Signal Pressure Gauges; Supply Pressure - Samson 3730 Series Mounting And Operating Instructions

Mounting and start-up
The pneumatic connections in the connecting
plate, pressure gauge mounting block and
connection block are optionally designed as
a bore with ¼ NPT or G ¼ thread. Custom-
ary fittings 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 fixed.
− 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
specifications for connection apply.

5.15.2 Signal pressure gauges

Tip
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
84

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 is roughly estimated as fol-
max
lows:
d² · π · ∆p
pst = F +
max
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 specifications, calculate as
follows:
Î Required supply pressure = Upper bench
range value + 1 bar
[bar]
EB 8384-5 EN