SVI-II Instruc Man.book - Fagerberg

Installation and Set Up
Mounting the SVI II AP on Rotary Valves
Figure 7
Model 33 Actuator
Rotary - 90 Degree
For actuators with 60 to 120 degrees rotation, follow the instructions in
“Mounting the SVI II AP on Rotary Valves” on page 10 except mount the
magnet at plus or minus 45 degrees while the actuator de-energized as
shown in Figure 7 on page 13.
Magnet Orientation on Rotary Valve Shafts
The same mounting hardware is used for Models 35, 30 actuators. For each
actuator type the magnetic coupling must be properly oriented to the active
sensing angle of the positioners Hall Effect sensor. The active range of the
Hall-Effect sensor is plus⁄minus 70 degrees from the null magnet axis. If the
total valve travel is less than 60 degrees, allowing a margin for tolerances, the
best accuracy is achieved by mounting the magnet with the axis vertical in the
valve-closed position. Note the location of the magnets in the ring of the
magnet holder. The axis of the magnets is the line through the centers of both
magnets. Mount the magnet holder with the magnet axis vertical on the 35, 30
when the valve is closed. If travel of the valve exceeds 60 degrees, the
magnet must be assembled to the rotary valve shaft so that the magnet axis is
vertical when the valve is at mid-scale.
Dismantling the SVI II AP from Rotary Valves
Before carrying out any work on the device, power off the instrument or make
sure that the device’s location conditions for potentially explosive atmosphere
permit the safe opening of the cover.
To remove the SVI II AP positioner from a rotary valve perform Steps 1 - 8 on
page 7 in reverse.
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