solids from clogging pipes, filters and other system components.
However, the fuels made available to the latest standards (BS EN 2869:2010) include additives to manage CFPP and maintain stability. Experience will demonstrate whether these are sufficient to meet former expectations of fuel life.
The Regulations (and the fuel standards derived to meet them) also introduce a reduction in the level of aromatics within Diesel fuels. These chemicals are hydrocarbons of benzene ring form, that can be harmful to people and the environment. However, fuel system seal effectiveness relies, to some extent, upon the “swelling” effect that aromatics have upon the seals’ material. A reduction in aromatics may lead some seals to shrink, with subsequent risk of fuel seepage at flange/seal interfaces.
Conversely, some seal materials can be weakened by the bio-diesel content of fuel, which may also give rise to seal failure; with resulting fire risk. Careful inspection and replacement, at the first sign of seepage/failure should prevent a more catastrophic waste of fuel and environmental impact.
Current advice builds upon good engineering practice and includes ensuring that:
- in larger installations, consideration should be given to modifying the fuel system to include two stages with filtration and separation by coalesce or centrifuge;
- the fuel in any tank is ‘refreshed’ (turned over) regularly, at least every 3-6 months;
- tanks are kept as full as possible, to reduce condensation;
- any water content is drained off more regularly (although it is rarely possible to remove it all) in order to discourage MBC. Consideration should be given to modifying the drain facilities to make them more effective;
- seals and components (elastomer-based and rubber) in the fuel system are inspected and, where necessary, replaced at the earliest opportunity;
- strainers and filters are checked and cleaned more regularly;
- where MBC may be suspected, to undertake sampling and analysis.
This advice is easy to put into words, but far less easy in practice. For example:
- Some of the smaller marinas and boatyards, especially on the canal system, may have only one diesel storage tank and may not sell adequate quantities of fuel to allow the recommended ‘refreshing period’;
- Many inland waterways vessels and recreational craft are laid up over the winter with full or partly full fuel tanks, for 6 months or more in some cases. This is done out of convenience and to minimise condensation but where would you drain the fuel to, anyway? VAT and safety rules are strict about transfers of fuel out of a vessel.
If you are unfortunate enough to discover or suspect the presence of MBC in a bulk or vessel’s storage system, there is only one realistic course of action: to consult specialists.
There are systems available that allow fuel to be monitored for the presence of MBC, which can identify the type of microbe and give approximation to the severity of contamination. Conidia Bioscience Limited and ECHA Microbiology have systems, which have demonstrated to give rapid and effective results on-site. Other suppliers have systems available which will give effective results but which require time for laboratory assessment, before results can be known.
The remedy, where MBC is well established, must be to empty and clean physically the tank and
56 | The Report • December 2017 • Issue 82
then, in all cases, to treat the whole system and whole tank lining with biocides. Less serious outbreaks may be tackled with biocide additives, within the tanks and filtration. Some specialists provide a visiting, vehicle-based cleaning and recirculation system. Some companies suggest use of ultra- violet light to kill bacteria. However, such light can have the undesirable side-effect of breaking down antioxidation properties of the fuel.
Industrial, road and marine engine manufacturers and fuel injection systems specialists have been working with the fuels industry and standards bodies, for some years, in development of engines and fuel systems that are compatible with proposed new fuels, including those with bio-diesel content. Most new marine engines are designed to burn Ultra-low Sulphur (ULS - 10 ppm – also called “sulphur-free”) fuel with bio-diesel content up to 10% and there are current moves to ensure that forthcoming installations will be provided with Catalytic Emission Control Technology, in order to reduce substantially the polluting emissions. Development of these systems relies upon ULS fuel being widely available and used, as the sulphur of low-sulphur fuels (up to 1,000ppm sulphur – the previous standards for “Red Diesel”) would “blind” the catalysers and impact badly upon both emissions and engine performance. So, the introduction of ULS fuel is a good thing for the environment, which marine engineers and other professionals should promote.
However, it is a fact that a majority of engines on inland waterways vessels and many older recreational craft, especially those on the UK canal and river systems, come from a previous generation of technology, when Sulphur content of 1,000 ppm and above was normal (with inherent and known lubricating property and bio-poisoning advantages) and when no one had even heard of bio-diesel. Some of them are tens of years old (as are some of the
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