Samson Type 3766, Mounting And Operating Instructions

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3 Connections
3.1 Pneumatic connections
The air connections are either 1/4 NPT or
G 1/4 tapped holes. The customary screw
joints for metal and copper tubes or plastic
hoses can be used.
Important!
Make sure that the supply air is dehumidi-
fied and free of oil and dust. Observe the
maintenance instructions for upstream press-
ure reducing stations.
Thoroughly purge all air tubes and hoses
before connecting them.
When attaching the Type 3277 Actuator di-
rectly, the signal pressure connection is
fixed. When using NAMUR attachment, the
signal pressure line is connected to either
the upper or lower diaphragm chamber of
the actuator depending on the actuator’s
fail-safe action, i.e. “Actuator stem retracts”
or ”Actuator stem extends”.
Exhaust air
Positioners with model index 3766-x...x. 03
and higher are equipped with a hinged
cover without a vent connection. The re-
quired exhaust air connection for these
models are now included in the mounting
accessories.
For direct positioner attachment, the vent
plug is located on the plastic cover of the ac-
tuator; for NAMUR attachment, it is located
on the adapter housing; and for attachment
to rotary actuators the vent plug can be
found on the intermediate piece or the re-
versing amplifier.
Important!
When using older models with indices up to
3767-x...x. 02 , mounting parts will have to
be replaced as well.
3.1.1 Pressure gauge
To monitor the positioner, we recommend to
install pressure gauges for the supply air
and the signal pressure.
The required parts are listed as accessories
in Tables 4, 5 or 7.
3.1.2 Supply pressure
The required supply pressure depends on
the bench range and the direction of action
(fail-safe action) of the actuator.
The bench range is indicated on the name-
plate as either spring range or signal press-
ure range, depending on the actuator ver-
sion used. The fail-safe action is indicated
by either FA (stem extends) or FE (stem re-
tracts), or by a corresponding symbol.
Actuator stem extends (FA):
fail-safe position "valve CLOSED"
(for globe and angle valves)
Required supply pressure =
upper bench range valve + 0.2 bar,
at least 1.4 bar
28
EB 8355-1 EN
Pneumatic connections