Hull cleaning

Diver performing underwater hull cleaning

Diver performing underwater hull cleaning, Source: Hydrex

The purpose of underwater hull cleaning is to remove biological roughness or fouling. A build-up of marine fouling can lead to increased drag, resulting in a detrimental impact on a vessel’s hydrodynamic performance and hence the relationship between speed, power performance and fuel consumption.  Fouling, particularly in the case of a prolific build-up of hard or shell fouling like barnacles or tubeworm, can cause turbulence, cavitation and noise, frequently affecting the performance of sonars, speed logs and other hull mounted sensors.

Proper cleaning removes all traces of fouling and does not remove or damage the coating or cause any increased surface roughness. Underwater cleaning is performed either by a diver with brushers or by a remotely operated vehicle (ROV) controlled from land.

Applicability and assumptions

Hull cleaning is applicable for all vessel types and ages. Depending on the degree and type of fouling to be removed a diver can typically clean 200 to 400 m2 per hour of flat surfaces (less on the bow and stern areas). The operation will be performed during normal ship stops (bunkering, anchorage, waiting for canal passage, etc.). The fuel reductions depend on the extent to which the hull is fouled.

Cost of implementation

The price of hull cleaning will depend on the selection between a diver and a ROV, in addition to the vessel size. Total cost will be in the range of $5,000 to $50,000 (USD).

Reduction potential

Depending on the degree of marine fouling, vessel size, vessel segment, operation profile and trading areas a reduction in the range of 1% to 5 % on main engine fuel consumption can be expected.