All you need to Know About Hull Fouling – Intertanko’s Guide

Intertanko has released a guide that provides guidance on the current antifouling systems available in the market and the operational challenges associated with performance measurement and hull management.  Before we dive deep into the concepts, let us throw some lights on the basics.

What is Fouling? 

Fouling is the term generally used to describe the settlement and growth of marine plants and animals on submerged structures of a ship or any waterborne craft.  These structures not only include ships’ hulls, piers, piling and oil rigs, but also the internals of pipework used to carry water as a coolant for shipboard propulsion and power plant.

Fouling can be classified into two broad groups:

1. Macrofouling – which includes plant (weed) and animal fouling.
2. Microfouling – which includes unicellular algae and bacteria (also referred to as ‘slime’).

Thus, these macro and micro growths on the ship’s hull increases the resistance and thereby the engines eat more fuel to overcome these gradual build of growth induced resistance.

Then came a new technology, where these growths are retarded by certain characteristics of paints which are generally referred as ‘anti-fouling’ paints.

Antifouling and Hull performance:

Anti-fouling paints are used to coat the boot-top and the wetted surface area of a ship to prevent sea life such as algae and molluscs attaching themselves to the hull – thereby slowing down the ship and increasing fuel consumption.  The new Convention defines “anti-fouling systems” as “a coating, paint, surface treatment, surface or device that is used on a ship to control or prevent attachment of unwanted organisms”.

With the introduction of the IMO’s Anti fouling Convention (AFS) in September 2008 and the subsequent banning of TBT, there exists a wide diversity of antifouling products.

The guide emphasises on the increasing need to undertake hull cleaning.  An increased focus on hull performance for improved vessel efficiency as well as the need to minimize the transfer of invasive species on ships’ hulls has seen the importance of antifouling coating selection elevated in many shipping companies.

Antifouling and fuel efficiency:

Antifouling has a direct effect on fuel efficiency.  The changes in the market, with vessel speeds now much lower strikes its importance on other fuel efficiency methods.  This speed regulation along with the regional biofouling legislation have led to an increase in underwater hull cleaning.

Effects of micro and macrofouling:

The term “grooming” is being used more frequently in the industry. Grooming removes micro-fouling and it is a quick, relatively easy technique.  If this technique employed and executed with perfection there will be no damage to the coating.

Cleaning of the macro-fouling on the other hand is slow, more difficult and will invariably damage the coating. Importantly from an environmental perspective, cleaning macro-fouling may also present a greater risk of invasive species dispersal as the organisms that would otherwise remain on the hull are being actively removed and could survive and find a new substrate to colonize in the local environment.

The table below demonstrates the significant effect on performance of slime.

Why is Hull Cleaning essential?

Hull fouling is not typically uniform, and more than one type of fouling is present, it is important that the hull grooming/cleaning company is aware of the ship’s expectations, before the job starts.  With 99 percent slime (micro-fouling) and one percent hard barnacles it can be argued that grooming is a mechanism of treating softly the 99 percent of the surface area.  By this treatment the barnacles are killed leaving the barnacle cement pads intact. This is the best choice compared with cleaning using rough, hard, abrasive discs to assure removal of all barnacle remnants besides that, it also damages the  surface.  There should be a conversation between the operator and the hull treatment diving company about the optimal solution and choice of brushes (or other tools), advises Intertanko.

You can download the Intertanko’s guide here

Every day there is a huge buzz of some new technology claiming to make a ship energy efficient.  While this could be true, it is necessary for every ship Manager to ensure that such new technologies indeed offer fuel savings.  The only way to ensure this is to have a simple, robust data augmentation tool like VEEMS (Viswa Energy Efficiency Management System).  There is always a need to have a proper tool to measure and check whether your ships are energy efficient.  It is for this reason, Viswa Lab has come out with a user-friendly, robust, data augmentation tool to measure a ship’s energy efficiency standards.

VEEMS has a tag line –

“Only if you can measure it, you can control it!”

There is always a need to have a proper tool to measure and check whether your ships are energy efficient.  It is for this reason, Viswa Lab has come out with a user-friendly, robust, data augmentation tool to measure a ship’s energy efficiency standards.

Feel free to download VEEMS (Viswa Energy Efficiency Management System) guidebook here

Below is a graphical representation of what would really happen to the fuel consumption over the years when the hull fouls.  This is where VEEMS can really help you to identify and quantify the increase in fuel consumption for a vessel by data augmentation.

The image shown below is a simple hand drawn conceptual trend where the x-axis represents time period in years and the y-axis is the fuel consumption.  The fuel consumption of a vessel increases over a period of time and it reaches a point where a decision was made to clean the ship’s hull and propellers.  The fuel consumption resumes to normal or near sea-trial data.  Further, as the ship trades over a couple of years the fuel consumption once again increases.  Thus, from the below area represented in green color, is the benefit acquired through fuel consumption as the hull and propeller cleaning was done at the right time instead of waiting for a apt dry-docking period.

The below image is a snapshot from the actual VEEMS system fitted on board a merchant ship.

The green vertical line is where the vessel carried out a propeller cleaning, after which there is a slight improvement in speed performance of the vessel.  Ideally, for the same amount of fuel burnt, the ship’s speed has increased which can be witnessed from the graph.

Thus, VEEMS is a powerful, user friendly, robust data augmentation tool, where it comes handy to quantify the fuel efficiency and energy savings what-so-ever may be the technology or methods employed.

Feel free to contact the VEEMS team to request for a demonstration by contacting us at experts@mfame.guru

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