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Design and principle of operation
to the actuator is required. Refer to the asso-
ciated 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.
Mounting with crossbeam
A26
A10
A18
•
A14
A13
A3
•
A30
A11
A1
Vent plug
A2
Bottom diaphragm case
A3
Actuator stem
A10 Spring
A11 Rod
A12 Bushing
A13 Diaphragm plate
A14 Diaphragm plate
Fig. 3-1: Functional diagram of Type 3371 Actuator with 120 cm² actuator area
3-2
•
•
•
•
3.3 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.
Mounting without crossbeam
A16
A2
•
•
A1
•
•
A35
A17
A16 Top diaphragm case
A17 Bracket
A18 Diaphragm
A26 Collar nut
A30/
Stem connector clamps
A31
A35 Pneumatic connection
A72 Rod nut
•
•
•
EB 8317 EN
A31
A12
A72
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