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3.2 Adjusting actuators with open fail-safe action "Air to close"
Zero (starting point)
1) Use an ammeter to adjust the input signal to 20 mA.
2) Remove the cover plate and turn the zero adjuster (4, fig.4) until the plug stem
just begins to leave its rest position.
3) Increase the input signal and slowly reduce it again to 20 mA. Check if the plug
stem begins to move at 20 mA.
4) Correct any deviations via the zero adjuster (4, fig.4).
Turning counterclockwise causes the valve to leave its rest position with delay,
whereas turning clockwise causes the valve to leave earlier.
Upper range value
5) Having completed adjustment of the starting point, use the ammeter to adjust
the input signal to 4 mA.
When reaching the upper range value of 4 mA, the plug stem must have passed
through its entire rated travel range of 100 %.
6) Adjust the potentiometer for span (1, fig.4) until the upper range value is correct.
Turning clockwise increases the travel, and turning counterclockwise reduces the
travel.
7) When the correction procedure is finished, increase the input signal again.
First check the starting point (20 mA), afterwards the upper range value (4 mA).
8) Put the cover plate back over the zero adjuster.
9) Plug the jumper on the pins to activate the tight-closing function.
