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3 Design and principle of oper-
ation
The double-acting Type 3275A Pneumatic
Piston Actuator with 314, 380, 490 and
804 cm² actuator areas is mainly mounted
on PSA valves (e.g. Type 3241-PSA).
The actuator mainly consists of the cover (4),
base (10) and piston (9). The stem connector
clamps connect the actuator's piston stem (7)
with the plug stem of the globe valve.
6
9
44
7
Fig. 3-1: Type 3275A Actuator (314, 380 and 490 cm²)
EB 8314-1 EN
Design and principle of operation
The signal pressure pst creates the force
F = pst · A at the piston surface A, which is
opposed by the corresponding counter-
pressure. The piston is pressurized with the
supply air over the two connections (S; G
or G ½).
The actuators with 314, 380 and 490 cm²
actuator areas are fixed to a yoke, which is
designed to accommodate a pneumatic or
electropneumatic positioner. See Fig. 3-1.
4 Cover
6 Cylinder barrel
7 Piston stem
9 Piston
10 Base
11 Linkage
44 Yoke
10
11
4
3
/
8
3-1
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