Afloat Propeller Repairs by Hydrex
Recently Hydrex diver/technicians carried out afloat propeller repair work on vessels in Belgium and the Netherlands. In Antwerp the damaged blades of a 190-meter roro vessel were cropped, while in Amsterdam and Rotterdam the propeller blades of two 229-meter bulkers were modified to allow the ships to save fuel while sailing at lower RPM.
When damage to propellers occurs due to impact with ice and other debris, it is very much possible to get the propeller repaired and ‘Hydrex’ is a pioneer in carrying out such repairs.
Missing Propeller Blade Tip.
A ship with bent or cracked propeller blades might experience severe vibrations while sailing. The classification society might demand a repair before the vessel is allowed to sail on. By straightening the blades or cropping them, the propeller’s balance is restored, resulting in a green light from the Class for the vessel. Be reminded, such damaged propeller blades could increase fuel consumption drastically. A monitoring system like VEEMS (Viswa Energy Efficiency Management System) could spot and indicate the same immediately.
A propeller modification can easily be combined with any other maintenance or repair operation that needs to be carried out on the vessel. Thanks to the flexibility of the Hydrex teams impact on a sailing schedule can be minimized.
Hydrex team and equipment arriving on-site.
In the following case study cropping was the only option as the damage to the propeller blades was too great to allow cold straightening. This kind of repair is carried out with the propeller blade cutting equipment developed by the Hydrex research department.
Overnight cropping in Antwerp
Three of the five blades of a ro-ro vessel were severely bent, with one of these blades bent at an angle of 70°. 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.
Cutting the opposite blade of the damaged blade to keep the balance.
After the equipment arrived the team started the operation with a detailed survey of the complete propeller. The team then used the information acquired during the inspection to calculate and determine the correct cutting line needed to modify the trailing edges of the blades and remove the damage. Next the divers cropped the blades and ground their edges to give them the correct shape. The two undamaged blades also needed to be cropped using the exact same cutting line to give the propeller back its balance.
Smoothening 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.
Blade modification does not need to wait until drydock
A good example of this is the project that was carried out recently on two sister vessels. These 229-meter bulkers were going to sail at a lower RPM. A modification of the propeller blades’ diameter would allow them to save fuel while doing this.
Cropped and buffed propeller blade.
Hydrex mobilized a team to carry out the modifications while the ships were afloat. One operation was done in Rotterdam, the other in Amsterdam, but in both cases they were performed without disrupting cargo operations.
Another example are the preventive modifications that we made in Bremerhaven to the blades of three ice-going vessels. This was done by modifying the blades to a very specific design that made them less prone to damage while keeping the performance of the propeller as close to optimum as possible. The operation was performed in close communication with the manufacturer of the propellers.
Conclusion
Testing one of the cropped blades for cracks.
Over forty 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 operations can be carried out fast, fluently and efficiently afloat and underwater.
Did you subscribe for our daily newsletter?
It’s Free! Click here to Subscribe!
Ref.: Hydrex, Hellenics
