The importance of fuel filtration
Fuel contamination – the problem
There are numerous stages in the fuel delivery and storage process where there is chance for fuel to become contaminated with dirt, dust and debris. Sometimes to the naked eye fuel may appear clean. However, it shouldn’t be taken for granted that it is, as even the smallest of particles can lead to problems. Should there be any dirt or debris within the fuel, the particles can ruin the pumping equipment being used by breaking the pump’s vanes, or it can damage the internals of the vehicle being refuelled.
Although it is generally considered to be referring to particles, debris isn’t the only way in which fuel can be contaminated. The greater bio-content that is now present in diesel means that fuel, particularly fuel that is stored inside a bulk tank, often has small yet problematic amounts of water within it.
Due to its density, the water present in the fuel sinks to the bottom of the tank, creating an interface where the water and fuel meets. This interface is the perfect environment for bacteria, commonly referred to as “bugs in fuel”, to grow and feed. These bugs create a sludge or “bio-film” which can damage the vehicle or machinery that the tank is fuelling, causing costly downtime and equipment repairs.
It is therefore highly important that any fuel transfer system has some level of fuel filtration in order to reduce the risk of these problems.
Selecting the right fuel tank filter for your application
With the presence of both particles and water being a source of fuel contamination, best practice is to have both a water and a particle filter on your refuelling system in order to prevent both types of damage. Water filters do also remove a certain amount of particles; however they are not as efficient as a purposely designed particle filter. Particle filters however absorb no water, so if you have already have a particle filter and want to deal with the water in your fuel then you will need a separate filter.
Fuel tank filters also differ on the size of the particles that they can filter out of the fuel, which is measured in microns. The smaller the micron rating of a fuel filter, the smaller the particles it can remove. Essentially, the smaller the micron rating the better the level of filtration because it means it gets rid of small debris as well as just larger particles. Some vehicle manufacturers state that for the warranty to be valid a certain micron of fuel filtration is required.
The choice of fuel tank filter also depends upon the flow rate. In order for the filter to work, its flow rate must be compatible with the flow rate of the refuelling system it is being added to. For example, if you have a 56lpm fuel transfer pump, the fuel filter needs to have a flow rate range that deals with 56lpm. Some fuel tank filters such as Goldenrod filters are specifically designed for use with gravity fed installations, and are therefore able to cope with very low flow rates.
How does an absolute filter differ from a standard one?
As discussed, contamination particles are measured in microns, with filters having a micron rating to distinguish the size of the particles it can remove. Filters can also be looked at in terms of their efficiency; the percentage of particles in the fuel that the filter prevents from passing through the system.
A standard or a ‘nominal’ filter tends to be measured just by its micron rating as for most applications this is level of filtration is sufficient. However absolute filters are classified as being 99.95% efficient. In order words, if a 10 micron absolute filter is used, out of 100,000 10 micron particles 99, 950 of those 10 micron particles will be filtered out. In terms of absolute filtration, there is an ISO standard for diesel fuel cleanliness of ISO 14/13/11.
‘Absolute’ filtration is required in very specific circumstances; usually when the costs associated with damaged vehicles/machinery are too high. For example, where the downtime of equipment cannot be risked.