Samson 3222/5757 - Manual (Page 4)

1 Design and principle of
operation
The control valves consist of a single-seated
Type 3222 Globe Valve and either a
Type 5757, Type 5757-7 or Type 5724
Controller with Electric Actuator or a Type
5725 Controller with Electric Actuator with
safety function.
The process medium flows through the globe
valve in the direction indicated by the arrow
on the body. The position of the valve plug
determines the flow rate over the cross-sec-
tional area of flow released between the
plug (3) and valve seat (2). The plug stem
(4) with plug is connected with the stem of
the actuator (10) by a force-locking connec-
tion. The valve is opened by the valve spring
(5) following the retracting movement of the
actuator stem. A special version is required
for water above 150 °C and for steam
(Fig. 1). The plug is moved by a change in
the control signal acting on the actuator.
The electric actuator with safety function
(Type 5725) has a spring mechanism and
an electromagnet that can be connected to a
safety control circuit. When the control cir-
cuit is interrupted or the power supply fails,
the magnet disengages the gear from the
self-locking motor and releases the spring
mechanism. The valve is closed in the event
of a safety situation (fail-safe action
“actuator stem extends”).
The electric actuators contain a digital con-
troller integrated into the actuator. The con-
trolled variable is recorded over the directly
connected Pt 1000 sensor (see Table 2).
The output signal of the digital controller
acts as a three-point stepping signal on the
synchronous motor of the actuator and is
transferred over the connected gear as a
positioning force onto the actuator stem.
The Type 5757, Type 5724 and Type 5725
are particularly suitable for DHW heating in
instantaneous heating systems and for fixed
set point control circuits in mechanical engi-
neering applications.
Type 5757-7 is suitable for heating applica-
tions.
1.1 Versions
PN DN EB 1)
Electric control valve/Controller with electric
actuator
Type 3222/5757 2) 25 15 to 25 5757
Type 3222/5757-7 3) 25 15 to 25 5757-7
Type 3222/5724 2) 25 15 to 50 5724
… with safety function
Type 3222/5725 2) 25 15 to 50 5724
1) Refer to the listed Mounting and Operating
Instructions (EB) for details on the controllers
with electric actuators
2) Controller with electric actuator for domestic
hot water heating in instantaneous heating
systems and for fixed set point control circuits
in mechanical engineering applications
3) Controller with electric actuator for heating
applications
4
EB 5766 EN
Design and principle of operation