Samson 3760, Mounting And Operating Instructions

Page: 17 / 36

Upper range value (travel)
e.g. 1 bar (20 mA)
3. After the starting point has been ad-
justed, increase input signal.
The plug stem must stand still at an up-
per range value of exactly 1 bar
(20 mA). It must have passed through
100 % travel (observe the travel indica-
tor on the valve!). If the upper range
value does not correlate, correct it by
adjusting the SPAN adjustment screw
(8).
Turning the screw towards the fulcrum of
the lever increases the travel, whereas
turning it away reduces the travel.
Note: Make sure that the range spring (7) is
in the upright position for adjustment. If nec-
essary, hook the spring at another point on
the lever (6).
NOTICE
If you change the span, the zero point must
be readjusted as well.
4. Check upper range value again.
Readjust both values until they are cor-
rect.
4.3 Adjustment for actuator with
fail-safe action "Actuator
stem retracts"
NOTICE
For actuator version "Actuator stem re-
tracts", the diaphragm chamber must be
loaded with a pressure that is sufficient to
tightly close the valve, even when upstream
pressure of the plant prevails.
The upper range value of the reference vari-
able must be 1 bar or 20 mA (direct direc-
tion of action >>) and the lower input range
value must be 0.2 bar or 4 mA (reverse di-
rection of action <>).
The required signal pressure is roughly cal-
culated in the same way as the required
supply pressure according to the equation in
section 3.1.2 on page 13.
Starting point (zero)
e.g. 1 bar (20 mA)
1. Adjust input signal to 1 bar (20 mA) us-
ing the remote adjuster (ammeter).
2. Turn ZERO adjustment screw (5) until
the plug stem just starts to move from its
initial position.
3. Increase input signal and slowly reduce
it to 1 bar (20 mA). Check if the plug
stem begins to move at exactly 1 bar
(20 mA).
4. Correct any deviations using the ZERO
adjustment screw (5).
EB 8385 EN
17
Operation – Adjustment