3 Connections
3.1 Pneumatic connections
The pneumatic connections are designed as
tapped holes with ¼ NPT or G ¼ thread.
The conventional male connections for metal
and copper pipes (or plastic hoses) can be
used.
NOTICE
The supply air must be dry and free of any
oil and dust.
Always observe the maintenance instructions
applicable to the connected pressure reduc-
ing stations. Blow out air lines thoroughly
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
or higher are equipped with a hinged cover
without a vent connection. The required ex
-
haust 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.
Note: When using older models with index
3766-x...x. 02 or lower, 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 is determined
by the bench range and the operating direc-
tion (fail-safe action) of the actuator.
The bench range is written on the nameplate
as spring range or signal pressure range
depending on the type of actuator. FA (actu-
ator stem extends) or FE (actuator stem re
-
tracts) or a symbol indicates the operating
direction.
Actuator stem extends (FA):
Fail-safe position "Valve CLOSED"
(for globe and angle valves)
Required supply pressure =
Upper bench range value + 0.2 bar,
minimum 1.4 bar.
28 EB 8355-1 EN
Connections
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