Technical Guide
DAN-LIQ-TG-44-rev0813
November 2013
X
Z
Y
X
Z
Y
19
= Inlet Pressure
= Outlet Pressure
= Spring Force
= Pilot Spring Pressure
OPEN - CONTROLLED POSITION - The pilot is partially open. Outlet pressure has slightly
exceeded the pilot spring. 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 so it balances outlet pressure equal to the pilot
setting (plus or minus 2 psi).
CLOSED POSITION - The pilot is closed. Outlet pressure (P2) exceeded the pilot spring setting,
indicating the main line downstream (P2) is closed. Y-port (P3) to Z-port (P2) is closed. X-port (P1)
and Y-port (P3) pressures become balanced. The main valve spring, being the differential force,
closes the piston and keeps it seated.
P1
P3
P2
Figure 4-7
P1
P3
P2
Figure 4-8
= Inlet Pressure
= Outlet Pressure
= Pilot Spring Pressure
Sensing Chamber Line
Pressure Reducing Pilot (N.O.)
Needle Valve/Strainer
(Closing/Sensitivity Control)
Sensing Chamber Line
Pressure Reducing Pilot (N.O.)
Needle Valve/Strainer
(Closing/Sensitivity Control)
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