Hi all, i'm after some help on a flow control valve control strategy. There are 8 parallel vessels that require evenly distributed flow.
Each vessel features a flow control valve on the inlet, and a flow transmitter on the outlet.
Currently the algorithm is:
1. Add all vessel_flow values and divide by number of vessels = vessel required_flow.
2. Individual vessel_flow - required_flow = diff_flow
3. Each control valve has a PID controller that will modulate the valve position to set diff_flow to zero.
This initially works well and will balance diff_flow within 0.1L/.s. (Total flow upto 200 L/s).
This issue occurs after the the most restrictive vessel changes, all valves will readjust and bring diff_flow back within spec. However, now none of the valves are at their maximum value, introducing further resistance on the system.
I need a way to bias the balancing valves so they are all trying to open further (while none are at maximum value), while also maintaining balanced a flow.
I'm thinking a periodic addition to all valves, or a cascaded loop that will try to increase "average valve position" etc
Any ideas, comments, links, videos or thoughts would be awesome!
Each vessel features a flow control valve on the inlet, and a flow transmitter on the outlet.
Currently the algorithm is:
1. Add all vessel_flow values and divide by number of vessels = vessel required_flow.
2. Individual vessel_flow - required_flow = diff_flow
3. Each control valve has a PID controller that will modulate the valve position to set diff_flow to zero.
This initially works well and will balance diff_flow within 0.1L/.s. (Total flow upto 200 L/s).
This issue occurs after the the most restrictive vessel changes, all valves will readjust and bring diff_flow back within spec. However, now none of the valves are at their maximum value, introducing further resistance on the system.
I need a way to bias the balancing valves so they are all trying to open further (while none are at maximum value), while also maintaining balanced a flow.
I'm thinking a periodic addition to all valves, or a cascaded loop that will try to increase "average valve position" etc
Any ideas, comments, links, videos or thoughts would be awesome!