Samson 3767 - Settings for Actuator with Actuator Stem Retracts Fail-Safe Action

40 EB8355-2EN
Operation
5.1.2 Settingsforactuator
with“actuatorstemex-
tends”fail-safeaction
Startingpoint(e.g.4mA)
1. Set the input signal at the ammeter to
4.5mA
2. Turnthezeroadjuster(6.2)untilthe
valve just starts to move from its initial
position.
3. Reducetheinputsignalto0mAand
slowly increase it again. Check whether
the valve starts to move at exactly
4.5mA.Correctanydeviationatthe
zeroadjuster(6.2).
Upperrangevalue(span)e.g.20mA
1. Oncethestartingpointhasbeenset,
increase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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
increase it again.
Check the starting point and the upper
range value. Repeat the correction pro-
cedureuntilbothvaluesarecorrect.
NOTICE
When setting the zero adjuster (6.2),
check whether the actuator is relieved
of pressure.
When the input signal is 4mA and
the operating direction >>, or the in-
put signal is 20mA and the operat-
ing direction <>, the pressure gauge
must indicate 0bar.
Correct zero accordingly.
5.1.3Settingsforactuatorwith
“actuatorstemretracts”
fail-safeaction
NOTICE
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 pres-
sure in the plant. This applies to an
upper range value of the reference
variable (20mA) with operating di-
rection >> as well as a lower range
value of the reference variable
(4mA) 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.20mA)
1. Set the input signal at the ammeter to
20mA