Samson 4785, Mounting And Operating Instructions

Page: 14 / 78

symbol on the block. This means, the
adjusted symbol for "Actuator stem ex-
tends" or "Actuator stem retracts" must
match the actuator version used.
If necessary, remove the two fastening
screws and switch plate, turn the plate
by 180° and remount it.
7. Place the connection block with its seal-
ing rings against the positioner and ac-
tuator yoke, and screw it tight using the
fasting screw.
For actuators with fail-safe action "Actu-
ator stem retracts" additionally install
the prefabricated signal pressure tube
between connection block and actuator.
120 cm
2
Actuator
For Type 3277-5 Actuators with 120 cm 2 ,
the signal pressure is transmitted to the dia-
phragm chamber via the switchover plate
(Fig. 3, bottom).
Note!
For a rated travel of 7.5 mm, a brass
throttle (see table Accessories on page 15)
must be pressed into the seal located in the
signal pressure input on the actuator yoke.
With 15 mm rated travel, this is only re-
quired if the supply pressure exceeds 4 bar.
6. Remove the screw at the back of the po-
sitioner and close the signal pressure
output (output 38) at the side with the
associated plug included in the acces-
sory kit.
7. Mount the positioner so that the bore in
the distance plate (15) is aligned with
the seal located in the bore of the actua-
tor yoke.
8. Align the switchover plate with the
corresponding symbol for attachment
on the left side, and screw the plate to
the actuator yoke.
Note!
If, in addition to the positioner, a solenoid
valve or a similar device is attached to the
120 cm 2 actuator, the rear M3 screw must
not be removed. In this case, the signal pres-
sure has to be fed from the signal pressure
output to the actuator via the required con-
necting plate (see Table 2). The switchover
plate is no longer required.
Note!
(for all actuators)
For faster control valves with a transit time
< 0.6 sec., replace the filter in the signal
pressure output (output 38) with a screw-in
throttle (see table Accessories), if necessary,
to improve the control properties.
Filling the spring chamber with air
If the spring chamber of the Type 3277 Ac-
tuator must be filled with the air exhausted
from the positioner, the spring chamber (ver-
sion "Actuator stem extends") can be con-
nected to the connection block by means of
a tube (Table 3). To do so, remove the vent
plug on the connecting block.
With Type 3277-5, version "Actuator stem
retracts", the air exhausted from the posi-
tioner is constantly applied to the spring
chamber via an internal bore.
14
EB 8382-2 EN
Attaching the positioner