Samson 3766 - Settings for Actuator with Actuator Stem Retracts Fail-Safe Action

40 EB 8355-1 EN
Operation
If the upper range value is incorrect, turn the
span adjuster (travel). Four turns correspond
toatravelchangeof10%instandardoper-
ation. In split-range operation, 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 the upper
range value.
Repeat the correction procedure until
both values are correct.
5.1.3 Settings for actuator with
“actuator 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. This applies to an upper range val-
ue of the reference variable (1bar) with op-
erating direction >> as well as a lower range
value of the reference variable (0.2bar) with
operating direction <>.
The required signal pressure is either indi-
cated on the positioner label or the required
supply pressure can be roughly calculated as
describedinsection4.1.2.
Starting point (e.g. 1bar)
1. Adjusttheinputsignalto1baratthe
pressure adjuster.
2. Turnthezeroadjuster(6.2)untilthe
valve just starts to move from its initial
position.
3. Increase the input signal and slowly re-
duceitagainto1bar.Checkwhether
the valve starts to move at exactly
0.1bar.
4. Correct any deviation at the zero adjust-
er(6.2).Turningtheadjustercounter-
clockwise causes the valve to move from
itsendpositionearlier;turningclockwise
causes the valve to move from its end po-
sition later.
Upper range value (span) e.g. 0.2bar
1. Once the starting point has been set, in-
creasetheinputsignalto0.2baratthe
pressure adjuster.
Atexactly0.2bar,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1baragain.
NOTICE
!