In International Shipping News 26/07/2016
Source: Hydrex
Recently a team of Hydrex diver/technicians performed a propeller blade cropping on a 190-meter container bulker berthed in Hamburg. Two parts of the tip of one of the four propeller blades were damaged and needed to be cropped to restore the propeller’s efficiency.
Having developed different procedures for different kinds of damage, Hydrex teams are equipped and trained to make the best out of a bent or broken propeller. Ideally, the in-house developed cold straightening technique is used. This procedure enables Hydrex technicians to straighten damaged blades in-water, allowing commercial operations to continue without the need to drydock.
One of the propeller blades was missing parts of its tip.
In the following example cropping was the only option as the type of damage to the propeller blade did not allow cold straightening. This kind of repair is carried out with the propeller blade cutting equipment developed by the Hydrex research department. In cases like this, where there is an even number of blades an identical piece will be cropped from the opposite blade to restore the hydrodynamic balance of the propeller. By doing so, the best possible efficiency is obtained.
Hydrex team and equipment arriving on-site.
Single day operation restores efficiency
One of the four blades of the bulker had lost two parts of its tip. An on-site solution was needed to restore the propeller’s balance and efficiency. A team was therefore mobilized from our headquarters in Antwerp to the ship’s location in Germany
Cutting the opposite blade of the damaged blade to keep the balance.
After the equipment arrived at the vessel’s location the team started the operation with a detailed survey of the affected propeller blade. 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 blade. Next the divers cropped the blade and ground its edge to give it the correct radius. The opposing blade was modified using the exact same cutting line, to give the propeller back its balance.
Buffing one of the cropped blades to achieve the best possible efficiency.
When the cropping was complete, the Hydrex technicians buffed the blades to make sure that any remaining loss of efficiency would be minimal.
Cropped and buffed propeller blade.
Conclusion
Over forty years of experience with propeller repairs have given us the tools and know-how to offer fast repair and modification services to vessels around the world. All types of operations can be carried out fast, fluently and efficiently afloat and underwater.
Testing one of the cropped blades for cracks.
In this case the repair took less than a day. This prevented any unwelcome delay to the vessel’s schedule.
