Samson 3277 - Markings on the Device

EB 8310-6 EN 3-3
Design and principle of operation
signal pressure connection on the top dia-
phragm case.
The direction of action can be reversed (see
the 'Service and conversion work' section).
3.4 Signal pressure routing
3.4.1 Type3271
In the "actuator stem extends" version, the
signal pressure is routed through the bottom
signal pressure connection (S) to the bottom
diaphragm chamber and moves the actuator
stem (A7) upward opposing the spring force
(see Fig.3-1, right).
In the "actuator stem retracts" version, the
signal pressure is routed through the top sig-
nal pressure connection (S) to the top dia-
phragm chamber and moves the actuator
stem (A7) downward opposing the spring
force (see Fig.3-1, left).
3.4.2 Type3277
In the "actuator stem extends" version (see
Fig.3-2, right), a signal pressure connection
(S) is located on the side of the yoke which is
connected to the bottom diaphragm cham-
ber over an internal hole. The signal pres-
sure moves the actuator stem upward oppos-
ing the spring force. A positioner can be
connected using a connection block at this
point. No additional piping to the actuator is
required. Refer to the associated positioner
documentation for more details.
In the "actuator stem retracts" version, simi-
lar to Type3271, the signal pressure is rout-
ed through the top signal pressure connec-
tion (S) to the top diaphragm chamber and
moves the actuator stem (A7) downward op-
posing the spring force (see Fig.3-2, left).
3.5 Fail-safe action
The listed fail-safe actions apply to SAM-
SON Series240, 250, 280 and 290 Valves
(globe valves).
When the signal pressure is reduced or the
control signal fails, the fail-safe position of
the control valve in throttling or on/off ser-
vice depends on whether the springs are in-
stalled in the top or bottom diaphragm
chamber.
Version with handwheel: in the active man-
ual mode (the handwheel is not in the neu-
tral position), the valve is not moved to the
fail-safe position even upon failure of the
supply air.
3.5.1 Version with direction of
action "actuator stem
extends"
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.
Note