Last month a team of Hydrex diver/technicians performed a blade modification on the propeller of a 190-meter bulk carrier in La Brea, Trinidad and Tobago. All five blades of propeller were severely bent and cropping was the only option.
Hydrex has developed a wide range of procedures to repair all types of propeller damage underwater. If possible the in-house developed cold straightening technique is used. This enables Hydrex to straighten damaged blades in-water, allowing commercial operations to continue without the need to drydock.
In the following example, however, 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. By doing so, the best possible efficiency is obtained.
The blades of a bulk carrier’s propeller were severly bent. A fast, on-site solution was needed to restore the propeller’s balance and efficiency. A team was therefore rapidly mobilized to the ship’s location in La Brea to restore the damaged blades to as close to their original condition as possible.
After the equipment arrived at the vessel’s location the team started the underwater operation with a detailed survey of the affected propeller blades. The inspection revealed that all five blades were bent over angles of up 90 degrees. Additionally, one of the blades had suffered small cracks on its leading edge. The team used the information acquired during the inspection to calculate and determine the correct measurements needed to modify the trailing edges of the propeller blades.
Next the divers cropped the blades and ground their edges to give them the correct radius. When the cropping was complete, the Hydrex technicians ground the cracked edge of the last blade and polished all blades to make sure that any remaining loss of efficiency would be minimal.
The operation returned the balance and the efficiency of the propeller. By carrying out the cropping onsite and underwater, Hydrex avoided a costly and time consuming drydock visit for the owner of the vessel. The bulk carrier could continue her schedule without going off-hire and with the performance of her propellers restored.