Design And Principle Of Operation; Fail-Safe Positions - Samson 3259 Translation Of Original Instructions

Design and principle of operation

3 Design and principle of oper-
ation
The Type 3259 High-pressure Angle Valve is
preferably combined with a SAMSON
Type 3271 or Type 3277 Pneumatic Actuator
(see Fig. 3). It can also be combined with
other actuators.
The seat (4) and plug with plug stem (5) are
installed 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 double PTFE
packing (15). Alternatively, an adjustable
high-temperature packing can be used. The
springs in the pneumatic actuator are locat-
ed either above or below the diaphragm de-
pending 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 actuator size is determined by the
diaphragm area.
The medium flows 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
1 Body
2 Intermediate piece
4 Seat
5 Plug
7 Guide bushing
8 Threaded bushing
(packing nut)
10 Lock nut
14
stem retracts or extends. As a result, the plug
position in the seat changes and determines
the flow rate through the valve.

3.1 Fail-safe positions

The fail-safe position depends on the mount-
ed actuator. Depending on how the com-
pression springs are arranged in the pneu-
matic actuator, the valve has two different
fail-safe positions:
Actuator stem extends (FA)
When the signal pressure is reduced or the
air supply fails, the springs move the actua-
tor stem downward and close the valve. The
valve opens when the signal pressure is in-
creased enough to overcome the force exert-
ed by the springs.
Actuator stem retracts (FE)
When the signal pressure is reduced or the
air supply fails, the springs move the actua-
tor stem upwards and open the valve. The
valve closes when the signal pressure is in-
creased enough to overcome the force exert-
ed by the springs.
14 Body nut
15 Packing
17 Body gasket (lens ring
gasket)
56 Threaded flange
57 Threaded flange
60 Yoke assembly
92 Castellated nut
111 Threaded flange
A4 Diaphragm
A7 Actuator stem
A8 Ring nut
A10 Spring
A26/27 Stem connector clamp
S Signal pressure
connection
EB 8059 EN