8
The potentiometer is fitted with a slipping clutch to permit automatic adjustment along with the output shaft.
The anti-condensation heater 8 (Fig.1, 2) prevents water vapours from condensing under the cover of
the control section. The position-limit switching unit and the position transmitter derive their movements from
the output shaft of the actuator via a driving gear (or in the actuators, Type Nos 52 326 and 52 327, via driving
segment 7, as shown in Fig 1). The torque-limit switching unit is driven by a “floating worm“of the manual
control mechanism where the worm displacement is directly proportional to the torque of the actuator output
shaft. This enables the actuator to be switched off immediately the torque on the output shaft to whichthe
torque-limit switching unit has been adjusted, is reached.
Note: The microswitches used are of a single-chamber type, i.e., they can operate as a one-pole cut-out switch
a contact maker or a change-ower switch, whereas the torque-limit switches can be used as cut-out switches
only (see the respective circuit layout).
ADJUSTMENT OF THE ACTUATOR
Stop screws
Stop screws are used to limit the actuator working travel to 90° in compliance with the CLOSED
and OPEN end positions of the valves having no trip dogs of their own. The screw stops are mounted on the
outside of the actuator along with the external protective terminal. When viewing the stop screws, the right-
hand stop screw is designedfor the CLOSED position, whereas the left-hand stop screw is designed for the
OPEN position under the assumption that, when viewing the local position indicator, the output shaft rotates
clockwise in the CLOSE direction of rotation. For adjustment of the stop screws, loosen the stop screws,
move the actuator with valve into the CLOSED position, and turn the corresponding stop screw till
an increased resistance is felt when the screw runs onto the stop face within the actuator. Secure the stop
screw in position by retightening its lock nut. Then, rotate the output shaft of the actuator through a 90° angle
to bring it into the OPEN position and set the OPEN-position stop screw by the same procedure.
Legend:
1 – Position-limit switching unit
2 – Position transmitter (potentiometr)
3 – Torque-limit switching unit
4 – Terminal board
5 – Electric motor
6 – Internal protective terminal
7 – Drive gear (or segment)
8 – Anti-condensation heater
9 – Starting capacitor
Fig. 1 - Control panel (type no. 52 325)
Fig. 2 - Control panel (type no. 52 326 - 52 329)
Note:
The encircled numbers are identical to the numbers of the cam releasing screws of the position-limit switching unit.
