Samson 3767, Translation Of Original Instructions

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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.