Differential Pressure Indicators
The extent to which a filter element is loaded can
be determined by measuring the drop in hydraulic
pressure across the element under rated flow
conditions.
This drop or “differential pressure”
provides a convenient means of monitoring the
condition of installed filter elements, and is the
operating principle used in the differential-pressure or
loaded-filter indicators found on many filter
assemblies. Differential pressure indicating devices
have many configurations, including electrical
switches, continuous-reading visual indicators
(gauges), and visual indicators with memory. Visual
indicators with memory usually take the form of
magnetic or mechanically latched buttons or pins that
extend when the differential pressure exceeds that
allowed for a serviceable element. See figure 7-33.
When this increased pressure reaches a specific value,
inlet pressure forces the spring-loaded magnetic
Figure 7-33.—Hydraulic filter assembly incorporating differential pressure indicator.
7-34
