Metering accuracy of flow meters
Thread Content
Dear teachers, I would like to ask: for vortex flowmeters with the same diameter (DN50) but different measurement ranges, will their accuracy levels vary? For example, within the specified range of the maximum scale, is it more accurate at higher scales and less accurate at lower scales?
Each diameter of vortex flow meter has a specific range of flow velocities; generally, if you provide the normal flow velocity, the manufacturer will use selection software to determine whether it is necessary to reduce the pipe diameter in order to improve measurement accuracy. The measurement accuracy remains the same for flow meters of the same diameter
The measurement accuracy is influenced by many factors, such as the validity of the parameters provided regarding the mesons (maximum pressure, operating pressure, temperature, maximum flow rate, minimum flow rate, typical flow rate, etc.; the manufacturer then designs and manufactures the device based on these parameters), proper installation (which is particularly important), the range of the flow meter (the difference between the upper and lower measurement limits), and the appropriateness of the selected parameters. Generally, it is best for the typical flow rate to be around 70% of the flow meter’s upper limit.
Vortex flow meters have accuracy that is related to the minimum flow velocity. The flow rate corresponding to 20,000 Reynolds numbers is the value that ensures its accuracy (for large diameters of 6 inches or more, it is 40,000 Reynolds numbers); this corresponds to approximately 0.75% for liquids and 1% for gases. The various manufacturers are more or less the same; it’s just a nominal precision, a sample indicator, while there are differences in actual application.
Vortex flowmeters of the same caliber (DN50) but with different measurement ranges have the same accuracy. Since it is within the specified range of the maximum scale, the high-scale version is more accurate than the low-scale version.
There are existing vortex flowmeters A, B, and C, all with a diameter of DN50. Models A and B have an accuracy class of 1.5, while model C has an accuracy class of 1.0. The range of measurement for models A and C is 4–40 M3/H, whereas the range for model B is 10–30 M3/H. When the flow rate of the medium is 20 M3/H, the error for model A is ±0.3 M3/H, the error for model B is also ±0.3 M3/H, and the error for model C is ±0.2 M3/H. So, in theory, measurement accuracy has nothing to do with the range; it depends only on the accuracy class of the flow meter.