Underwater propeller operations across Europe

In all cases the best solution was offered to the customer to restore the propeller’s efficiency as close to the original condition as possible.

Smoothing the creases

The propeller blades of a 180-meter bulker were severely bent. A fast, on-site solution to restore the propeller’s balance and efficiency was needed. Hydrex therefore sent one of their trucks with a team to the ship’s location in Ghent. .

After the equipment arrived, the team started the operation with a detailed survey of the ship’s propeller. This confirmed that all four blades could be straightened.

In close communication with the team leader in the monitoring station on shore, the divers correctly positioned the cold straightening machine over the propeller blades, to bend them back into shape. While the divers were repairing the propeller underwater, the team leader ashore monitored video links from underwater cameras on the divers’ equipment. This allowed them to communicate the exact dimensions and position of the damage between the divers and the technical team supervising the operation. This is essential because the calculations need to be perfectly accurate to achieve the best results in terms of propulsion efficiency.

When the straightening was complete, the technicians polished the blade to check for hairline cracks. The same procedure was then repeated on the other three blades. This was done without disruption to cargo operations or the vessel’s ongoing schedule.

The 163-meter reefer in Skagen only needed two of the five propeller blades repaired. Hydrex mobilized a team to straighten the blades using the same procedure as on the vessel in Ghent.

The cream of the crop

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 was the case for the operations described below.

With all four blades of a 245-meter tanker’s propeller severely damaged, the engine was overloading. Hydrex was asked to perform an on-site repair during the ship’s stop in Algeciras.

After the equipment arrived at the vessel’s location, the team started the underwater operation with a detailed survey of the affected propeller blades. This revealed that the tips of the blades were bent and chipped.

The information acquired during the inspection was then used by the team to calculate and determine the correct measurements needed to crop the blades.

Next the four blades were cut underwater, ground and polished using our patented blade repair tool.

Two of the blades of the 5-blade propeller of a 252-meter container ship in Antwerp had unfortunately suffered a similar fate. To keep the propeller’s balance, two other blades were cropped as well. Extensive calculations had to be made to take the right amount off each blade to prevent vibration.

In Croatia on a 60-meter yacht, three of the five propeller blades received the same treatment. The result was the same as in all the other operations: a propeller with its balance and efficiency restored.

Hydrex teams often encounter blades like this that have been severely damaged, chipped or almost completely broken off during ice navigation for instance, or by hitting debris in the water. In most instances they can still be repaired on-site by grinding and cropping the blades.

Conclusion

Over 50 years of experience with propeller repairs have given Hydrex the tools and know-how to offer fast repair and modification services to vessels around the world. All types of afloat and underwater operations can be carried out rapidly and efficiently.