Increasing The Actuator Thrust; Adapting The Travel Range; Adjusting The Travel Stop - Samson 3372 Mounting And Operating Instructions

5. Screw the short nuts (A21) with shims
(A25) onto the bolts (A20). Observe
tightening torques.
6.1.2 Increasing the actuator
thrust
The thrust can only be increased in actuators
with "stem extends" direction of action. To
achieve this, the springs of the actuators can
be preloaded by up to 25 % of their travel or
bench range.
Example: Preloading is required for a bench
range of 1.5 to 2.1 bar. 25 % of this span is
0.15 bar. Therefore, the signal pressure
range is shifted by 0.15 bar to 1.65 to
2.25 bar. The new lower signal range value
is 1.65 bar and the new upper signal range
value 2.25 bar.
Î Write the new signal pressure range of
1.65 to 2.25 bar on the actuator name-
plate as the operating range with pre-
loaded springs.
6.1.3 Adapting the travel
range
In some cases, the valve and actuator have
different rated travels. Depending on the di-
rection of action, proceed as follows:
Direction of action: actuator stem extends
Always use actuators with preloaded springs
when the valve's rated travel is smaller than
the rated travel of the actuator.
EB 8313-3 EN
Example: DN 25 valve with 15 mm rated
travel and 350 cm² actuator with 30 mm rat-
ed travel; 1.5 to 2.7 bar bench range.
The signal pressure for half the actuator trav-
el (15 mm) is 2.1 bar. Adding it to the lower
signal pressure range value of 1.5 bar re-
sults in a signal pressure of 3.6 bar required
for spring compression. The new lower sig-
nal range value is 3.6 bar and the new up-
per signal range value 4.8 bar.
Î Write the new signal pressure range of
3.6 to 4.8 bar on the actuator nameplate
as the operating range with preloaded
springs.
Direction of action: actuator stem retracts
The springs of actuators with "stem retracts"
action cannot be preloaded. When a
SAMSON valve is combined with an
oversized actuator (e.g. the rated travel of
the actuator is larger than the rated travel of
the valve), only the first half of the actuator's
bench range can be used.
Example: DN 25 valve with 15 mm rated
travel and 350 cm² actuator with 30 mm rat-
ed travel; 1.5 to 2.7 bar bench range.
At half the valve travel, the operating range
is between 1.5 and 2.1 bar.

6.2 Adjusting the travel stop

See Fig. 6-2
The Type 3372 Electropneumatic Actuator
(120 cm²) can optionally be fitted with a
travel stop to limit the minimum and maxi-
mum travel. These stops can be combined.
Start-up
6-3