Brochure

4
Pressure Reducing Valve
When the downstream pressure is greater than
the set point of the pilot, the pilot is closed, result-
ing in equal pressure above and below the main
diaphragm. With a balancing diaphragm area
slightly larger than the seat area, the resulting
closing force, along with the force of the main
spring, forces the plug against the seat.
With an increase in demand, the outlet pressure
will begin to drop and decrease the pressure
above the main diaphragm. The drop of the outlet
pressure below the pilot set point will cause the
pilot to open. As the pilot opens, pressure increas-
es underneath the main diaphragm faster than
pressure can bleed through the internal restrictor.
The imbalance in pressure on the main diaphragm
overcomes the spring force and the additional
closing force from the balancing diaphragm,
causing the plug to rise off the seat and satisfy
the flow demand.
Once the flow demand is satisfied and the down-
stream pressure begins to increase, the pressure
above the main diaphragm and in the pilot sense
cavity rises.
This causes the pilot to close. The pressure below
the main diaphragm bleeds through the inter-
nal restrictor until pressure equalizes above and
below the main diaphragm. The forces of the main
spring and the over-sized balancing diaphragm
then close the plug on the seat.
Back Pressure Valve
In a back pressure relief application (BPV) the valve
functions to maintain upstream pressure at the
pilot set point. The sense line for the control pilot is
located upstream of the regulator. The extra sense
port on the actuator is plugged for BPV pilot
configuration. The action of the pilot is the reverse
of a pressure reducing pilot, such that the pilot
opens when the upstream pressure increases
above its set point. The pilot will close when the
upstream pressure is less than its set point.
Designed for bubble tight shut-off at all
pressures and full capacity at very low
differential pressures.
Regulator Sense Line
Balancing Diaphragm
Internal Restrictor
PRV Pilot Sense
Pilot Loading
Pilot Supply
Inlet Pressure
Loading Pressure Outlet Pressure
Plug
for BPV
BPV Pilot Sense