The company in this case study is an international ship management organisation.
This study describes general problems with propeller fouling, the installation of our system on this vessel, and the results observed eight months after installation.
The propeller is a crucial component of a ship’s propulsion system and is custom-made, calibrated to the millimetre for each vessel. All specifications are tailored to the ship’s operations and characteristics. Many factors are taken into account: the complex hydrodynamic shape of the hull, the desired sailing speed, the ship’s tasks, and the waters it operates in.
All these variables influence the propeller’s design: height, width, thickness, and blade angle are optimised to minimise fuel consumption and maintain the most efficient speed.
Fouling on the propeller can, in extreme cases, lead to efficiency losses of over 30% compared to a clean, fouling-free propeller. Even small amounts of fouling affect fuel consumption. Biofouling therefore has a direct impact on operational costs.
In many cases, fouling is removed using a high-pressure cleaner while the ship is in dry dock. If waiting for the next dry dock is not an option, propellers are also regularly cleaned underwater. For some vessels, propeller fouling becomes a problem after just three months, particularly in sensitive conditions. This maintenance is costly and can negatively affect long-term propeller performance.
This case study focuses on the propeller of a large bulk carrier with a diameter of 8.4 metres. The vessel experienced fouling on the propeller, leading to unnecessary maintenance costs.
In addition to the cleaning costs, physically cleaning (sanding or polishing) the balanced blades underwater is undesirable, as it can damage the propeller surface and affect fuel efficiency.
The shipowner decided to test the Ultrasonic Anti-Fouling System on the propeller of this large bulk carrier, as the system had never been tested on the propeller of a vessel of this size before.
By preventing fouling on the propeller and eliminating the need for frequent cleaning, fuel consumption can be kept stable. The Ultrasonic Anti-Fouling System provides this solution.
The system consists of a control unit and one or more transducers, which generate an ultrasonic sound wave on the surface of the structure. This creates microbubbles that implode, targeting the first stage of fouling: the attachment of single-celled organisms that form the biofilm layer. By preventing this layer from forming, multicellular organisms such as mussel or clam larvae cannot attach. The system is therefore a preventive, environmentally friendly, and sustainable solution.
For this installation, the system was used with eight transducers: four on the aft bearing of the propeller shaft and four on the intermediate bearing.
The system must remain switched on at all times, continuously emitting the ultrasonic signal. The signal is particularly effective along the propeller shaft when the ship is stationary, which is also when fouling develops fastest due to the lack of water flow.
When the vessel is idle, the hydrostatic bearing’s oil film is inactive, allowing the ultrasonic signal to transmit more efficiently through direct contact between the shaft and the bearings.
Correct installation is essential for effective transmission of the ultrasonic signal. While installation is not difficult, careful attention is required when positioning the transducers and gluing the rings. For this part of the installation, we always recommend consulting Lamers System Care.
Approximately eight months after installation, the vessel entered dry dock for propeller inspection. The client was reasonably satisfied with the results.
As shown in the images, the propeller blades show no hard fouling (such as shells or tube worms), only some seaweed that can be easily removed.
Some light fouling is visible on the propeller shaft, which the client reported was simple to remove.
