Samson 3730-3 - Signal Pressure Gauges; Supply Pressure

82 EB 8384-3 EN
Mounting and start-up
aborewith¼NPTorG¼thread.Custom-
aryttingsformetalorcoppertubingor
plastic hoses can be used.
Signal pressure connection
The signal pressure connection depends on
how the positioner is mounted onto the actu-
ator:
− Type 3277 Actuator
Thesignalpressureconnectionisxed.
− Attachment according to IEC 60534-6
(NAMUR)
For "actuator stem retracts" fail-safe ac-
tion: connect the signal pressure to the
connection on top of the actuator.
For "actuator stem extends" fail-safe ac-
tion: connect the signal pressure to the
connection on the bottom of the actuator.
− Rotary actuators
For rotary actuators, the manufacturer's
specicationsforconnectionapply.
5.15.2 Signal pressure gauges
To monitor the supply air and signal pres-
sure, we recommend mounting pressure
gauges (seeaccessoriesinsection3.6).
Mounting the pressure gauges:
Î Seesection5.4andsectionFig.8
5.15.3 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 sym-
bol.
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
Tip