Gas Damping Mechanism - Tecfluid M21 Series 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.
REMARK: For gas applications at a pressure higher than the atmospheric pressure, it is
recommended to use the M21 models without valve and install a separate valve at the outlet
of the flowmeter.
M21-H... models do not allow their own valve to be mounted at the outlet, they are only
available with valve at the inlet.
5.2

Gas damping mechanism

M21 ¼" damping mechanism
BSP connection
NPT connection
10
M21 ½" and ¾" damping mechanism
BSP connection
NPT connection