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What to do if your stored fuel becomes contaminated.

Having contaminated fuel can be expensive if it causes failure of the generator, heating system or engine that it feeds, but how can you find out if the fuel is contaminated and what should you do if you find that it is?

Firstly consider this most common contamination agent, which is water.

There are two main sources for water contamination, one is a failure of the tank to keep the weather out, which can be a split in the top of the tank for just someone leaving the lid off before rain, but far more common is water absorbed from the atmosphere which is always an issue as the vast majority of tanks are vented and hence moisture is drawn into the tanks.  Condensation is one problem, especially when we have cold nights and warm sunshine in the day, the other issue is that modern biofuel which is mixed into diesel (EN590 DERV) and gasoil (red diesel), is hygroscopic and over time will draw water directly from the atmosphere.

Water then exists in two forms within the tank, firstly as “free water” in the bottom of the tank and secondly held in suspension within the fuel itself. Identifying water in the fuel can be a little tricky, as it sits at the very bottom of the tank, it can be hard to see and suspended in the fuel it is invisible.

For a smaller domestic tank, there are various chemical pastes that can be applied to a stick and then pushed into the tank, it will change colour in the presence of water. A bit messy, but quite easy to do once you have bought the chemical paste. Our approach was to design a small device which is attached to a piece of string and dropped into the tank. After 24 hours, the device is retrieved and if it has swollen up, there is water in the tank. The device is a small fabric bag which is white in colour, so it will also show up any sludge contamination, which we will come onto.

A few pounds and available on Amazon, the Tank Sponge Indicator is a cheap and simple way to identify contamination in smaller tanks, but for a commercial or industrial scale tank of bigger than 10,000 litres, more sophisticated testing is probably more appropriate.

For a few hundred pounds, fuel testing can be carried out, with samples taken from various levels within the tank. Almost always, the highest contamination will be at the bottom of the tanks, as water has a higher density than fuel and water is usually the trigger for further contamination.

In all UK refined fuels, very small levels of water are naturally present, indeed it is almost impossible to remove completely. “200 parts per million” is the maximum allowed to keep fuel within specification, in our experience freshly refined fuel tends to range from 60 to 100 parts.

A simple test will tell you the levels of water and our standard practice is to use the 200 parts limit as a sensible upper limit for fuel which is being used in any high value of high risk environment.

Having confirmed water is present, what options are available?

Well for very small amounts, it may be the decision is made to leave it. Very low levels are common and the fuel take off point is usually higher than the bottom of the tank, so in theory if the contamination is below that level, it should not cause a problem.

One issue with that approach is that the level will keep rising…and when it does reach the level of the fuel take off, things can quickly break down. The other consideration is that when new fuel is delivered, it will do so via a high pressure fuel hose, around 10 times more than a standard garage forecourt. This will often stir up the contamination at the bottom of the tank and allow it to block up any filters that are in place to catch small amounts.

Removal of the “free water” is quite simple, for domestic scale tanks, any OFTEC registered Heating Engineer should test for water and remove as part of the annual boiler service. For larger commercial installations, expert Fuel Services companies will be able to remove any contaminated fuel, legally classify it as waste and remove from site. It is very important that any waste oil removed from a commercial site is done so by a registered Waste Carrier and that the waste is then taken to a certified Waste Transfer site to be processed. The Environment Agency have wide ranging powers to fine companies that don’t comply with the relevant legislation for waste fuel removal.

To remove suspended water is almost never worth doing in small domestic tanks, it is cheaper to remove the fuel and start again, but for larger commercial and industrial sites, the option exists for fuel filtration and conditioning onsite. Companies like Craggs Environmental will come to the site with the required specialist equipment to filter the fuel and bring it back into the required specification. It is necessary to remove the highly contaminated fuel at the bottom of the tank before this process is undertaken, but usually both services are done on the same visit.

Once the fuel is returned to specification, keeping it that way is really just about good housekeeping. Annual testing can keep an eye on the problem, but for any higher risk environment, the best way to keep the fuel fresh and ready for use is to install a small filtration unit, similar to the large one which will have been used for fuel conditioning, which can then be remotely monitored to keep an eye on any contamination levels and by replacing the filters as required, the risks of system failure are minimised.

What of other types of contamination?

Well the second most commonly seen issue is a black sludge like substance, known as diesel bug. Present in all mineral fuels, these bugs are microscopic organic organisms that cause no problems in clean fuel. The issue is when the fuel comes into contact with water, it causes the tiny bugs to clump together, forming a black, slimy sludge which blocks up fuel filters at an alarming rate.

The best way to avoid the problem is to keep the water levels to a minimum, the treatment is exactly as for water.The best way to avoid the problem is to keep the water levels to a minimum, the treatment is exactly as for water.

Other types of contamination are far less common, and are much harder to identify. We have seen examples of chlorine in a large fuel tank, which was just a mistake from the site management team, but caused a huge problem. The only way to check for this level of contamination is a full chemical analysis of the fuel, which whilst not that difficult to do, is more expensive than the more usual water tests.

These types of contamination usually require removal of the whole tank of fuel as it can’t be easily removed. Failure to deal with high levels of chlorine or sulphur, or any other similar contaminant will draw the attention of the EA, but fortunately this is a quite a rare occurrence.

So in summary, whether you are a homeowner using oil to heat water or you house, or if you are a major organisation that stores oil for standby power generation, industrial heating or propulsion, managing contaminated fuel is something that deserves a bit of attention. The starting point is to test for the obvious issues and go from there, but ignoring the problem is storing up some much bigger, and much more expensive problems later.

Chris Bingham – Craggs Environmental, CEO

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