Technical Guide
DAN-LIQ-TG-44-rev0813
November 2013
29
X
Z
Y
Note: Minimum of 5 psid required for Control
= Inlet Pressure and Pilot Spring Force plus P1
= Outlet Pressure
= Controlled Pressure
= Product Pressure
OPEN - CONTROLLED POSITION - The pilot is partially open. Differential pressure (P4 minus P1)
has slightly exceeded the pilot spring setting. Z-port (P2) is being squeezed off by the throttling
of the pilot, placing higher pressure on Y-port (P3). The increasing pressure at Y-port (P3) plus the
main valve spring force establishes a position of the valve piston such that it balances differential
pressure (P4 minus P1) equal to the pilot setting (plus or minus 2 psid), which is proportional to
the flow rate.
P3
P2
P4
P1
Flow Meter
Figure 4-21
Sense Line (LO)
Needle Valve/Strainer
(Closing/Sensitivity Control)
Differential
Pilot (N.C.)
Sense Line (HI)
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