Figure 9-48.—Proportional-flow filter,
pressure. The pressure difference forces some of
the fluid through the element to rejoin the main
stream at the venturi. The amount of fluid filtered
is proportional to the flow velocity. Hence, the
name proportional-flow filter.
Indicating Filters
Indicating filters are designed to signal the
operator when the element needs cleaning.
There are various types of indicators, such
as color-coded, flag, pop-up, and swing arm.
Figure 9-49 shows a color-coded indicating
filter. The element is designed so it begins
to move as the pressure increases due to dirt
accumulation, One end is linked to an indicator
that shows the operator just how clean or
dirty the element is. Another feature of this
type of filter is the ease and speed with
which the element can be removed and replaced.
Most filters of this kind are designed for
inlet line installation.
Figure 9-49.—Color-coded indicating filter.
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