Samson Series 420 Manual - 7 Connections
26
EB 7500 EN
Connections
7 Connections
7.1 Pneumatic connections
The pneumatic connections are designed as
a bore with
1
/
8
NPT thread. Customary fit-
tings for tubing or plastic hoses can be used.
Make sure the supply air is dry as well as
free of oil and dust.
Read the maintenance instructions for up-
stream pressure reducing stations.
Blow through all air pipes and hoses thor-
oughly before connecting them.
The threaded holes on the connecting plate
(depending on the type and circuit version)
which are not used must be sealed with stop-
pers with
1
/
8
NPT thread.
The port labeling is as follows:
S Switching pressure (0/1.4 bar)
Sealed in Type 3422 Manual Control
Station, open in Type 3427 Pneumatic
Manual Control Unit when used with
controller for control room or field instal-
lation (except with P and V controller
module)
Output in Type 3427, input in
Types 3423 and 3425.
On switching the manual control station to
manual, a switching pressure of 1.4 bar is
applied to the start-up relay to bypass the Tn
and Tv restrictors.
yA Automatic output pressure (0.2 to
1 bar)
Sealed in Type 3422, open for separate
instrumentation with Type 3427 Pneu-
matic Manual Control Unit
Output in Types 3423 and 3425, input
in Type 3427.
w Reference variable (0.2 to 1 bar)
Sealed in Type 3422, open in
Type 3427.
Output in Type 3427, input in
Types 3423 and 3425.
Z Supply air
Supply air 1.4 ±0.1 bar.
R Feedback(input 0.2 to 1 bar)
Sealed in Type 3422 in delivered state
(R and y are internally connected on the
connecting plate).
If R and y ports are to be connected exter-
nally (Fig. 16, top), unfasten the connecting
plate and move the O-ring to the feedback
port (y and R are then separated from one
another). Remove the stopper at the R port
and replace it with a screw fitting.
w
ext
Externalreferencevariable
(input 0.2 to 1 bar)
To feed forward the reference variable
externally when selector switch is set to
w
ext
.
x Controlledvariable(input 0.2 to 1 bar)
Input signal, output signal from transmit-
ter
NOTICE
!