Mooney Flowgrid, Installation, Operation & Maintenance Manual, Page: 4 / 16

4 | Dresser
Figure 4. Pressure Reducing Confi guration Fully Closed
Principal of Operation
Pressure Reducing Application (PRV)
PILOT LOADING
CONNECTION
PILOT SUPPLY
INLET
OUTLET
PILOT OUTLET
CONNECTION
RESTRICTOR
PILOT SENSE
CONNECTION
PILOT SUPPLY
PILOT LOADING
CONNECTION
PILOT SENSE
CONNECTION
INLET OUTLET
PILOT OUTLET
CONNECTION
RESTRICTOR
Figure 5. Pressure Reducing Confi guration Partially Open
At no flow, when the outlet pressure is greater than the set
point of the pilot regulator, the pilot is closed and full inlet
pressure loads the spring case through the pilot loading
connection. In this condition the diaphragm is closed tightly
against the throttle plate. The pressure differential across the
outlet half of the diaphragm adds to the spring force in closing
the Flowgrid
®
valve (Refer to Figure 4).
As demand for flow occurs in the downstream system the
outlet pressure drops, causing the pilot regulator to open and
start bleeding pressure out of the spring case faster than it
can enter through the restrictor. Reducing the pressure above
the diaphragm allows the inlet pressure to progressively lift
the diaphragm off the throttle plate, opening the valve and
satisfying the demand for flow in the downstream system.
(Refer to Figure 5).
PILOT LOADING
CONNECTION
PILOT SUPPLY
INLET OUTLET
PILOT OUTLET
CONNECTION
RESTRICTOR
PILOT SENSE
CONNECTION
Fig 7. Back Pressure Confi guration Partially Open
Fig 6. Back Pressure Confi guration Fully Closed
PILOT LOADING
CONNECTION
PILOT SUPPLY
INLET OUTLET
PILOT OUTLET
CONNECTION
RESTRICTOR
PILOT SENSE
CONNECTION
When demand for flow ceases or is reduced, the downstream
pressure increases causing the pilot regulator to close. Inlet
pressure continues to pass through the restrictor until the
control pressure equals the inlet pressure. The spring force,
plus the pressure differential across the outlet half of the
diaphragm closes the diaphragm against the throttle plate,
shutting off the flow (Refer to Figure 4).
Adjustment of the restrictor affects the response rate, stability,
and sensitivity of the regulator. Smaller restrictor openings
result in higher gain (sensitivity) and slower closing speeds.
Larger openings result in lower gain (greater proportional
band), greater stability and faster closing speeds.