I have questions regarding level control.

It can only be said that we can roughly estimate its traffic volume? 1. First, you need to know the flow characteristics of your control valve. 2. Determine the percentage flow rate at the corresponding opening degree using the flow characteristic curve. 3. Calculate the flow value by designing the percentage corresponding to full scale*.

The actual flow rate is related to both the valve opening degree OP value and the flow characteristic/distribution pressure drop. If the actual distribution pressure drop is similar to the design value, then the opening degree ------- Cv value ------- flow rate. However, the actual operating pressure drop is very likely to differ significantly from the design value, especially in liquid-phase systems; it is best to determine the actual pressure drop of the valve in order to calculate the flow rate more accurately. The opening degree does not fully represent the flow rate; for example, if I deliberately reduce the size of the manual valve downstream of the control valve, this will cause the control valve to open wider, but in reality the flow rate in the pipeline will definitely decrease.

Excuse me, is the formula for the opening degree op value = flow rate/CV value correct?

Hello, may I ask what is a suitable value for the full-scale flow rate of a control valve?

Look at the definition of this CV value: when the pressure before and after the valve is constant, say 100 kPa, it represents the water flow rate when the valve is fully open, for example, 50. Then your formula holds, provided that you explain it under specific conditions.

It is possible to conduct a theoretical calculation, though the results are not very accurate; it is also necessary to know the flow rate when the valve is fully open under operating conditions, as well as whether the valve behaves linearly

The common relationships between the signal value on the control valve (OP: 4~20mA) and the valve opening degree (0~100%) are linear and proportional to 100%. The flow rate corresponding to the maximum valve opening is the maximum flow rate. The maximum flow rate passing through the valve is related to both the valve opening and the pipe resistance (depending on the pressure drop distribution coefficient s; when s=1, the valve exhibits theoretical behavior, and it is generally considered that the flow rate becomes uncontrollable when s≤0.3). The actual characteristics of the valve are related to the pressure difference distribution coefficient s; the smaller s is, the more severe the distortion of the flow characteristics becomes, and the lower the maximum flow rate through the valve. In summary, it is difficult to accurately calculate the actual flow rate using OP.

The full-scale value is generally determined by various factors such as valve characteristics and process requirements!

If it can be calculated, then there’s no need for a flow meter. Additionally, two pressure transmitters can be installed for import and export, and the value is calculated based on the differential pressure; the control valve itself functions as a throttling device.