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fuel polishing

having had 2 cases of fuel contamination in 2 years,is fuel polishing as seen in WWDec the answer?
Geof Long

Asked by: Geof Long  | 3.12pm, Friday 12 November

WW says:

Fuel polishing is quite useful, however...
Interestingly, the main answer would seem to be samller fuel tanks, so you have a more rapid turnover of fuel...
Larger tanks are more likely to gain condensation, as the air inside expands and contracts, when it isn't full, drawing in moiture from the air. Smaller tanks tend to be less prone to this, and fresh fuel is constantly added.
Hot fuel that returns from the engine can also degrade the fuel, and, over time, this can lead to waxes forming, as the more volatile components vapourise off.
As changing the tank size is not usually possible, then the best idea is a good-quality fuel treatment agent. WW will be looking at various treatments soon- they are currently under test. Some conditioners improve the quality of the fuel, while others bind water, so it can be passed through. However, some agents added will only work if they are constantly agitated (like a yacht at sea, or a car/truck), but they can settle out in a narrowboat tank, becoming useless.
As well as fuel conditioners, buying good fuel (from someone who has a large turnover, is a good start), there are a few other things you can use:
Firstly, regularly drain the tank of accumulated water, BEFORE adding any treatment agent.
Fit a proper fuel filter and water seperator inline to the engine, before it reaches the engine final filter. You can add two cartridges, which filter to different specifications (such as 10 and 4 microns, down to 0.1 microns) which will remove any rubbish before it reaches the engine.
As the engine will pull a lot of fuel through that it doesn't use, and then return this to the main fuel tank, this has the effected of polishing the fuel.
However, many large seagoing yachts (such as the Nordhavn range) have a fuel polishing system fitted, that can deal with contamination aboard. One way to replicate this, is to run the engine from a small (say 25 litre) header tank, and top it up every day from the main tank, using a set of high quality fuel filters (just ensure the engine fuel return goes into the header tank, and is preferably cooled before returning).
I hope that helps- if I can go into any further detail, please let me know.

Mark Langley  | 5.08PM, Friday 12 November

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