Page 24 - Parker - The Handbook of Hydraulic Filtration
P. 24
Filter Element Life
Filtration Fact Contaminant Loading element accounts for why some
Contaminant loading in a filter ele-
As an element loads with ment is simply the process of blocking elements last longer than others.
the pores throughout the element. As
contamination, the For a given filter media thickness and
the filter element becomes blocked
differential pressure will with contaminant particles, there are filtration rating, there are fewer pores
with cellulose media than fiberglass
increase over time; slowly fewer pores for fluid flow, and the pres-
media. Accordingly, the contaminant
sure required to maintain flow through
at first, then very quickly loading process would block the pores
the media increases. Initially, the dif-
as the element nears it’s ferential pressure across the element of the cellulose media element quicker
then the identical fiberglass media
maximum life. increases very slowly because there is
element.
an abundance of media pores for the
fluid to pass through, and the pore The multilayer fiberglass media
blocking process has little effect on the element is relatively unaffected by
overall pressure loss. However, a point contaminant loading for a longer time.
is reached at which successive block- The element selectively captures the
ing of media pores significantly various size particles, as the fluid pass-
reduces the number of available pores es through the element. The very small
for flow through the element. pores in the media are not blocked by
At this point the differential pressure large particles. These downstream
across the element rises exponentially. small pores remain available for the
The quantity, size, shape and arrange- large quantity of very small particles
ment of the pores throughout the present in the fluid.
Element Contamination Loading Curve
Differential Pressure
Incremental
Life
Time
22
