of the affected propeller blades. This underwater inspection revealed that three of the four blades were bent severely.
This kind of repair is carried out with the propeller blade cutting equipment developed by the Hydrex research department. The equipment is lightweight and can be mobilized together with the divers.
The team used the information acquired during the inspection to calculate and determine the correct measurements needed to modify the tip of the propeller blades. The repair proposal was then discussed with the class and the owner. After it was accepted, the divers cropped the damaged blades and ground their edges to give them the correct shape. The fourth blade, which had not been damaged, was also cropped to keep the propeller’s balance. When the cropping was complete the Hydrex technicians polished the blades to make sure that any remaining loss of efficiency would be minimal.
During the cropping a class surveyor was present. He gave his approval for the operation after a final inspection was performed.
Conclusion
Damaged propeller blades will have a performance below average and cause vibrations. 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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