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The RF pilot valve (model 160-RF) senses the pressure differential
across the specially sized orifice plate. When the pressure differential is less than the set point, the valve opens, allowing flow to meet predetermined demand.
At the desired maximum set point, the pilot reacts to small changes
in sensing pressure and controls the main valve position by
modulating the pressure above the diaphragm.
When the pressure drop across the orifice exceeds the set point, the
valve closes slightly, limiting the flow to the pre-set maximum.
The orifice is usually sized to generate a pressure differential of 3 to
5 psi (.2 to .35 bar) at the desired maximum flow. Adjusting the pilot
setting permits the maximum flow to be changed in the field above
or below the original point.
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