Basic knowledge

Customer issues

Scene 1

      The customer's gas source pressure is relatively low. After connecting the YIDU flow controller and a throttling element at the outlet to the atmosphere, it was found that the flow could not be controlled to the set value.

Scenario 2

The customer suspects that there is a problem with the flow meter as one of the gas paths cannot achieve the original gas output after adding it.

Root cause

Question 1: Why can't the flow controller control the flow well?

Question 2: Why can't the original gas output be achieved by adding a flow meter to the gas pipeline?

Answer: The flow meter and flow controller did not obtain sufficient differential pressure.

        
Problem analysis

Flow is generated by the flow of gas, and gas always flows from high pressure to low pressure. There is a differential pressure between the "high pressure" and "low pressure" areas here. Without this differential pressure, the so-called "high pressure" and "low pressure" areas would have the same pressure, and gas would not flow. This seemingly simple principle is the key to understanding the working principles of flow meters and flow controllers.

 Whether it is a flowmeter or a flow controller, the inlet pressure must be higher than the outlet pressure during normal operation, otherwise the gas will not flow. The differential pressure between the inlet and outlet ends is the differential pressure required for the operation of the flowmeter and flow controller. For the flowmeter, this differential pressure is the pressuer drop generated during its operation, and for the flow controller, it is the required working differential pressure. Gas flows through flow meters or flow controllers, and after rectification, sensor detection, nozzle control, and other processes, the pressure will continuously decay due to collision with the wall. This is a common characteristic of all types of flow meters and flow controllers, and there is no flow meter or flow controller without pressuer drop.

Selection Recommendations

If the pressure state in the user's usage scenario is indeed critical and they hope that the flowmeter and flow controller can work even under very small differential pressures, they can choose flowmeters and flow controllers with low pressuer drop or extremely low pressuer drop.