Is there no flow issue after the control valve?

Hehe, the control valve on your pipeline itself is used to regulate the flow rate. Moreover, the internal components of such control valves create resistance and cause a reduction in the pipe diameter; as a result, the flow rate decreases when the valve is fully open. If there is no flow rate even when the valve is fully open, then you need to specify the type of flow meter and its installation method

First, it is possible to check whether the calculation sheet for the control valve is satisfactory； Next, check whether it is a problem with the flow meter.

After passing through the control valve, the flow rate decreases. First, it is necessary to determine the opening degree of the control valve; the flow rate at that opening degree can be estimated and compared with the value shown by the flow meter. If the pressure difference is high, the valve should be checked first; once the valve is ruled out as the cause, the flow meter should be inspected. First, check whether the flow meter is installed as required, whether its design is reasonable, and whether there are any leaks. Also, consider the actual usage conditions – it’s possible that the volume of flow itself is not high.

As long as the valve operates properly, there is a problem with the connection between the valve core and the valve stem; additionally, it’s possible that the medium inside the pipeline has crystallized or solidified at the valve’s outlet. Remove the valve to check this.

There might be a calculation issue; with valves that have a linear flow characteristic, the flow rate changes significantly at low opening degrees.

1. It may be caused by squaring both the transmitter and the DCS. 2. It is caused by the reverse connection of the positive and negative pressure chambers of the transmitter and an incorrect installation direction of the throttling device. 3. It is caused by the flow meter having wires connected in reverse. 4. The air supply pressure to the control valve is insufficient, there are foreign objects stuck in it, or the wires of the control valve are connected incorrectly.

If all the control valves have been checked and it is confirmed that they are fine, then check the flow meter. Check what type of flow meter you have, and see whether the calculation documents match the process conditions as well as to determine if there is multiphase flow. If it is a orifice plate, then focus on checking whether the orifice plate is installed in the wrong direction, and whether duplicate square-root calculations have been performed (check both the transmitter and the configuration).

What type of flow meter is it? Vortex flow meter or orifice plate? Does the flow meter not give accurate readings when a bypass line is used?

The function of a control valve is to regulate flow; it’s normal for the flow rate to be lower. I’m not sure exactly what you mean – it would be helpful to have some data so that I can assist you in analyzing the situation. For example, if you require a flow rate of 50, but only 10 can be achieved, or perhaps the valve isn’t fully open enough to meet your flow requirements I suggest checking from the following aspects: 1. Examine problems with the control valve itself, such as whether the valve core has fallen off This results in the valve stem moving normally while the valve core remains stationary; therefore, it cannot be detected through visual inspection or other feedback mechanisms ； Also, when the actuator moves, does the valve stem move as well? Check the connection between the valve stem and the actuator; if it comes loose, the actuator will operate while the valve stem remains stationary ； There is also the selection of the valve body – what kind of valve? Single-seat globe valve? Can the motor torque of the actuator counteract the unbalanced force? Wait, many factors need to be taken into consideration. 2. Issues with the flow meter: whether it is functioning properly, and whether there are any blockages or leaks in the positive pressure chamber, etc ； Also, what kind of flow meter or throttling element is being used? Could it be installed backwards? Since your control valves are installed in the wrong direction, could it be that the construction team got the flow direction wrong? If the flow meter is installed in reverse, the reading will be lower. If there are no issues with flow measurement, then thirdly, the process team should calculate what the flow rate would be at full speed under normal pressure conditions, assuming that there are no throttling elements in the pipeline; this will help determine whether the pipeline is too narrow Fourth, some valves in front of the pipeline are not open; can a pressure gauge be installed elsewhere to measure the pressure there?