Emerson Daniel 700 Series Technical Manual page 25

Technical Guide
DAN-LIQ-TG-44-rev0813
November 2013
OPEN - CONTROLLED POSITION - The pilot is partially open. Differential pressure (P1 minus P4)
has slightly exceeded the pilot spring setting. Z-port (P2) is being opened by the throttling of
the pilot, reducing the pressure on Y-port (P3). The decreasing pressure at Y-port (P3) plus the
main valve spring force establishes a position of the valve piston such that is balances the pump
differential pressure (P1 minus P4) equal to the pilot setting (Plus or minus 2 psid).
= Inlet Pressure
= Outlet Pressure
= Controlled Pressure
= Pilot Spring Force
FULL OPEN - NO CONTROL - The pilot is full open. Differential pressure (P1 minus P4) has
exceeded the pilot spring setting. Y-port (P3) is open to Z-port (P2). The valve is floating the
stream and is not required to control.
= Inlet Pressure
= Outlet Pressure
= Pilot Spring Force
P1
P4
Figure 4-13
P1
P4
Figure 4-14
23
Y
X
Y
X
Y
P3
X
Y
X
Y
X
Y
P3
X
Z
Z
Z
P2
Z
Z
Z
P2