Operation; Three-Step Control; Positioner; Manual Mode - Samson 3274 Mounting And Operating Instructions

8 Operation

8.1 Three-step control

The actuator stem of the version with three-
step signal is moved in the corresponding di-
rection by applying a signal to the terminal
eL or aL.
A constant supply voltage must also be ap-
plied to the actuator to allow it to operate
(see the 'Installation' section).

8.2 Positioner

The positioner ensures a predetermined as-
signment of the valve position to the input
signal. The position feedback is provided as
a current signal at terminals 31 and 32 and
as a voltage signal at terminals 32 and 33
(see the 'Installation' section).
Note
The following applies to split-range
operation: to prevent that the valves overlap,
a dead band of e.g. ±0.5 mA must be
added (see the 'Design and principle of
operation' section). In this case, valve 1 must
be adjusted from 11.5 to 4 mA and valve 2
from 12.5 to 20 mA (corresponding values
apply to voltage input signals).
EB 8340 EN

8.3 Manual mode

Electric override
(Types 3274-11 to -14, -22 and -23)
The actuator stem can be retracted or ex-
tended by pressing one of the two pushbut-
tons located on the side housing cover. In
this way, the attached valve can be brought
into the required position.
After releasing the button, the actuator fol-
lows the control signal of the controller
again.
Note
If the priority of the control signal (e.g. upon
start-up of the plant) is to be interrupted and
the control valve is to remain in a certain po-
sition, disconnect the isolating terminal 81
(see Fig. 8-1).
Î To do this, proceed as follows:
1. Switch off the supply voltage.
2. Unscrew the two fastening screws and
remove the side housing cover.
3. Position a screwdriver at the isolating ter-
minal 81 underneath the release button
and lever up the button until it engages
(the red marking pin is hidden).
4. Refasten the side housing cover.
5. Reconnect the supply voltage.
Operation
8-1