Page 112 - ingenioren

Technical Reference

Liquid Filtration Pressure Drop named Synteq™/ Synteq fibers offer the least amount
of resistance to fluid passing through the media.
The difference between the inlet pressure and the Consistency of fiber shape allows the maximum
outlet pressure is called pressure drop or differential amount of contaminant catching surface area and
pressure. It’s symbolized by ∆P. ∆P is an irrecoverable specific pore size control.
loss of total pressure caused by the filter, and is
mostly due to frictional drag on the fibers in the The result is media with predictable filtration
media. efficiencies at removing specified contaminants (i.g.,
4 μm) and maximum dirt holding capacity. Natural
∆P may increase as the particulate rating or efficiency cellulose fibers are larger than synthetic fibers and
of the filter gets better. ∆P also increases as the filter jagged in shape, so controlling size of the pores in the
is being loaded with contaminant. media mat is difficult and there is less open volume.
In most applications this
results in higher ∆P as
Major Factors Contribute to Pressure Drop compared to synthetic
filters. Higher beta ratings
1. Filter Media mean there are smaller
pores in the media; smaller
Media is, of
course, the main media pores cause more
factor influencing flow resistance, in turn
pressure drop; causing higher pressure
ENGINE LIQUID FILTRATION TECHNICAL REFERENCE
indeed, it causes drop.
pressure drop. 2. Dirt,
That’s why having a Contaminant
low-friction, high-
flowing media is As dirt gets caught in the
so important. The media, it eventually begins
natural cellulose or to build up and fill the pore openings.
paper fibers (shown Cellulose filter media photo from As the pore openings shrink, the differential pressure
at left) typically scanning electron microscope (pressure drop) increases. This is called restriction.
used in filtration are magnified hundreds This photo from our scanning electron microscope
large, rough, and as of times. shows actual dirt particles building up in the media
irregular as nature pores.
made them.
Typically there is a restriction limit for the system the
Donaldson filter has been applied to. The amount of restriction
developed a filter can have before the system performance
synthetic media becomes affected is called the filter terminal pressure
with smooth, drop. This will usually be the point at which the filter
rounded fibers, capacity will be stated.
consistently 3. Flow
shaped so that
we can control Higher flows create higher pressure drop. With fast
the fiber size moving fluid, there will be more friction causing
and distribution higher pressure drop across the media.
pattern throughout
the media mat,
and still allow Donaldson Synteq™ synthetic filter
media (left) is magnified hundreds of
the smoothest, times under the scanning electron
least inhibited microscope. The smooth rounded
fluid flow. Our fibers provide low resistance to fluid
flow.
synthetic media is

110 • Engine Liquid Filtration www.donaldson.com