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Biofouling is the word for everything that grows on a Hull in the sea. It begins within hours of a ship stopping and grows as long as the water is warm and the coating is weak. Biofouling removal in Nagoya Port is about knowing what you are dealing with and removing it in the right way.
The first layer is a thin film of bacteria and algae, often called slime. It feels slippery and looks brown or green. Next come soft growths such as weed and hydroids. After weeks, hard organisms such as barnacles, tubeworms and mussels settle and attach with cement that is hard to remove. Each layer makes the Hull rougher and the next layer easier to attach.
Fouling raises resistance and fuel use, and it blocks sea chests and gratings, which can affect cooling water flow to the engine. It also hides the plating, so the surveyor cannot see damage. A further concern is the movement of species between ports. Organisms carried on a Hull may survive and spread, which is why the IMO issued guidelines on biofouling management in 2011.
Slime and soft growth can usually be removed with brushes or cloths. Hard growth needs stiffer tools. The more fouling there is, the more force it takes, and the more risk to the coating. This is why cleaning early and often is gentler than waiting. A ship that is cleaned every few months needs only a light touch.
The Diver starts with a short survey of the Hull on camera, noting the type and amount of fouling. He then selects tools to match. Cleaning proceeds in sections from the waterline down, so that debris does not fall on areas already done. The supervisor watches the video feed and confirms that the coating is not being damaged.
Port and coastal authorities in different countries have different rules on cleaning in the water. Before we start in Nagoya, we ask the agent which requirements apply at the berth and plan the work to match them. Where debris must be captured, we use suitable equipment. If cleaning is not allowed, we say so and suggest an alternative.
We record the type and extent of fouling, the areas cleaned and the method. This supports the ship's biofouling record book and shows the technical manager how fast the Hull fouls on a given route and season. Our report format is simple and ready to be filed.
Fouling removed from the Hull falls into the water. Soft growth disperses quickly, while shells and scraped material settle on the bottom nearby. Some ports require the material to be collected, and we use suitable equipment when this is needed. We also avoid cleaning in locations where the rules do not allow it. If we are unsure, we ask the agent and the port side before starting the work.
Fouling in the Nagoya area is heaviest in the warm months, when water temperatures are high and growth is rapid. In winter, growth slows, and cleaning can be less frequent. An inspection before a long voyage is sensible in any season.
Q1. In what order does fouling develop on a Hull?
First a thin film of bacteria and algae (slime), then soft growth such as weed, and after several weeks hard growth such as barnacles and tubeworms.
Q2. When were the IMO biofouling guidelines issued?
In 2011. They recommend a biofouling management plan and a record book on board.
Q3. What parts of the ship do fouling problems affect besides the Hull?
Sea chests and gratings, which can restrict cooling water flow, and the propeller, which loses efficiency.
Q4. Does biofouling removal need local approval?
Rules vary by country, port and berth. We confirm the requirements with the agent before starting the work.
