Emerson Daniel 700 Series

Technical Guide
DAN-LIQ-TG-44-rev0813
November 2013
27
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 it balances inlet pressure
(P1) equal to the pilot setting plus vapor pressure (P4) (Plus or minus 2 psid).
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
= Controlled Pressure
= Pilot Spring Force plus P4
= Product Pressure
X
Z
Y
Z
Y
X
X
Z
Y
P1
P3
P2
Figure 4-18
P4
Flow Meter
X
Z
Y
Z
Y
X
X
Z
Y
= Inlet Pressure
= Outlet Pressure
= Pilot Spring Force plus P4
= Product Pressure
P3
P2
Figure 4-19
P4
Flow Meter
P1
Vapor Pressure
Liquid
Sense Line (LO)
Needle Valve/Strainer
(Closing/Sensitivity Control)
Differential
Pilot (N.C.)
Vapor Pressure
Liquid
Sense Line (LO)
Needle Valve/Strainer
(Closing/Sensitivity Control)
Differential
Pilot (N.C.)