Better Farming February 2017

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Better Farming February 2017 The Business of Ontario Agriculture 77
HOW IT WORKS
for many applications where constant
or intermittent fluid flow is required
to control functions. Some of these
functions are continuously variable
transmissions (CVTs) or hydraulic
grapples used to hold tree stems being
pulled behind log skidders.
Hydraulic filter ratings
In recent years, a considerable
amount of research has been direct-
ed to a “multi-pass” test to rate
hydraulic filters. The “beta-ratio”
(ß-ratio) derived from the multi-
pass test has become one accepted
method of determining filtration
efficiency as a percentage collection
of particles in a specified micron
particle size range, e.g. 10 to 30 µm.
New filter media, usually ar-
ranged in a pleated format to enlarge
available surface area, has been
developed to increase the “dirt
retention capacity.” Note that the
fluid must always flow from the
outside of the filter to the inner core,
which is smaller in diameter. The
filter head will be marked with a
flow direction arrow or the words
“inlet” and “outlet” will appear at
each port.
The ß-ratio is a simple term that
provides the filtration efficiency of a
given filter in removing particles of a
stated micron size range. The
filtration efficiency is the ratio of the
number of particles within the
stated micron size range which enter
the filter, compared to the same size
range of particles which pass
through without being trapped by
the filter. This filtration efficiency is
reported as a percentage value. As
would be expected, the efficiency is
higher for the larger particles.
This ß-ratio permits a filtration
efficiency to be calculated for a
specific filter element. Many filter
manufacturers are now stating those
two ratings (ß-ratio and filtration
efficiency) on their filter cartridges.
For a graphic display of these
parameters please do a Google
search of “hydraulic filter beta
ratings and the multi-pass test.” If
you open one of the top search
results, figure one provides an
excellent illustration of typical filter
The filter head will be marked with a flow direction arrow or inlet and outlet will appear at each port.