10
EB 8314 EN
Design and principle of operation
3 Design and principle of oper-
ation
The double-acting Type 3275 Pneumatic
Piston Actuator with 314, 490, and 804 cm²
actuator areas is mainly mounted on PSA
valves (e.g. Type 3241-PSA).
The actuator mainly consists of the base
(A4), cover (A10), and piston (A9). The stem
connector clamps connect the actuator's pis-
ton rod (A1) with the plug stem of the globe
valve.
The signal pressure p
st
creates the force
F = p
st
· 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
3
/
8
or G ½).
The actuators with 314 and 490 cm²
actuator areas are fixed to a yoke, which is
designed to accommodate a pneumatic or
electropneumatic positioner. See Fig. 2.
A1
A2
A7
A8
A9
A3
S
S
A10
A4
A5
A5
A1
Piston rod
A2
Piston rod seal
A3
Plain bearing
A4
Base
A5
O-ring
A7
Piston seal
A8
Piston guide band
A9
Piston
A10
Cover
S
Signal pressure connection
Yoke
Fig. 2:
Type 3275 Actuator (314 and 490 cm²)