Modern engines in commercial vehicles place high demands on diesel fuel filters. MANN+HUMMEL offers efficient water separation and an improved filter head to ensure the required fuel quality.

In cooperation with a well-known manufacturer of commercial vehicles, MANN+HUMMEL has developed the first standard fuel pre-filter with three-stage water separation. Series production will start in 2020 and there are plans to use the filter in Europe and parts of Asia. The pre-filter will also be used in industrial applications as a standard product.

 

Pressure drop minimized

The three-stage filter element reliably cleans the fuel and separates any water in the fuel for the complete lifetime of the filter element. In the first stage, the patented MULTIGRADE particle filter media from MANN+HUMMEL retains dirt particles. The second stage enlarges the water droplets to enable them to be separated, and in a third step the smallest water droplets are separated using a hydrophobic barrier.

The improved filter head also helps to ensure a reliable supply of fuel to the engine. The filtration specialist focused on reducing the pressure drop. This has been achieved firstly through use of a filter bypass valve which opens at 150 millibars to limit the total pressure drop in the system. Secondly the non-return valve has been optimized in order to reduce pressure drop. Here MANN+HUMMEL opted for a flap valve instead of a mushroom valve. As soon as fuel flows in, a spring steel flap with a rubber valve seat surface opens the boring. As a result, the pressure drop in the filter head can be reduced by approximately 30 percent. This leads to a considerably higher dust holding capacity before the filter bypass valve opens. The improved flow at the non-return valve in the filter head allows the filter in total to reduce the pressure drop by approximately 20 millibars. This means that significantly less fuel flows through the filter bypass valve. Hence the quality of the fuel is increased.

A further advantage of the new non-return valve is seen while using the hand pump. If the hand pump is used after the element is changed to fill the filter with fuel, the flap valve is better able to seal the channel than a mushroom valve. As a result, less fuel flows back and less pump operations are required to fill the filter with diesel.

Protection without wear

The metal housing of the spin-on filter is not coated with zinc in order to avoid a catalytic reaction with the fuel which can lead to the formation of deposits and therefore to increased wear of the injectors in the injection system. Instead, the inside of the housing is hot-dip aluminized to offer better protection against corrosion.

The combination of three-stage water separation and flow optimization in the fuel pre-filter increase the filtration performance for the entire lifetime of the filter. In comparison to other products available on the market, the water separation performance achieved by the filter at the time of servicing is considerably higher.