User Manual - P series
15
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4.2. Procedure A2: Diaphragm-actuated differential instrument
For reasons related to production and metrology, low- and medium-pressure differential instruments are adjusted
relative to each other, with the LP chamber vented to atmosphere.
The procedure is identical to the procedure described in the previous point (A.1. Single instrument).
The HP chamber is connected to the pressure bench, and the LP remains at atmospheric pressure.
4.3. Procedure A3: Bellows-actuated differential instrument
Example: Lower threshold set to 1 bar falling with 10 bar static pressure.
4.3.1. Setting the lower threshold
1. Go up to the desired static pressure in both chambers (10 bar), and stabilise.
2. Isolate both chambers.
3. Create a pressure differential in favour of the HP chamber equal to the desired threshold value “1 bar“
(HP=10 bar, LP=9 bar).
4. Using set point adjustment screw VG, relax range spring RG until the exact point when switch(es) C is/are
triggered on the way up.
5. Retighten and stop at the exact point where switch(es) C is/are interlocked on the way down.
4.3.2. Checking/Adjusting the set points
6. Repeat operations 1 to 3, and then slowly pressurise and depressurise the HP chamber to measure the
changeover value of the switch(es) on the way down.
7. Fine-tune the setting using adjustment screw VG (Lower and Upper threshold control).
8. Disconnect the instrument from the bench.
9. Apply a seal to adjustment screw VG using a Georgin seal kit (torque: 1.7 N∙m ±10%).
10. Close the cover and tighten the two captive screws (torque: 1.2 N∙m).
