Dirty fuel can seriously upset any day on the water. Ask anyone who has had their engine sputter and die because of muck, or water, in the fuel. Been there....got the t-shirt!
Fuel contamination comes from two main sources, solid dirt/muck and water. Water is probably the easiest to understand and resolve. Most boats have a way of draining the water out from where it shouldn’t be.
Solid muck is much more of a problem. It can be loaded with the fuel or, worse, it can actually develop and grow onboard. The home grown muck is the result of diesel bugs breeding in your fuel tank and living on the fuel as food. Following the laws of nature, what goes in has to come out. In the case of diesel bugs this is a black fibrous gunk that can block a fuel system rapidly.
How to approach fuel cleanliness? Well in the case of fuel bugs, killing them with a biocide will get rid of the live ones, but their remnants need to be removed too. Happily, there are two forces of nature that can help you with contaminated fuel, gravity and centrifugal force.
Pic 1: ASTRA's Alfa Laval Purifier Pic 2: Fuel Transfer Pump and Day Tank
Gravity is the easiest to understand. Most contaminants are heavier than diesel fuel and will sink to the bottom of a tank by the action of gravity. If you are fortunate you can remove them. If you can’t remove the contaminants, they will remain in the bottom of your fuel tank just waiting to be stirred up by bad weather, to cause you problems just when you are trying to avoid some nasty rocks or some other navigational challenge.
Centrifugal force is the best and quickest force to use, but you need a piece of equipment in the form of a fuel purifier to harness it. A fuel purifier is a wonderful device whose internals spin at a very high speed and generate centrifugal force. The fact that water and muck is heavier than diesel fuel helps here also. The contaminants fly out to the outside of the device because they are heavier, and the cleaned fuel flows out of the middle.
Pic 3: Our Chief Engineer during refit & trials, John Aitken, pictured while cleaning ASTRA's fuel purifier
ASTRA, being the wonderfully capable vessel she is, has a fuel purifier, though there can’t be many ships of her size that have that benefit . However, be aware purifiers aren’t the easiest pieces of equipment to deal with, despite what the instruction manual might say. There is many a fuel purifier that has reduced a grizzled engineer to tears, including this one! Know your purifier well, go through the appropriate spells and rituals when starting it and all will be well and you’ll be blessed with clean fuel. Contributed by John Aitken, Chief Engineer, ASTRA.