Filter
What can be interesting at a filter? It keeps away from the engine even the smallest particles and thus prevents corrosion and wear. Then there'd be enough, you would specify to each filter a maximum size for
particles which just barely slip through. But is not quite right, because there is in addition a percent value.
So was the requirement of the manufacturer from a diesel engine a long time ago: 4 thousandths of a millimeter (µm) at 50 percent non-passage rate. By the way, a human hair has a diameter of 60 thousandths of a
millimetre. Currently less than 4 µm particle sizes are no longer measurable.
But what does this strange percentage? You have to know that a fleece is simply not a sieve. It would not be to accept that each sieve opening clogged little by little and the pressure required to flowing through rises
slowly. Somewhere must finally remain the rejected particles.
A fleece is usually made of several layers of different fineness. On the pictures above you can see something like the original photos from an interior filter. With modern computer tomography one can scan namely
such a fleece, then magnify as a 3D model and produce accordingly with a 3D printer.
Thus, a fleece must stack the material filtered out as far as possible in such a way, that the flow is impeded as little as possible. Because when manufacturers demand 4 µm at 99 percent or even more today, they are
of course not prepared to accept shorter change intervals, rather the opposite.
Therefore manufacturers of fleece for filters research which stack heights of retained particles arise at which combination of different layers of fleece. One might suppose that this would perhaps determined through
lengthy attempts, but the experts insist thereon in an interview it's now rather predictable.
Water in the fuel is, for example, in diesel engines a problem. Earlier it has settled on the ground in the filter and has been displayed by control lamp and aspirated during maintenance. Today it will mixed partially so
intense with the diesel fuel by gear pumps that it can not be so easily separated.
Also a task of fleece structures. The big challenge has actually begun with the introduction of common rail. One asks now 4 µm with 99.98 percent degree of separation here. One has less fear for clogging of the blind
holes, barely visible with the eye, but for damage to the lower sealing surface of the needle (see second video below). 09/15
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