Expert Teams Provide Underwater Propeller Services

Hydrex teams carried out a wide range of underwater propeller operations on tankers around the world.

Among them a propeller blade straightening on a 248-meter ship in Algeciras, Spain, a blade cropping on a 183-meter vessel in Flushing, the Netherlands, and a spinner cone (Propeller Boss Cap Fins –PBCF) replacement on a 110-meter vessel in Rotterdam, The Netherlands.

Underwater propeller blade straightening in Algeciras

With three of the four blades of its propeller severely bent, a 248-meter tanker needed a fast, on-site solution to restore the propeller’s balance and efficiency. Hydrex team was rapidly mobilized to the ship’s location close to the Hydrex office in Algeciras Spain to perform a cold straightening of the blades.

After the equipment arrived at the vessel’s location with one of the Hydrex workboats, the team started the repair with a detailed underwater survey of the damaged propeller blades. The inspection revealed that the three blades had suffered deformations along the trailing edges.

The team then carefully positioned the straightening machine over the bends of the trailing edges of the first blade and, in close communication with the team leader on the work boat, applied pressure to return the bent blade to its original state. This procedure was then successfully repeated for the other damaged blades, restoring the propeller’s efficiency.

Underwater cropping of damaged propeller blades in Flushing

Hydrex mobilized a diver/technician team to carry out a detailed inspection and necessary repair to the damaged propeller blades of a 183-meter tanker during the ship’s stop in Flushing.

To make a full assessment of the damage, the team first performed an underwater inspection. This revealed that all four blades had been damaged. The affected areas of the blades therefore needed to be cropped to restore the propeller’s balance. The team then used the information acquired during the inspection to calculate and determine the correct measurements needed to modify the trailing edges of the propeller blades. The area to be cropped was marked out on each of the four blades and verified. Next the divers 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.

Underwater Propeller Boss Cam Fins (PBCF) installation in Rotterdam

Hydrex was contacted to install a PBCF during an oil tanker’s stop in Rotterdam. After the team arrived at the vessel’s location with one of the Hydrex workboats, they started the underwater operation with a full inspection of the propeller. Next the diver/technicians cleaned the area where the spinner cone was to be installed. They then lowered the cone into the water and positioned it on the propeller. When this was done, grease was inserted in the space underneath the propeller cone for lubrication and the bolts were put on torque and secured with wire, finishing the installation of the PBCF. The Hydrex team worked around the clock to finish the operation as quickly as possible.

By performing the operation on-site and underwater, the owner of both tankers could immediately start enjoying the fuel savings the system offers. Otherwise he would have had to wait for the next scheduled drydocking to have the PBCF’s installed. This would have lost him up to two years of savings. Calculations show that he will have earned back the money of the underwater installation in about eight weeks, so the savings for the customer are substantial.

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December 20, 2013