Data Sheet

Bulletin 71.2:92C
5
Figure 3. Type 92C Pressure-Loaded Control Valve Operational Schematic


36A1546-B
A2946
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






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




Refer to the schematic in Figure 2. Pilot supply
pressure is piped from the inlet side of the main valve
to the pilot inlet connection. Downstream pressure
registers under the main valve diaphragm through
the pitot tube under the pilot diaphragm through the
downstream control line.
When downstream pressure decreases to a value
below the setting of the pilot regulator spring, the pilot
spring forces the pilot valve plug open, increasing
the loading pressure on the top of the main valve
diaphragm. The increased loading pressure on top of
the main valve diaphragm and decreased downstream
pressure under the main valve diaphragm force the
main valve diaphragm and stem downward. This
opens the main valve plug, and increases ow to
the downstream system thus restoring downstream
pressure to the setting of the pilot regulator spring.
When downstream pressure increases, it registers under
the pilot diaphragm and overcomes the force of the pilot
spring. This allows the pilot valve spring to close the pilot
valve plug and causes excess loading pressure to bleed
to the downstream system through the pilot bleed hole. At
the same time, increased downstream pressure registers
under the main valve diaphragm. The decreased
loading pressure on top of the main valve diaphragm and
increased downstream pressure under the main valve
diaphragm force the main valve diaphragm upward. This
allows the main valve plug spring close to the main valve
plug, reducing ow to the downstream system.