When all four propeller blades of a 100-meter general cargo vessel were severely bent, a repair was required by the classification society. Hydrex therefore performed a detailed video inspection, followed by a repair while the vessel was berthed in Ghent, Belgium.
To make a full assessment of the damage, the diver/technician team first performed a detailed underwater inspection of the blades. This revealed that one blade was bent over an angle of 15° while the other three were bent over an angle of 90°. Because the damage was too extensive, straightening these last three blades was not an option. To keep the balance of the propeller, it was decided to crop all four blades at the exact same position.
The information acquired during the inspection was then used to determine the correct measurements needed for the cropping. The area to be cropped was marked out on the four blades and verified. The team then cropped the blades one by one and ground their edges to give them the correct radius. When the cropping was complete, the Hydrex technicians polished the blades to make sure that any remaining loss of efficiency would be minimal.
This restored the propeller’s balance and brought its performance as close to its optimum performance as could be achieved. The job was completed on-site, saving the time, expense and extra work of drydocking the vessel.
Subsea World News Staff , May 04, 2012; Image: Hydrex