Highly efficient protection

The fuel filter with three-stage water separation from MANN+HUMMEL reliably protects the injection system against particles and water.

Water in fuel can seriously damage the components of the diesel injection system in engines. MANN+HUMMEL has found the answer: three-stage water separation which successful retains even the smallest droplets.

"Imagine a lotus flower. Water droplets simply roll off the surface. A single-stage diesel fuel filter works in a similar way. But after a certain period of use, the water-repellent surface of the filter is too contaminated for it to do its job properly. Therefore, we had to find a different solution, like this." – Martin Veit points to a model in his hands. The senior product engineer is responsible for the basic development of three-stage water separation, a successful project at MANN+HUMMEL.


High requirements for fuel

In addition to dirt particles, water droplets have a direct effect on the components of the injection system. This is particularly true for modern common rail systems which require a high level of purity for the fuel. For this reason, the particulate filter has to be complemented by a so‑called water separator which reliably removes the water droplets from the fuel. This is no easy task which MANN+HUMMEL is up against. "Due to changes in recent years made to the composition of diesel fuel, these water droplets are very small and have a diameter of just a few micrometers. A simple strainer is not enough on its own. We have to work in stages", explains Veit.


Reliable removal of water droplets

This is possible with a diesel fuel filter which uses three‑stage water separation. In the first stage, the filter removes the dirt particles and protects the so-called coalescer against contaminants. The second stage involves water droplet coalescence where small droplets are combined to become bigger droplets which then enter an area with a reduced flow, the sedimentation opening. From there they fall with gravity into the water trap below the filter element. The third stage includes a hydrophobic barrier which retains the last remaining droplets. It guides the flow of the water to the water trap. In this way the water droplets are prevented from entering the injection system, and the filter can separate the droplets.

Separation of water

Coalescence of water droplets

Separation of particles

Further development

The multi-stage solution has previously been used in aerospace and hydraulic filtration applications. Then, some years ago, MANN+HUMMEL transferred the solution to cars and commercial vehicles for the first time. Today, MANN+HUMMEL continues to further develop its solutions for water separation with full commitment.