Behr Hella Service
Behr Hella Service

Three-stage water separation

In recent years, modern diesel engines have achieved hugely enhanced performance and significant improvements in efficiency with regard to emissions behavior and fuel consumption. Ever higher injection pressures have resulted in increasing demands with regard to the separation of water contained in diesel fuel. In order to achieve reliable water separation through the use of a filter element, MANN+HUMMEL has developed a three-stage filter concept. After successful introduction in passenger cars, series production for a commercial vehicle product will follow at MANN+HUMMEL in 2017.

Water enters into the tank and the diesel fuel in several ways. Poor fuel quality with a high water content can be a cause, as can the ingress of water through the tank ventilation, or condensation from humidity. The consequences of this include corrosion and cavitation effects to injectors, valves and the injection pump. This may even result in system failure. Free water can also cause microbiological growth and corrosion processes. Here, there is a risk that the fuel filter becomes clogged prematurely and has to be replaced earlier. Furthermore, pitting corrosion can damage the filter housing and lead to leaks.

In order to achieve reliable water separation throughout the service life, MANN+HUMMEL has developed an innovative three-stage filter concept. In future, this will also be used in the latest fuel filter modules for commercial vehicles.

Here, the fuel flows from the outside to the inside of the filter element. In the first stage, solid particles are filtered out by the highly-efficient filter medium. A coalescer then combines the water droplets to form larger drops. In the third stage, the hydrophobic sieve prevents these enlarged drops from following the fuel into the injection system. This principle works thanks to tailored adjustment of the various components within the fuel filter element. The separated water itself is collected in the filter module, detected and then drained either manually or automatically. With the high achievable water separation efficiencies, the injection systems of the commercial vehicle engines can thus be reliably protected over the long term.

In the past, single-stage concepts were sufficient for meeting the water separation rates. A water-resistant coating was applied on the upstream side of the filter element for this purpose. This concept, however, is no longer able to cope with pressure-side filter operation and modern low-sulfur, biofuel and high additive-containing fuels. The injection system can no longer be effectively protected from damage by this means.

If water from the tank enters the fuel circuit, it is reduced to small droplets in the low-pressure fuel pump. The separation of small droplets poses a challenge for fuel filter systems. In the case of filter elements with a water-repellant effect only on the upstream side, the water separation rate is reduced with increasing loading of the filter element during use. The small droplets are no longer separated at the surface, but are forced through the pores of the filter medium owing to their small size. Particularly through additive components in biofuel and separated dirt particles, the hydrophobic properties are impaired to such an extent that water separation is completely lost over the service life of the filter element.

In contrast, MANN+HUMMEL achieves a 75 percent water separation over the complete lifecycle with its three-stage filter concept.

Διαχωρισμός νερού τριών σταδίων

chome L Sygrou 246 & Davaki
Kalithea , .17672
cphone  +30 210 9531690-5
cfax  +30 210 9531696-7
cmail  info@electra-hellas.gr

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