Samson 3730-0 - Signal Pressure Connection; Signal Pressure Gauges; Supply Pressure; Signal Pressure (Output)

EB 8384-0 EN 49
Mounting and start-up
5.11.1 Signal pressure connec-
tion
The signal pressure connection depends on
how the positioner is mounted onto the actu-
ator:
Type 3277 Actuator
Î Thesignalpressureconnectionisxed.
Attachment according to IEC 60534-6
(NAMUR)
Î For "actuator stem retracts" fail-safe ac-
tion: connect the signal pressure to the
connection on top of the actuator.
Î For "actuator stem extends" fail-safe ac-
tion: connect the signal pressure to the
connection on the bottom of the actuator.
5.11.2 Signal pressure gauges
To monitor the supply air and signal pres-
sure, we recommend mounting pressure
gauges.
Mounting the pressure gauges:
Î Seesection5.4andsectionFig.8
5.11.3 Supply pressure
The required supply air pressure depends on
the bench range and the actuator's direction
of action (fail-safe action).
The bench range is written on the nameplate
either as the bench range or signal pressure
range depending on the actuator. The direc-
tion of action is marked FA or FE or by a
symbol.
Actuator stem extends FA (AIR TO OPEN)
Fail-close (for globe and angle valves):
Î Requiredsupplypressure=Upperbench
rangevalue+0.2bar,atleast1.4bar.
Actuator stem retracts FE (AIR TO CLOSE)
Fail-open (for globe and angle valves):
For tight-closing valves, the maximum signal
pressure pst
max
is roughly estimated as fol-
lows:
pst
max
= F +
d²·π·∆p
[bar]
4 · A
d = Seatdiameter[cm]
∆p = Differential pressure across the
valve[bar]
A = Actuatorarea[cm²]
F = Upper bench range value of the
actuator[bar]
If there are no specications, calculate as
follows:
Î Requiredsupplypressure=Upperbench
rangevalue+1bar
5.11.4 Signal pressure (output)
The signal pressure at the output (38) of the
positioner can be restricted to approx.
2.4barattheDIPswitchS5.
Tip