Samson 3767 - Page 46

5-22 EB 8355-2 EN
Installation
Upper range value (span) e.g. 20 mA
1. Once the starting point has been set, in-
creasetheinputsignalto20mAatthe
ammeter.
Atexactly20mA,theplugstemmust
standstill,havingmovedthrough100%
travel (watch the travel indicator at the
valve).
If the upper range value is incorrect, turn
the span adjuster (travel). Four turns cor-
respondtoatravelchangeof10%in
standard operation. In split-range opera-
tion, this value is reduced by half.
Turn the adjuster clockwise to reduce the
travel and counterclockwise to increase
it.
2. After the correction has been completed,
reduce the input signal and slowly in-
crease it again. Check the starting point
and upper range value.
Repeat the correction procedure until
both values are correct.
b) Actuator with "stem retracts"
fail-safe action
When using an actuator with fail-safe action
"actuator stem retracts", the diaphragm
chambermustbepressurizedwithasignal
pressure that is high enough to tightly close
the valve against the upstream pressure in
the plant.
Î Operatingdirection<<:Upperrange
valueofsetpoint20mA
Î Operatingdirection<>:Lowerrangeval-
ueofsetpoint4mA
The required signal pressure is either indicat-
ed on the positioner label or it can be rough-
lycalculatedasdescribedinsection5.4.2.
Starting point, e.g. 20mA
1. Turnthezeroadjuster(6.2inFig.5-3)
until the valve just starts to move from its
initial position.
2. Increase the input signal and slowly re-
duceitagainto20mA.Checkwhether
the valve starts to move at exactly
20mA.
3. Correctanydeviationatthezeroadjust-
er (6.2 in Fig.5-3). Turning the adjuster
counterclockwise causes the valve to
move from its end position earlier; turn-
ing clockwise causes the valve to move
from its end position later.
Upper range value (span), e.g. 4 mA
1. Once the starting point has been set, ad-
justtheinputsignalto4mAattheam-
meter.
Atexactly4mA,theplugstemmust
standstill,havingmovedthrough100%
travel (watch the travel indicator at the
valve).
2. If the upper range value is incorrect, turn
the span adjuster (travel). Four turns cor-
respondtoatravelchangeof10%in
standard operation. In split-range opera-
tion, this value is reduced by half.
Turn the adjuster clockwise to reduce the
travel and counterclockwise to increase
it.
3. After the correction has been completed,
settheinputsignalto20mAagain.