Increasing The Actuator Thrust; Adapting The Travel Range - Samson 3277 Mounting And Operating Instructions

5. Screw the short nuts (A21) with washers
(A25) onto the bolts (A20). Observe
tightening torques.
5.2.2 Increasing the actuator
thrust
The thrust can only be increased in actuators
with "stem extends" action. To achieve this,
the springs of the actuators can be preload-
ed by up to 25 % of their travel or bench
range.
Example: Preloading is required for a bench
range of 0.2 to 1 bar. 25 % of this span cor-
responds to 0.2 bar. Therefore, the signal
pressure range is shifted by 0.2 bar to 0.4 to
1.2 bar. The new lower signal pressure
range value is 0.4 bar and the new upper
signal pressure range value 1.2 bar.
Î Write the new signal pressure range of
0.4 to 1.2 bar on the actuator nameplate
as the operating range with preloaded
springs.
5.2.3 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 8310-5 EN
Example: DN 50 valve with 15 mm rated
travel and 750 cm² actuator with 30 mm rat-
ed travel; 0.4 to 2 bar bench range.
The signal pressure for half of the actuator
travel (15 mm) is 1.2 bar. Adding it to the
lower signal pressure range value of 0.4 bar
results in a signal pressure of 1.6 bar re-
quired for preloading the springs. The new
lower signal range value is 1.6 bar and the
new upper signal range value 2.4 bar.
Î Write the new signal pressure range of
1.6 to 2.4 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 over-
sized 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 50 valve with 15 mm rated
travel and 750 cm² actuator with 30 mm rat-
ed travel; 0.2 to 1 bar bench range.
At half the valve travel, the operating range
is between 0.2 and 0.6 bar.
Mounting and start-up
25