Samson 3244 - 3 Design and Principle of Operation; Fail-Safe Positions

14 EB 8026 EN
Design and principle of operation
3 Design and principle of oper-
ation
The Type3244 is a three-way valve which
can be used either as a mixing or diverting
valve. The design of the mixing and divert-
ing valves in sizes DN15 to 25 (NPS½ to
1) is identical. The Type3244 Valve is pref-
erably combined with a SAMSON
Type3271 or Type3277 Pneumatic Actuator
(see Fig.3). It can also be combined with
other actuators.
The two seats (4 and 141) and plug with
plug stem (5) are assembled in the body (1).
The plug stem is connected to the actuator
stem (A7) by the stem connector clamps
(A26/27) and is sealed by a spring-loaded
V-ring packing (15). The springs in the pneu-
matic actuator (A) are located either above
or below the diaphragm depending on the
selected fail-safe action (see section3.1). A
change in the signal pressure acting on the
diaphragm causes the plug to move. The ac-
tuator size is determined by the diaphragm
area.
The medium ows through the valve in the
direction indicated by the arrow. A rise in
signal pressure causes the force acting on
the diaphragm in the actuator to increase.
The springs are compressed. Depending on
the selected direction of action, the actuator
stem retracts or extends. As a result, the plug
position in the seats changes and determines
the ow rate through the valve.
In mixing valves, the process media to be
mixed enter at valve ports A and B. The
combined ow exits the valve at port AB (see
Fig.3).
In diverting valves, the process medium en-
ters at the valve port AB and the partial
ows exit at ports A and B (see Fig.4).
3.1 Fail-safe positions
The fail-safe position depends on the actua-
tor used.
Depending on how the compression springs
are arranged in the pneumatic actuator, the
valve has two different fail-safe positions:
Actuator stem extends (FA)
When the signal pressure is reduced or the
power supply fails, the springs move the ac-
tuator stem downward, closing port B in the
mixing valve or port A in the diverting valve.
Legend for Fig.3 and Fig.4
1 Body
2 Flange
4 Top seat
5 Plug (with plug stem)
8 Threaded bushing
(packing nut)
9 Stem connector nut
10 Lock nut
14 Nuts
15 Packing
17 Body gasket
84 Travel indicator scale
141 Bottom seat
A7 Actuator stem
A8 Ring nut
A26/
27
Stem connector clamps