The fluctuation of the compressed air flow meter is very large
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The thermal mass flow meter we used before was very stable, with readings around 80 cubic feet per second; however, its repair cost was high when it broke down. When we switched to a rotameter, the readings fluctuated greatly, ranging from 0 to the full scale of 300, even though the actual flow rate should have been 80. Is this normal? The gases we use are mainly for valves such as on/off valves and control valves; there aren’t many of them
First, setting aside the issue of precision between the two, the straight section ahead of you is quite short; not to mention vibrations and such at the moment
The straight pipe section should be fine; even if it doesn’t reach 10D, it’s still 8D!
1. Judging from the photos, it has a DN50 diameter; it seems that the straight pipe section is less than 8D or 10D, right? 2. The calibration pressure for the flow meter is 7 bar at room temperature; are the gas pressures in the pipeline subject to large fluctuations? If the fluctuations are large and the conditions deviate from the calibrated pressure and temperature, then the values will definitely be inaccurate. A mass flow meter is ideal; it isn’t affected by pressure or temperature, so it’s definitely accurate.
Top 10 and bottom 5; ideally, the top end should be between 30-50
1. The installation of this metal rotor flowmeter is problem-free, and the straight pipe sections before and after it basically meet the requirements； 2. When measuring gases, metal rotor flowmeters perform compensation and conversion to Nm3/h based on fixed pressure and temperature; this meter performs the compensation and conversion at 0.7 MPaG and 20 degrees Celsius. Obviously, if the range of pressure changes is large, manual conversion is required. Therefore, metal rotameters are not suitable for measuring gases with large pressure variations. On the other hand, thermal mass flow meters are not affected by pressure fluctuations within a certain pressure range. 3. By looking at the photos on site, it can be seen that compressed air enters directly from the tank; if the pressure fluctuates frequently, this can lead to large fluctuations in the pointer reading and inaccurate flow indication. It is recommended to install a pressure regulator at the tank outlet to maintain the pressure at 0.7 MPaG.
The thermal mass meter that was used before. With very small fluctuations
That tank is a compressed air filter; the gas enters from below the flow meter. I would like to ask whether a vortex flow meter is suitable for this application?
Using a metal rotameter to measure gases is suitable when the pressure is stable； It’s not suitable when the pressure is unstable. I guess this metal rotameter doesn’t have a gas damper to smooth out pressure fluctuations.
Even if there are large fluctuations in the thermal type, it cannot reflect them