Samson 3725 series, Mounting And Operating Instructions

Page: 35 / 68

EB 8394 EN 35
Connections
Supply pressure for fail-open valves (for
globe and angle valves):
Î
For tight-closing valves, the maximum
signal pressure pst
max
is roughly estimat-
ed as follows:
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:
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 pa -
rameter code to ON.
5.2 Electrical connections
DANGER!
Risk of electric shock and/or the for-
mation of an explosive atmosphere.
−
For electrical installation in hazard-
ous areas, observe the relevant
electrotechnical regulations and
valid test certification that apply in
the country of use. The following
regulations apply: EN 60079-14:
Explosive atmospheres – Part 14
(VDE 0165-1):
Explosive atmo-
spheres – Electrical installations
design, selection and erection .
−
Avoid electrostatic charging of the
plastic housing when mounting and
servicing the positioner in hazard-
ous areas.
NOTICE
−
Do not undo the enameled screws
in or on the housing.
− When interconnecting intrinsically
safe device versions with other cer-
tified intrinsically safe equipment,
observe the maximum permissible
values U
i
, I
i
, P
i
, L
i
and C
i
specified
in the EC-type examination certifi -
cate.
