Issues with flowmeter selection?
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The flow rate of the demineralized water in our plant is measured using orifice plate meters, but current operations show that these meters provide inaccurate readings. We plan to upgrade the measurement system and are wondering which type of flow meter would be suitable. Thank you! Note: The pipeline cannot be filled with fluid
Indeed, if the flow tube is not filled to capacity, many flow meters cannot provide accurate measurements; standard throttling devices, vortex flow meters, and electromagnetic flow meters all require a full and stable flow rate in the pipeline. Especially orifice plates, which do not have high precision and have a small range ratio; therefore, they are even less accurate under your current processing conditions. Positive displacement flowmeters can be considered, such as gear flowmeters, Roots flowmeters, or vane flowmeters.
With your process, in theory a mass flow meter can be used, but it requires that the gas-liquid ratio of your fluid not change too much； Otherwise, the measurement will be inaccurate. Moreover, mass flow meters are expensive, and they also cause high pressure losses! ! It seems that other types of flowmeters have not successfully addressed the issue of measuring gas-liquid two-phase flows. You can make some adjustments to the process so that the flow meter is installed in a fully filled pipe.
It is recommended that you consider positive displacement flowmeters such as oval wheel flowmeters or twin rotor flowmeters
Appropriate modifications can be made to the process piping; vortex flow meters or throttling devices can be used on the vertical sections