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Purpose
of Indicators
Clogging
indicators are warning devices that signal visually and/or
electrically that the filter element is filled with contaminants
and should be changed or cleaned. These devices activate
(trip) when the flow of fluid causes a pressure drop across
the filter that exceeds the indicator settings. In filters
that incorporate bypass valves, contaminated fluid will
bypass the element if the operator does not respond to
the indicator warning signal within a reasonable time.
In non-bypass filters, if the indicator warning is not
heeded, the pressure across the filter will build up to
the point where system performance is degraded or the
element fails.
The
indicator is set to trip well before the element becomes
fully clogged, thereby giving the operator sufficient
time to take corrective action. The indicator warning
may be a visual signal at the filter site (pop-up button,
light, etc.); or, some form of signal at a remote location
(trouble light, sound alarm, etc.). In some critical applications,
where contamination is intolerable, the signal from the
indicator may be used to shut down the system so as to
compel immediate servicing.
Some
users install filters without indicators, preferring instead
to change and/or clean elements according to a fixed schedule
- or based on number of hours of operation. There is some
risk in utilizing this approach. It may be difficult to
establish a reliable schedule for installing new elements
because the rate of dirt ingression is not known, and,
in fact, may vary from time-to-time and from machine-to-machine.
Use of a clogging indicator has two main benefits: first,
it eliminates the need to guess when the element will
clog; second, it avoids the unnecessary cost of replacing
elements too soon.
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