Supply Pressure - Samson 3725 Mounting And Operating Instructions

Mounting and start-up
Attachment according to IEC 60534-6
(NAMUR)
Î For attachment according to IEC 60534-
6 (NAMUR), the signal pressure can be
routed to either the top or bottom dia-
phragm chamber of the actuator, de-
pending on the actuator's fail-safe action
"actuator stem extends" or "actuator
stem retracts".
Rotary actuators (heavy-duty version)
Î For rotary actuators, the manufacturer's
specifications for connection apply.
Tip
To monitor the supply air and signal pres-
sure, we recommend mounting pressure
gauges (see accessories in section Table 6).
Mounting the pressure gauges:
Î See sections 5.3 and Fig. 10
5.7.2

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
44
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.
Supply pressure for fail-open valves (for
globe and angle valves):
Î For tight-closing valves, the maximum
signal pressure pst
ed as follows:
pst = F +
max
d = Seat diameter [cm]
Differential pressure across the
∆p =
valve [bar]
A = Actuator area [cm²]
F = Upper bench range value [bar]
If there are no specifications, calculate as
follows:
Î Required supply pressure = Upper bench
range value + 1 bar
Note
The signal pressure at the output (38) of the
positioner can be restricted to approx.
2.3 bar by setting P9 parameter code to
ON.
is roughly estimat-
max
d² · π · ∆p
[bar]
4 · A
EB 8394 EN