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2
Design and principle of
operation
The actuator in the three-point stepping ver-
sion consists of a reversible synchronous
motor and a maintenance-free gear.
The version with digital positioner contains a
stepper motor which can be supplied with
any voltage regardless of the frequency.
Actuator and valve are connected (force-
locking) over a coupling nut (6). An interme-
diate insulating piece can be used for insu-
lated pipelines.
The medium flows through the single-seated
globe valve in the direction indicated by the
arrow. The position of the plug (3) deter-
mines the flow rate across the area released
between plug and valve seat (2).
The linear actuating force is transmitted di-
rectly over the actuator stem (7) to the plug
stem (5). When the actuator stem extends,
the valve plug (3) moves in the closing direc-
tion. The plug stem follows the actuator stem
owing to the force of the valve spring (4) as
the actuator stem retracts, causing the valve
to open.
Design and principle of operation
1
Valve body
1.1 Connection nut with gasket and
welding ends (accessories)
2
Seat
3
Plug
4
Valve spring
5
Plug stem
6
Coupling nut
7
Actuator stem
Fig. 1 · Type 3222 N/5857 Control Valve
Type 5857
Actuator
EB 5867 EN
5
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