Samson 3291, Translation Of Original Instructions

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EB 8072 EN 3-1
Design and principle of operation
3 Design and principle of oper-
ation
The Type 3291 Globe Valve with clamped
seat is preferably combined with a
SAMSON Type 3271 or Type 3277 Pneu-
matic Actuator. It can also be combined with
other actuators.
The seat (4), plug with plug stem (5) and
seat retainer (124) are installed in the body
(1). The seat is inserted into the seat bridge.
The seat and seat retainer are clamped into
place by tightening the body nuts (14). In
versions with flow divider, it takes over the
function as a seat retainer, i.e. the seat (4) is
clamped in place by the flow divider (62).
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 or an adjustable high-tem-
perature packing.
The springs in the pneumatic actuator are lo
-
cated 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 actuator size is deter-
mined by the diaphragm area.
The process medium flows through the valve
in the direction indicated by the arrow on
the body in the flow-to-open (FTO) direction.
A rise in signal pressure causes the force act-
ing on the diaphragm in the actuator to in -
crease. The springs are compressed. De -
pending on the selected direction of action,
the actuator stem retracts or extends. As a
result, the plug position in the seat changes,
which together with the seat retainer's con
-
tour, determines the released cross-section
and the flow rate as well.
We recommend the use of positioners with
integrated diagnostic firmware (see sec-
tion 3.4) for valves used for on/off service.
The partial stroke test included in this soft-
ware helps prevent a shut-off valve normally
in its end position from seizing up or getting
jammed.
Tip
Legend for Fig. 3-1
1 Body
2 Bonnet
4 Seat
5 Plug (with plug stem)
8
Threaded bushing
(packing nut)
10 Lock nut
14
Body nut
15 Packing
17 Body gasket
60
Yoke assembly
92 Castellated nut
124 Seat retainer
125 Spacer ring
126 Seat retainer gasket
127 Seat bridge gasket
A4 Diaphragm
A7 Actuator stem
A8
Ring nut
A10 Spring
A26/
27
Stem connector clamps
S Signal pressure
connection