Differential Pressure Gages (Figure 2-15)
There are two needles and two dials on each gage. They are used to read the inlet and outlet pressure on the media filter
and cartridge filter.
The outer dial (1) indicates the actual pressure each filter is working at. The inner dial (2) indicates the difference (or
differential pressure) from the inlet to the outlet of each filter.
The black needle (3) shows the pressure going into the filer and the red needle (4) shows the pressure after the filter.
Both pressures are read on the outer dial (1).
The further apart the red and black needles are, the dirtier the filters.
There are two ways to obtain the differential pressure; subtract the red needle pressure from the black needle pressure
(as read on the outer dial) or read the inner dial differential pressure under the black needle. Either way will allow the
correct differential pressure to be obtained.
Figure 2-15. Differential Pressure Gages
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