There are many factors that affect the measurement accuracy of metal rotor flow meters. In addition to the design and structure of the instrument itself, the flow characteristics and working conditions of the fluid can also affect the measurement accuracy of the flow meter. The float flowmeter has a wide range of applications and can measure liquids and gases. For gas media, they are affected by parameters such as density, viscosity, temperature, and pressure, resulting in significant differences in on-site operating conditions. We can only choose to establish flow measurement equipment based on its commonality and universality, and use theoretical research or empirical data to analyze the impact of differences in usage conditions on metal rotor flow meters through face testing and provide corresponding formulas. The reasons that affect the accuracy of a float flowmeter can be roughly summarized as follows.
1. Processing accuracy of cone tube and float
The metal rotor flowmeter is calibrated by measuring the height of the flowmeter float and displaying the scale on the panel through the principle of magnetic coupling. Therefore, the uniformity of the taper of the conical tube affects the accuracy. When the uniformity of the cone tube is poor, increasing the number of actual calibration points can improve accuracy.
2. Flow coefficient
The flow coefficient of metal rotor flowmeter is measured from experiments, so it has inherent experimental errors. The accuracy of the C-Re curve has a significant impact on the accuracy of the float flowmeter. Especially at low Reynolds numbers, or when measuring the transition zone between laminar and turbulent flow, it has a certain impact on accuracy, and in this case, real flow verification is used.
3. Accuracy of the standard instrument
The uncertainty inherent in the measuring standard itself affects the accuracy of the flowmeter scale during measurement calibration.
4. Physical conditions
The measurement of fluid density, viscosity, temperature, and pressure on site will also have an impact on the measurement accuracy of flow meters, especially in gas flow measurement scenarios where the viscosity change of high viscosity liquids due to temperature changes affects the measurement accuracy. Factors such as the center of gravity of the float being too high or eccentric can cause it to sway left and right during operation. The rapid rotation of the float, which is off center, will affect the measurement accuracy (at this time, the flow rate is often too large, that is, the float shaking reduces the flow area).
5. Installation verticality
If the metal rotor flowmeter is not installed correctly, it will introduce errors.
7. Human error
Verified by skilled personnel, errors can be kept to a minimum. For example, when using a soap film tube to calibrate a flow meter, the accuracy of the stopwatch and soap film tube volume have been calibrated, but the judgment ability of personnel will affect the reading of the flow meter.
6. The influence of bubbles and attachments
In areas where bubbles enter, the impact on measurement is significant. In low flow situations, especially when bubbles adhere to the float and cone tube, it affects buoyancy and flow area, and special attention should be paid at this time.