Connections; Pneumatic Connections; Signal Pressure Gauges; Supply Pressure - Samson 3730-3 Mounting And Operating Instructions

Connections

3 Connections
3.1

Pneumatic connections

Caution!
The threads in the positioner housing are not
designed for direct air connection!
The screw glands must be screwed into the
connecting plate, the pressure gauge mount-
ing block or the connection block from the
accessories. The air connections are option-
ally 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.
Note!
The supply air must be dry and free from oil
and dust. The maintenance instructions for
upstream pressure reducing stations must be
observed.
Blow through all air tubes and hoses thor-
oughly prior to connecting them.
If the positioner is attached directly to the
Type 3277 Actuator, the connection of the
positioner's output pressure to the actuator
is fixed. For attachment according to
IEC 60534-6 (NAMUR), the signal pressure
can be routed to either the top or bottom di-
aphragm chamber of the actuator, depend-
ing on the actuator's fail-safe action "Actua-
tor stem extends" or "Actuator stem re-
tracts".
For rotary actuators, the manufacturer's
specifications for connection apply.
34
EB 8384-3 EN

3.1.1 Signal pressure gauges

To monitor the supply air (Supply) and sig-
nal pressure (Output), we recommend that
pressure gauges be attached (see accesso-
ries in Tables 1 to 5).

3.1.2 Supply pressure

The required supply air pressure depends
on the bench range and the actuator's oper-
ating direction (fail-safe action).
The bench range is registered on the name-
plate either as spring range or signal pres-
sure range depending on the actuator. die
The direction of action is marked FA or FE,
or by a symbol.
Actuator stem extends FA (Air to open
ATO)
Fail-safe position "Valve Closed"
(for globe and angle valves):
Required supply pressure = Upper bench
range value + 0.2 bar, minimum 1.4 bar.
Actuator stem retracts FE (Air to close ATC)
Fail-safe position "Valve Open"
(for globe and angle valves):
For tight-closing valves, the maximum signal
pressure pst is roughly estimated as fol-
max
lows:
⋅ ⋅ π ∆
2
d
pst = F +
max
⋅
4 A
p