Propeller polishing

The measure is related to the condition of the surface of the propeller which influences the efficiency of the propeller. The surface of a propeller will become less smooth due to strain and cavitation damage, whereas growth will start to develop over time. The potential fouling can be avoided by regular polishing or coating of propeller. It is recommended to perform this measure twice yearly. This has been found to have the optimal balance between cost and effect.

Applicability and assumptions

Propeller polishing is applicable for all vessels and vessel ages. The propeller may be polished twice a year. This is either performed by a diver while the ship is berthed and loaded cargo or when the ship is in dry-dock. The fuel cost for the ship will be reduced from improved propeller efficiency since the power loss in the system will be decreased.

The waters in which the ship operates will have a large impact on the effect of the measure. Waters with a high degree of fouling and algae growth will provide relatively higher savings compared to areas with less algae growth. Vessels that lie a lot at rest will also generally achieve higher reductions than more mobile ships, due to greater fouling rates. However, there are usually port restrictions related to propeller polishing due to fears of contamination by foreign organisms and algae growth.

Cost of implementation

Depending on the number and the complexity of the propeller(s), the cost of having a diver performing propeller polishing is in the range of $4,000 – $8,000 (USD).

Reduction potential

The reduction potential is dependent on vessel size, segment, operation profile and trading areas. The likely reduction potential of propeller polishing is between 3 – 4% on main engine fuel consumption.

On an annual average 0.5 – 3% fuel savings would be expected.

Other References

1. Wilkinson, C.P. (1994). Reductions In Fuel Consumption As A Result Of In-Water Propeller Polishing. The effectiveness of propeller polishing on the reduction in fuel consumption is reviewed from a theoretical viewpoint and compared with a number of actual trials carried out on several types and classes of ships.
2. Sherbaz, et al. (2012). Operational options for green ships
3. Koboevic, et al. (2018). New approach to monitoring hull condition of ships as objective for selecting optimal docking period
4. Dive Inspect Panama