Connections; Pneumatic Connections; Supply Pressure - Samson 3725 Mounting And Operating Instructions

Connections

5 Connections

5.1 Pneumatic connections

The pneumatic connections are optionally
designed as a bore with ¼ NPT or G ¼
thread. The customary fittings for metal and
copper pipes or plastic hoses can be used.
Points that apply concerning the pneumatic
connections:
Î Only screw the screw fittings into the
connecting plate, pressure gauge mount-
ing block or connection block from the
accessories. Do not screw them directly
into the positioner housing.
Î Keep the length of the line as short as
possible to avoid delays in control signal
transmission.
NOTICE
Dirty supply air will cause the posi-
tioner to malfunction!
Only use supply air that is dry and
free of oil and dust.
Blow through all air pipes and hoses
thoroughly before connecting them.
The signal pressure connection is fixed when
the positioner is directly attached to the
Type 3277 Actuator.
For attachment according to IEC 60534-6
(NAMUR), the signal pressure can be routed
to either the top or bottom diaphragm cham-
ber of the actuator, depending on the actua-
tor's fail-safe action "actuator stem extends"
or "actuator stem retracts".
34
For rotary actuators, the manufacturer's
specifications for connection apply.
Tip:
To monitor the supply air (supply)
and signal pressure (output), we rec-
ommend mounting pressure gauges
(see accessories in section 4.7).
5.1.1

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
spring range or signal pressure range. The
operating direction is marked FA or FE, or by
a symbol.
Fail-close or ATO (air to open):
Actuator stem extends
Fail-open or ATC (air to close):
Actuator stem retracts
Supply pressure for fail-close valves (for
globe and angle valves):
Î Required supply pressure = Upper bench
range value + 0.2 bar, minimum 1.4 bar.
EB 8394 EN