EB 8395 EN
17
Mounting and start-up
FA: actuator stem extends
(air to open/
ATO)
Fail-close (for globe and angle valves):
Required supply pressure = Upper bench
range value + 0.4 bar, minimum 1.4 bar.
FE: actuator stem retracts
(Air to close/ATC)
Fail-open (for globe and angle valves):
For tight-closing valves, the maximum signal
pressure pst
max
is roughly estimated as fol-
lows:
pst
max
=
F +
d² · π · ∆p
[bar]
4 · A
d
=
Seat diameter [cm]
∆p =
Differential pressure across the
valve [bar]
A
= Actuator area [cm²]
F
= Upper bench range value [bar]
If there are no specifications, calculate as
follows:
Recommended supply pressure =
Upper bench range value + 1 bar
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.
Note
Summary of Contents for 3724
Page 39: ...EB 8395 EN 39...