The Wolfson Centre for Bulk Solids Handling Technology

Bulker propeller repair avoids costly drydocking

(Posted on 02/11/20)

Hydrex has performed a propeller blade cropping on a 180-meter bulker berthed in Ghent. The tip of two of the four propeller blades was severely damaged and needed to be cropped to restore the propeller’s efficiency. The trailing edge of the other blades had suffered cracks that needed to be repaired.

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 us to straighten damaged blades in-water, allowing commercial operations to continue without the need to drydock.

In the following example cropping was the only option as the type of damage to the propeller blade did not allow cold straightening. 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.

Two of the four blades of the bulker had lost part of their tip. An on-site solution was needed to restore the propeller’s balance and efficiency. A team was therefore mobilized from the Hydrex headquarters in Antwerp to the ship’s location in Ghent.

After the equipment arrived at the vessel the team started the operation with a detailed survey of the propeller blades. They used the information acquired during the inspection to calculate and determine the correct measurements needed to modify the propeller blades. The first blade was then cropped and ground to give it the correct radius. The opposing blade was modified using the exact same cutting line, to give the propeller back its balance.

When the cropping was complete, small cracks were grinded out of the trailing edges of the other blades. This was done to make sure that any remaining loss of efficiency would be minimal.

Over 45 years of experience with propeller repairs have given Hydrex the tools and know-how to offer fast repair and modification services to vessels. All types of operations can be carried out fast and efficiently afloat and underwater.

In this case the repair took less than a day. This prevented any unwelcome delay to the vessel’s schedule.