Samson 3767 - Adjusting the Positioner

EB 8355-2 EN 5-19
Installation
Actuator stem extends (FA): fail-close
(for globe and angle valves)
Required supply pressure =
Upperbenchrangevalue+0.2bar,
atleast1.4bar.
Actuator stem retracts (FE): fail-open
(for globe and angle valves)
For tight-closing valves, the maximum signal
pressure pstmax 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 of the
actuator [bar]
If there are no specications, calculate as
follows:
Required supply pressure =
Upperbenchrangevalue+1bar
Pressure regulator
After tilting the cover plate back, the pres-
sure regulator (9) can be continuously ad-
justed. When the adjuster is turned counter-
clockwise as far as it will go, signal pres-
suresforspringrangesupto2.5barare
controlled. When the adjuster is turned
clockwise all the way, signal pressures for
springrangesupto6.0bararecontrolled.
If the signal pressure must not exceed a cer-
tain value, this limit can be adjusted using a
pressure gauge (accessories).
5.5 Adjusting the positioner
Intrinsic safety rendered ineffective in in-
trinsically safe devices.
Î Only connect intrinsically safe devices in-
tended for use in intrinsically safe circuits
to certied intrinsically safe input-con-
nected units.
Î Do not place intrinsically safe devices
back into operation that were connected
to intrinsically safe input-connected units
without certication.
Î Do not exceed the maximum permissible
electric values specied in the EC type
examination certicates when intercon-
necting intrinsically safe electrical equip-
ment (U
i
or U
0
, l
i
or I
0
, P
i
or P
0
, C
i
or C
0
and L
i
or L
0
).
Starting point and set point
When adjusting the positioner directly at the
control valve, the travel (opening angle) must
be adapted to the set point.
− With a set point, for example 4 to
20mA,thevalvemustmovethroughits
entiretravelrangefrom0to100%
(Fig.5-11, top).
− On mounting the positioner on rotary ac-
tuators, an opening angle, for example 0
to70°mustbeassignedtothesetpoint.
− The starting point is based on the
CLOSED position of the valve. Depend-
ing on the control valve version ("actua-
tor stem extends" or "actuator stem re-
tracts") and the operating direction of the
WARNING
!