We've recently undertaken quiet a lot of research into the effects of diesel bug and bio fuels. The result has been published in Waterways World, as can be seen below.
Already three marinas have identified (independently) that there is an issue with the bio fuel and fuel set. All three report having several cases of emulsification following fuel set treatment where bio fuel had been added. The marinas have been given advice as to how to sort this problem out but it goes to prove that the problem exists.
Diesel Bug, Water Contamination and Bio Diesel
With the recent introduction of Bio Diesel the confusion surrounding what is best practise and how to deal with situations which are affecting more boaters has lead to RCR provide the following guidance.
Fuel Tank construction in boats
Fuel tanks in boats are usually constructed so that the outlet pipe for the fuel system is located approximately 1-2 inches above the bottom of the tank. The reason for this construction is two fold.
1) Most tanks are metal and therefore over time fuel /water/ air results in corrosion and rust build up, this debris drops to the bottom of the tank and remains there.
2) The water which is present due to condensation and water ingress in the fuel tank naturally separates out and drops to the bottom of the tank when left to stand.
In both these cases the outlet pipe position ensures that neither water nor debris is passed though the fuel system providing protection from these types of issues.
The easiest method to identify how much fuel/water is in your tank is to use a clear plastic hose, drop this in to the tank being careful not to disturb the fuel , and when you feel the bottom place your thumb over the end to seal it and withdraw the hose. This should provide you with a sample of the tank and will show the amount of water present, along with an indication of any diesel bug contamination.
We recommend that you :-
- Dip your tank regularly and where water is present remove it, this can be done simply and cheaply using an oil extractor or electric pump, by pushing the pipe down to the layer of water and extracting water until the diesel comes though. Alternatively visit one of the Marina’s who offer a fuel polishing service.
- Regularly check your filler cap seal and replace if worn, cracked or damaged. Also if it has been raining the cap sits lower than the deck so wipe over to remove excess water before opening the cap.
- If you have a water trap filter, check and empty regularly, so that it is effective.
- Either leave the tank empty during winterisation and remove any water on your return, or leave the tank full and treated.
The advice above will combat both diesel bug and Bio diesel issues and water contamination removing almost all risks without the need to treat the fuel.
Water in Diesel
All diesels contains some element of water. Water content in diesel makes the diesel murky or cloudy and can be the first indication of an issue.
However when diesel is standing this water separates naturally (around 800ppm 0.08%) and as it is heavier than diesel it eventually drops to the bottom tank. This is why many commercial storage tanks have taps at the bottom to drain off the water.
Water in fuel is acceptable in small amounts and has been known to improve performance when in quantities of up to 1200ppm (0.12% volume), however there is a risk that too much water (greater than 1500ppm (0.15%) will result in the water lying un-burnt in the combustion chamber and affecting the operation of the pistons, valves, liners, ect by destroying the lubrication properties of fuel
In addition, too much water in the fuel can cause issues even before this point, as the injectors pressurise the diesel to turn it in to a fine spray, if there is too much water present in diesel then emulsification occurs and the white creamy solution that results will stop you in your tracks.
What is Diesel Bug
Diesel bug is the term given to the enzymes, bacteria etc that live of the water in diesel and affect the diesel properties, and there are over 148 different types identified so far. The first signs of fuel degradation are a fine black dust that is regularly described as soot, a very strong smell of varnish coming from the fuel tank and the fuel turning darker.
Visible sludge and other lesser known variations of diesel bug that can show as yellow/orange or pale debris floating in the diesel is an indicator of severe or high risk contamination and should be treated as soon as possible.
Extreme cases see this develop in to a thick black sludge that quickly clogs up the fuel system and stops the engine operating.
Bio Diesel & Low Sulphur Fuels NEW EU Directive
The introduction of the new rules relating to supply of diesel for recreational boats has stipulated that from 2011 it is an offence to sell diesel that contains more than 10mg of sulphur per kilogram of diesel, this effectively makes the fuel virtually ‘sulphur free’.
Diesel which is low in sulphur can cause issues with rubber and plastic components in the fuel system because is contains less lubricants, and eventually this lack of lubrication can result in faster degradation of these components, resulting in fuel pump and seal failures.
To accomplish the low sulphur content many suppliers have opted to incorporate Bio Diesel, (when biodiesel is blended, fatty acid methyl esters (FAME) are added to the mineral diesel) the recommended maximum is 7% although this will rise to 12% in 2012. The previous level was 5% and the new increase has resulted agricultural users seeing a fast rise in both diesel bug contamination and fuel blockage issues. This has been attributed to the fact that Bio diesel absorbs ‘free’ water, and this is what diesel bug requires to live on, but it can also result in emulsification of the diesel if too much water is absorbed.
Bio diesel only has a shelf life of approx 6months, put it in a marine environment and this half’s and if microbes like diesel bug are present it half’s again, potentially you may only get a few months shelf life!
*100% true bio fuel ie biodiesel produced strictly according to EN14214 standards does not tend to suffer the issues identified above and is a true green alternative which has many other benefits not seen with bio diesel mixtures.
The treatments on the market at present have concentrated on two issues, removing water from the diesel and killing diesel bug. There are many different products on the market but these can be split into Biocides and Enzyme based products. Each tackles the issue in different ways.
With any treatment; it is important to ensure that the product is mixed with the fuel evenly, and therefore treat before filling up, or alternatively give the tank a stir to ensure that the product is effective. If using enzymes it is important not to overdose as this can result in excessive water retention in the diesel.
These are chemically produced products designed to deal with specific issues. They can be used as a one off to treat diesel contamination (diesel bug killer), or dosed to prevent contamination occurring. These include products like M16 Diesel Bug, Grotamar, Yachtcon, Kathon, In general they contain biocide to kill micro bacterial contamination and inhibit further growth of micro bacteria. In some products they include demulsifies to separate out the water from the diesel , and lock in the dead bug ‘bodies’ in the fuel so that they are burnt in the combustions cycle, effectively removing the ‘sludge’.
Biocides are toxic and therefore should be treated with care and applied strictly according to the supplied instructions. When treating for fuel contamination then it is always advisable to change your filter and remove any water form the tank and water separator. However please ensure that the water is disposed of in accordance to the EU Biocide Directive.
There are many worries relating to bugs building an ‘immunity’ to these biocides, however in reality as all bugs are destroyed rather than treated, the analogy with antibiotics is not applicable.
Enzyme and Natural Emulsifier Products
These products are generally environmentally safe and are based on a combination of manmade enzymes and plant extracts, they tackle the issue by distributing and locking the water in to the fuel so that it can be burnt during the combustion cycle, by removing the water they remove the food for the diesel bug. If dosed correctly then the maximum water absorption should be in the region of 900ppm (0.09%) for the natural emulsifier products, which is safe; however if overdose this can raise to 2500ppm resulting in diesel turning milky. These include products like FuelSet, Fortron, Soltron and Starbrite. The other group of enzyme based products use Kerosene as a carrier and while this restrict the ability to absorb water kerosene has a much higher wax content. Overdosing with these types of products can lead to change in fuels ability to combust quick enough and cause injector damage.
Some enzyme based products are temperature and UV sensitive and this can cause them deteriorated or stop working effectively if subject to extreme temperature variations and if they are not stored properly. They are not suitable for treating severe diesel bug contamination and are only effective as a preventative maintenance solution. Overdosing is the biggest risk with these products.
Emulsification of Diesel
Too much water in the diesel can cause emulsification, this is seen at the filters or more commonly at the injectors as the fuel is put under pressure. Emulsification of diesel at the injectors due to water content has only recently become an issue and RCR in the past 2 months have attended nine boats where 20-40ltrs of bio diesel has been added to the fuel tank, in some cases these vessels have been using regular treatments of enzyme based products. Initially we were unable to resolve and the first three boats had to have the whole system cleaned and flushed, although in one case the diesel destroyed the seals in the fuel polisher, and resulted in over 200ltrs of fuel being lost!
To combat this issue we have had to develop a new strategy and after a number of test cases we now use biocide treatments to separate out the water from the diesel whilst in the tank, although because of the complex nature of the mixture this can take up to 48hrs to accomplish. Following this the fuel system is cleaned right though to the return pipes, and the water drained off from the fuel tank to remove the risk of the water being absorbed in the future.
So what treatment should you use:
RCR attends hundreds of contamination issues each year and therefore we have had to ensure that the product we use provides instant results and stops these problems from reoccurring, and for this reason we favour the Biocide treatments. Enzyme based products are effective and useful when there is only a small amount of water content but too much and you run the risk of not removing it or overdosing and locking to much water in to the diesel.
Another reason for favouring the biocide treatment is with the new introduction of Bio diesel and rise in cases of emulsification at the injectors, we believe enzyme products can compound the problem of water absorption.
RCR use Marine 16 products and recommend the use of Diesel Fuel complete as a regular treatment. However the most important message to get across is to regularly check your tank for water and if found remove it, doing this will reduce the risk of water contamination and diesel bug irrelevant of which product you choose to use.
Stephanie Horton BEng Hons CEng MIET
MD of River Canal Rescue
Acknowledgment:- David White of M16, Ian Roos of FuelQC, and background support from David Fletcher NABO chairman, EU Directive, Tony Brooks training notes