Last Updated: Apr 2012
A barrier for retrofitting, especially for propellers, is determining whether an efficiency gain has taken place. In the absence of a monitoring system, it may not be possible to determine if there was an improvement. Such retrofitting would therefore need to be made in tandem with a performance monitoring system.
For hull blasting and application of new coatings, access to adequate dry docking facilities is problematic, and it does require vessels to be out of service while work takes place.
In-water hull clearnings, either by divers or robotic systems, is an option, but many ports have restrictions on these activities while ships are still in the water or in proximity of the port. In-water hull cleaning requires one to three days to complete depending on the hull cleaning method, size of underwater hull surface and degree of fouling. In-water propeller polishing is a common procedure, requires only one day while in port and can yield 5% improvement in ship performance when done at regular intervals.
The IMO has noted that the use of polymers, nanotechnology coatings, or air lubrication systems have yet to be "proven in service". It does see a lot of potential in this area, though, for reducing hull and propeller resistance, but also concludes that reducing resistance "will depend on both the ability to reduce the friction of clean hulls and significantly also on the ability to maintain performance over time".