Samson 3525 Mounting And Operating Instructions - Ation
12
EB 8823 EN
Design and principle of operation
3 Design and principle of oper-
ation
The single-seated Type 3525 Globe Valve is
combined with a SAMSON Type 3571
Pneumatic Actuator (see Fig. 4).
The seat (4) 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) and is sealed
by a spring-loaded V-ring packing (16). The
springs in the pneumatic actuator (A) 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 medium flows through the valve in the
direction indicated by the arrow. The stan-
dard valve body version normally operates
in the flow-to-open direction (FTO). The me-
dium flows across the plug from bottom to
top. The compact valve body versions nor-
mally operate in the flow-to-close direction
(FTC). The medium flows across the plug
from top to bottom.
The valves have a safety bleed to detect
damaged or worn O-rings.
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
and determines the flow rate through the
valve.
There are three versions available:
−
Standard globe valve with flanges (see
Fig. 3) or threaded ends
−
Compact globe valve with threaded ends
−
Compact T-pattern valve with threaded
ends (see Fig. 5)
Standard globe valves >Class 900 with FKM
O-ring are equipped with an additional sup-
port ring (244) which is inserted into the
groove of the bottom O-ring (17).
Compact T-pattern valves are equipped with
a screw plug (112). The screw plug can be
positioned either at the bottom outlet or –
depending on the flow direction – at the side
outlet. It must not be positioned at the inlet.
Actuators
In these instructions, the combination with a
Type 3571 Pneumatic Actuator is described.
The pneumatic actuator for the standard ver-
sion can be replaced by another Type 3571
Pneumatic Actuator in a different size, but
with the same travel.
Î
Observe the maximum permissible actu-
ator force.
If the travel range of the actuator is larger
than the travel range of the valve, the spring
assembly in the actuator must be preloaded
so that the travel ranges match. See associ-
ated actuator documentation.
Note