Recently Hydrex teams carried out underwater propeller operations in Belgium and Spain. In Antwerp the bent blade of a 197-meter dry cargo vessel was straightened. In Algeciras a 183-meter chemical tanker had four of its five propeller blades cropped. Both repairs were carried out on-site and underwater.
Underwater propeller blade straightening in Antwerp
One of the blades of a dry cargo vessel’s propeller was severely bent. The others propeller blades were also damaged, but less severely. A fast, on-site solution was required to restore the propeller’s balance and efficiency. A Hydrex team therefore mobilized rapidly to the ship’s location in Antwerp.
The team started the underwater operation with a detailed underwater survey of the damaged propeller blades. Next the team positioned the straightening machine over the bends of the trailing edges of the first blade. The blade was then returned to its original state. The other blades were not bent. They had however suffered smaller cracks and dents along their trailing edges. The Hydrex diver/technicians ground away the cracks and polished the edges of these blades. This restored the propeller’s efficiency.
At the same time part of the team removed the rope guard of the vessel. This was necessary because it was damaged by a rope tangled around the stern tube seal assembly. After the team removed the rope, they installed a new rope guard.
Both parts of the operation were carried out simultaneously, without any loss of time for the owner of the vessel.
Underwater cropping of damaged propeller blades in Algeciras
Last month a diver/technician team carried out a propeller blade cropping in Algeciras on a 183-meter tanker.
The equipment arrived at the vessel’s location with one of the Hydrex workboats. The team then started the underwater operation with a detailed underwater survey of the damaged propeller blades. The inspection revealed that four of the five blades had suffered deformations along the trailing edges.
Cropping the affected areas of the blades was the only option. This would restore the propeller’s balance. The team then calculated the cutting line needed to modify the trailing edges of the propeller blades. The area to be cropped was marked out on the four blades and verified. Next the divers cropped the blades one by one and ground their edges. This gave them the correct radius. Finally, the Hydrex technicians polished the blades to minimize any remaining loss of efficiency.
Damaged propeller blades will have a performance below average. The engine will have a higher work load. This results in increased fuel consumption and added stress. By taking advantage of Hydrex’s in-house developed cold straightening technique, damaged blades can be straightened underwater. In this manner optimum efficiency of the propellers can be restored. 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. These repairs are carried out with the Hydrex propeller blade cutting equipment. Both types of repairs can be performed on-site and underwater. This allows the ship to return to commercial operations without the need to drydock.
Press Release, December 07, 2012