Gas Damping Mechanism - Techfluid SC250H Instruction Manual

If the regulation is done using the shut off valve, in open circuits or at low gas flow in the
meter, the gas will expand which will sharply diminish its density, providing very serious
reading errors.
If the flow is regulated by the shut off valve, the float usually experiences an oscillating
movement which produces a shut off action until sufficient pressure is gained to overcome its
weight. The sudden fall of pressure, when the gas escapes, will make it fall. This cycle is
repeated generating an oscillating measurement (resonance).
In applications where the gas outlet is at atmospheric pressure, install the regulating valve
upstream of the flowmeter if the flowmeter was calibrated at atmospheric pressure. The shut
off valve is then installed downstream of the flowmeter and it should be fully open.
The valve opening procedure should be as following:
- With the regulating valve closed, fully open the shut off valve.
- Gradually open the regulating valve until the desired flow rate.
And for closing:
- Close the regulating valve gradually until zero flow rate.
- Fully close the shut off valve to isolate the flowmeter.
Operating in a different way may involve water hammers that can damage the meter reading
or generate instabilities.
5.2

Gas damping mechanism

1. Upper float stop
2. Float
3. Piston
4. Piston locking circlip
5. Guide cylinder
6. Circlips for locking upper float stop & guide cylinder
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