Must a rotameter be calibrated?
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This post was last edited by lanke*123 on 2019-2-19 at 20:19. Some information I found states that since the rotor is calibrated using water and air, if the medium being measured is not these two, then the readings must be corrected. I think this doesn’t seem quite right. For example, if I am actually measuring oil, and the density of the actual oil is the same as the density I designed, then there’s no need for any corrections, right? I would appreciate your advice as well.
There is no need to make adjustments to the rotor based on the conditions of the medium, unless the rotor was not designed for that medium but rather for water; in such cases, a conversion is necessary.
The calibration medium for rotameters is water or air. The density of the actual medium flowing through is already adjusted by the manufacturer before the flow meter is used, allowing for direct reading
The production of the rotor requires the customer to provide the density, which is then converted into a water flow rate using calculation software for measurement. In other words, this rotor can only be used with media of that specific density.
The principle of a rotameter is that the weight of the rotor is balanced by the buoyancy of the fluid. The magnitude of the buoyant force is related to the area of the annular gap at the position of the float (the dial reading) plus the density of the actual flow. However, calibration is performed using water and air at 20 degrees/C and standard pressure; corrections are required to obtain the operational readings. In older rotors, the scale readings correspond to the values under calibrated conditions; to obtain the actual readings under operating conditions, a density correction value is needed, and only after this adjustment can the true readings be obtained. Some laboratory rotors still work in this way. Now, the manufacturer can make adjustments based on the operating conditions you provide; what is marked on the dial is the operating density, and the readings correspond to those operating conditions. For example, a calculation map for methane at 60 degrees/6 barg/10 M3/H. 1. Under calibration selection, refer to the P/T of air. 2. Select an appropriate flow meter and calibrate its scale according to the operating conditions. The first column shows the readings for methane processing, while the second column shows the readings corresponding to air calibration; the ratio of the two is the \"conversion factor\".
Any situation where there is a significant difference from the medium used for factory calibration requires calibration