Hull cleaning

A ship owner is, principally interested in the potential savings associated with a clean hull and smooth propeller. Anti-fouling paints offer protection against marine growth which lead to increased resistance requiring additional power (fuel) to maintain the same speed. The greater the time spent at sea, the less the anti-foulant effectiveness. Ship owners should intervene to arrest this process which in turn would reduce navigational expenses.

The following 3 stages show the different depict the process of deterioration caused by Marine growth on ships and other vessels:

Phase 1: Various anti-fouling layers on the ship’s hull over time dissolve their toxins;
Phase 2: Soft marine growth consisting of algae, slime and immature barnacles start to adhere to the plating and penetrate the protective anti-fouling coatings;
Phase 3: Barnacles and tubeworms develop and attach themselves to the steel plating, causing permanent hull damage.

Prevention

In order to prevent this damage an overall clean should be carried out at phase 2. The required cleaning tools consist of a rotary cleaning system using soft nylon bristles. Triton Diving Services with its specialized divers use twin brush hull cleaning machines for which clean up to 800m²/hour.

Propeller polishing

The propeller is particularly vulnerable to marine fouling since it is an unpainted surface that must remain clean and shiny for proper operation.

By standards, we are aware that propeller fouling, despite its small surface area, can generate energy losses amounting to half that of the hull itself so maintaining a clean propeller is critical. Triton Diving Services insist that propellers are also polished routinely to reduce friction and ensure that the propeller operates at optimum efficiency. Even with routine maintenance, surface roughness can occur as a result of erosion, corrosion, or from tubeworm tracings.

This roughness alone can increase fuel consumption up to 10 %. Triton Diving Services use  underwater hydraulic operated rotary tool for the cleaning of propellers. The polisher is designed purposely for the cleaning and polishing of the propeller. Various flexible abrasive heads adapt to the structure of the propeller. Whilst the rotary motion creates a downward suction force, the diver monitors and steers the tool all over the blade, boss cone, blade edges, applying a number of discs to reach the required scale.

The preliminary job involves the removal of growth using an appropriate abrasive head. Once the growth is removed, the buffering is followed using very fine discs and polishes to approximately 1-micron C.L.A..The duration for a underwater polish of a 4/5 bladed propeller with a 6.5m diameter would be approximately 4 hours!