Design And Principle Of Operation; Direction Of Action And Fail Position - Samson SS AT054U Mounting And Operating Instructions

3 Design and principle of operation

The SAMSON SAMSON ROTACTOR RP 3171 ("S" Series)
actuators are devices for remote operation (on/off or modula-
ting duties) of different industrial valves such as ball valves,
butterfly valves and plug valves.
The actuators are available in two configurations: double ac-
ting and single acting.
1. DOUBLE ACTING
Refer to Fig. 3-2.
In case of the double acting configuration air pressure will be
necessary for both strokes (A and B).
A
"2"
B
"2"
Fig. 3-1
2. SINGLE ACTING
Refer to Fig. 3-1.
When air pressure is supplied through port "2" (A') into the
actuator body, the linear force applied on the piston surface
generates the pinion rotation, driving the valve to a defined
position. At the same time the actuator springs are compres-
sed.
When air pressure is discharged (B'), the springs are auto-
matically released, driving the rack and pistons back to the
original position and thus the valve to the fail-safe position.
A'
"2"
B'
"2"
Fig. 3-2
EB 8326 EN
"4"
"4"
"4"
"4"
The actuators can be controlled by different options:
− for SS AT054U → SS AT404 direct mounting of control
devices (for example a solenoid valve or a manifold) with
NAMUR interface.
− for SS AT454 → SS AT654 threaded connections (to pres-
surize port "2" and "4") with air lines from separate elec-
tro-pneumatic control system.
3.1 Direction of action and fail positions
The standard rotating direction for the "S" Series actuators is
clockwise to close.
Standard "S" Series actuators are designed for 90° rotating
angle, with travel stop allowing adjustment (Fig. 3-3) for ±5°
on both closed and open positions.
90°
95° 85°
Fig. 3-3
For single acting actuators in case of pressure, power or
signal failure the springs drive the actuator in the fail position
that can be FAIL OPEN or FAIL CLOSE.
Note
If the actuator is controlled by a control system the FAIL positi-
on may be different from FAIL OPEN or FAIL CLOSE.
Î Refer to the actuator model technical data for the FAIL po-
sition.
Î Refer to section 2.1 'Actuator nameplate sample' (Table
2-1, position 11) for the fail action and direction of rotati-
on available options.
Design and principle of operation
Available stroke
adjustment
5°
0°
-5°
3-1