Versions; Additional Fittings - Samson 3281 Mounting And Operating Instructions

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.
Tip
The actuator's direction of action can be re-
versed, if required. Refer to the mounting
and operating instructions of the pneumatic
actuator:
u EB 8310-X for Type 3271 and Type 3277

3.2 Versions

Insulating section
The modular design allows an insulating sec-
tion to be fitted to the standard valve version.
Installed valves may have a bellows seal fit-
ted on them.
Actuators
In these instructions, the preferable combina-
tion with a SAMSON Type 3271 or
Type 3277 Pneumatic Actuator is described.
The pneumatic actuator (with or without
handwheel) can be replaced by another
pneumatic actuator in a different size, but
with the same travel.
Î Observe the maximum permissible actu-
ator force.
EB 8251 EN
Design and principle of operation
Note
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.
The basic pneumatic actuator can be re-
placed by a pneumatic actuator with addi-
tional handwheel or by an electric actuator
(see Information Sheet u T 8300).
3.3 Additional fittings
Steam trap
Automatic steam traps must be installed at
the lowest point in the upstream and down-
stream lines to ensure proper functioning of
the plant.
Check valve
We recommend installing check valves be-
tween the steam conditioning valve and the
cooling water valve to protect the condensate
system.
Strainers
We recommend installing a SAMSON
strainer upstream of the valve body and in
the inlet pipe for the water supply. It prevents
solid particles in the process medium from
damaging the valve.
Bypass and shut-off valves
We recommend installing a shut-off valve
both upstream of the strainer and down-
stream of the valve and installing a bypass
line. The bypass ensures that the plant does
3-3