Fail-Safe Action; Version With Direction Of Action "Actuator Stem Extends" (Fa); Version With Direction Of Action "Actuator Stem Retracts" (Fe); Versions - Samson 3277 Mounting And Operating Instructions

Design and principle of operation

3.5 Fail-safe action

When the signal pressure is reduced or the
control signal fails, the fail-safe position of
the control valve depends on whether the
springs are installed in the top or bottom di-
aphragm chamber.
Note
The listed fail-safe actions apply to
SAMSON Series 240, 250, 280 and 290
Valves (globe valves).
3.5.1 Version with direction of
action "actuator stem
extends" (FA)
When the signal pressure is reduced or the
control signal fails, the springs move the ac-
tuator stem downward and close the globe
valve. The valve opens when the signal pres-
sure is increased enough to overcome the
spring force.
3.5.2 Version with direction of
action "actuator stem
retracts" (FE)
When the signal pressure is reduced or the
control signal fails, the springs move the ac-
tuator stem upward and open a mounted
globe valve. The valve closes when the signal
pressure is increased enough to overcome
the spring force.
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3.6 Versions

Type 3271 and Type 3277 Pneumatic Actua-
tor (175 and 750 cm²):
− Standard version
The top and bottom diaphragm cases are
made of plastic-coated sheet steel.
− Corrosion-resistant version
The top and bottom diaphragm cases are
optionally available made of stainless
steel 1.4301.
− Version with handwheel
The Type 3271 and Type 3277 Actuators
can be fitted with an additional hand-
wheel to manually adjusted the actuator
stem position.
− Version with side-mounted handwheel
The Type 3271 and Type 3277 Actuators
can be combined with a Type 3273
Side-mounted Handwheel with max.
30 mm travel (u T 8312).
− Travel stop
The Type 3271 and Type 3277 Actuators
can be fitted with a mechanically adjust-
able travel stop in a special version. The
travel is reduced by up to 50 % in both
directions of action (stem extends or re-
tracts).

3.7 Technical data

The nameplate provides information on the
actuator version (see section 2.1).
EB 8310-5 EN