Emerson Daniel 700 Series

Technical Guide
DAN-LIQ-TG-44-rev0813
November 2013
21
X
Z
Y
X
Z
Y
OPEN - CONTROLLED POSITION - The pilot is partially open. Inlet pressure (P1) 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 (P1) pressure
equal to the pilot setting (Plus or minus 2 psi).
FULL OPEN - NO CONTROL - The pilot is full open. Inlet pressure (P1) is greater than the pilot
setting. Y-port (P3) is open to Z-port (P2). The valve is floating in the stream and no flow control
is required.
P1
P3
P2
Figure 4-10
= Inlet Pressure
= Outlet Pressure
= Controlled Pressure
= Pilot Spring Pressure
P1
P3
P2
Figure 4-11
= Inlet Pressure
= Outlet Pressure
= Pilot Spring Pressure
Sensing Chamber Line
Sensing Chamber Line
Needle Valve/Strainer
(Closing/Sensitivity Control)
Back Pressure Pilot (N.C.)
Needle Valve/Strainer
(Closing/Sensitivity Control)
Back Pressure Pilot (N.C.)