Before and after the control valve and the measurement point
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Why is the flow control valve for the purge hydrogen in the UOP reforming unit located after the flow meter, and why is the pressure control valve for the lift gas also located after the pressure gauge?
Your question seems to have been asked without understanding the process, so it’s too limited. It is recommended to understand the principles of the entire process; then this will not be a problem. There’s no need to rush this. It would be good to send over a schematic as well, to facilitate discussion.
Typically, control valves are placed behind the flow meter. As for the pressure control part at the back, it needs to be explained clearly with the previous diagram.
Control valves can easily cause disturbances to the measurement parameters at the front!
In conventional flow control, the flow meter is placed ahead, with the control valve coming after it; this is the case for controlling the flow at the outlet of pumps and machinery as well as the flow of products that are sent out； But the purge hydrogen flow control valve for the UOP reforming is indeed located in front of the flow meter