Drivers for high-quality diesel fuel filtration systems
There are few areas in which vehicle filtration has become significantly more complex in the past two decades than in diesel fuel filtration.
The drivers of these requirements were, and are, the impressive technological optimisations of the injection systems. With the objective of increasing efficiency and minimising emissions, components and systems are being further refined and pushed to their technical limits. On the other side, their sensitivity to contamination increases. The system manufacturers are therefore forced to require high fuel purity levels when it enters the injection systems.
In addition, engines in use throughout the world come into contact with highly divergent fuel qualities which are also contaminated, to varying degrees, with particles and water. For many regions in the world, nearly unsustainable upper thresholds for the contamination of the provided fuels can be indicated. The same applies to contamination from solid particles which might come, for instance, from corrosion or wear and tear on upstream fuel provision systems. To a comparable degree, water contaminates the fuels.
Conclusion: The purity requirements for fuel prior to entering the injection system increase while increasingly critical assumptions, with respect to the fuel quality on the raw side, have to be made.
Requirements for particle filtration and water separation
The harmful impact of hard, abrasive particles is particularly critical for the functionality of the injection system components . The contamination of fluids is described in accordance with ISO 4406 by specifying purity classes for the particle sizes from 4, 6 and 14 µm . Today, injection system manufacturers require purity classes between 12 and 16 at 4 µm. On the raw side, the OEMs specify values between 18 and 25 at 4 µm. This means the fuel filter has to fulfil requirements with respect to the efficiency of the particle separation in the range of h (4 µm) = 99 … 99.5% or even higher.
Alongside the purity requirements with respect to solid particles, focus on the separation of water from the fuel has also increased. On conclusion, it can be stated that insufficient water separation leads to severe damage to the injection system, namely, due to corrosion, cavitation and wear and tear due to insufficient lubrication. In addition, water in fuel serves as the basis of life for micro-organisms and thus promotes microbial contamination.
Diesel fuels have complex designs. They contain bio-diesel components and additives which make water separation effectively more difficult. At the same time, water cannot be completely prevented from getting into the fuel, for instance, due to condensation in the tank. In practice, this is exacerbated in some cases due to an unfavourable layout of the tank ventilation.
Current requirements with respect to the efficiency of the water separation are often in the range of > 95%. In addition, water separation becomes less efficient if the media layers are contaminated by dirt particles after a certain period of use. Ageing effects can also have a negative impact on functionality. Current specifications sheets therefore increasingly demand verification that the water separation function remains constant throughout and beyond the entire service life of the filter or at the very least, does not decrease significantly.