Selection of flow meters and control valves
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We have several control valves here with their set points set at 100, yet the amount of material fed in is less than half of the flow meter’s range. When a higher volume of material is needed, a bypass must be used to supply it. At first, we thought that impurities in the pipes were blocking the valve cores; after removing them several times, we found that they were clean inside. We also checked the entire pipeline and found no signs of blockages. Then we concluded that the choice of control valves was not suitable for the flow meter’s range. We don’t have any information available regarding the relationship between the diameter of the control valves and the flow meter. Could someone please explain this to us?
First, it is necessary to check the process-related factors; the pressure may not reach the required level after passing through the control valve due to pressure losses, resulting in the situation where even with the control valve set to 100%, the desired pressure is not achieved. Another possibility is that there is an issue with the selection of the control valve itself.
Even with the control valve fully open, the production requirements cannot be met; either there is a blockage in the piping or the piping design is inadequate – it is too small to meet the production needs.
Check whether the pipeline size is too small, and whether the control valve has experienced excessive diameter reduction
The diameter of the control valves is uniformly set at DN25, while the pipeline diameter has been changed from DN32 to DN25
The flow rate range is 0-1200 L/h, with a diameter of DN15; what size regulator is needed to meet the production requirements?
Find a selection guide for control valves or the operating instructions for them (some of which are not available); these documents specify the maximum flow capacity of the control valves, and that will give you the answer. The control valve is DN15; if the pipeline is also DN15, there will be a problem with the piping.
Check the CV value of the control valve.
The CV value of the control valve is 4.0
The CV value is too low; use the selection software to choose a new one!
The CV value of 4.0 for the DN25 control valve is too low; what is the required flow rate? It should be reselected!