Signal Pressure Gauges; Supply Pressure; Signal Pressure (Output) - Samson 3731-5 Mounting And Operating Instructions

Mounting and start-up
Type 3277 Actuator
Î The signal pressure connection is fixed.
Attachment according to IEC 60534-6
(NAMUR)
Î For "actuator stem retracts" fail-safe ac-
tion: connect the signal pressure to the
connection on the bottom of the actuator.
Î For "actuator stem extends" fail-safe ac-
tion: connect the signal pressure to the
connection on top of the actuator.
Attachment to rotary actuators
Î For rotary actuators, the manufacturer's
specifications for connection apply.

5.10.2 Signal pressure gauges

Tip
To monitor the supply air and signal pres-
sure, we recommend mounting pressure
gauges (see accessories in section 3.3).
Mounting the pressure gauges:
Î See sections 5.5 and Fig. 7

5.10.3 Supply pressure

The maximum input pressure (supply pres-
sure) is:
− Maximum 7 bar for Types 3731-521/-
527
− Maximum 6 bar for Type 3731-523
The required supply air pressure depends on
the bench range and the actuator's direction
of action (fail-safe action).
44
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

5.10.4 Signal pressure (output)

The signal pressure at the output (38) of the
positioner can be restricted to 1.4 bar,
2.4 bar or 3.7 bar in Code 16.
The limitation is not activated [No] by de-
fault.
[bar]
EB 8387-5 EN