Page 28 - Parker - The Handbook of Hydraulic Filtration
P. 28
Filter Housing Selection
Filtration Fact Element Condition Housing And
Element Sizing
Indicators
Always consider low tem- The element condition indicator The filter housing size should be large
signals when the element should be enough to achieve at least a 2:1 ratio
perature conditions when
cleaned or replaced. The indicator usu- between the bypass valve setting and
sizing filters. Viscosity ally has calibration marks which also the pressure differential of the filter
increases in the fluid may indicates if the filter bypass valve has with a clean element installed. It is
opened. The indicator may be mechan- preferable that this ratio be 3:1 or
cause a considerable
ically linked to the bypass valve, or it even higher for longer element life.
increase in pressure differ- may be an entirely independent differ-
ential through the filter ential pressure sensing device. For example, the graph on the next
Indicators may give visual, electrical or page illustrates the type of catalog
assembly.
both types of signals. Generally, indica- flow/pressure differential curves which
tors are set to trip anywhere from are used to size the filter housing. As
Filtration Fact 5%-25% before the bypass valve opens. can be seen, the specifier needs to
know the operating viscosity of the
Pressure differential fluid, and the maximum flow rate
(instead of an average) to make sure
in a filter assembly
that the filter does not spend a high
depends on: portion of time in bypass due to flow
1. Housing and surges. This is particularly important
in return line filters, where flow multi-
element size
plication from cylinders may increase
2. Media grade the return flow compared to the pump
3. Fluid viscosity flow rate.
4. Flow rate
Filtration Fact Filter Element Sizing
It is recommended to use
an element condition
indicator with any filter, Filter
Bypass
Differential Pressure Ratio
especially those that Cracking
do not incorporate a LIFE Pressure 3:1 Optimum
bypass valve.
Clean
Element
P
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