Parallel Control Valves Regulating Pressure

Hi everyone,
I need to control 2 identical parallel control valves to regulate the downstream (for which also 3 pressure transmitters have been considered) . in case I use one PID or 2 PIDs with identical parameters what would be the outcome? Each valve can handle 100% of flow and I use the median value of the PTs.
BR

Nastaari
 
Since each valve can supply 100% of the required flow then I would just use one valve at a time.
What is the fluid?
The pressure will change a function of the net flow in or out.
dPressure/dTime = BulkModulusOfFluid*(FlowIn(t)-FlowOut(t))/VolumeOfFluidUnderPressure
Control will be easier if you know the rate the fluid is flowing out. Hopefully the fluid flowing out will not change rapidly.
If the fluid flowing out can be measured accurately then this information can be used as a feed forward or bias for the PID control.

Why were two valves installed? Redundancy?
 
Since each valve can supply 100% of the required flow then I would just use one valve at a time.
What is the fluid?
The pressure will change a function of the net flow in or out.
dPressure/dTime = BulkModulusOfFluid*(FlowIn(t)-FlowOut(t))/VolumeOfFluidUnderPressure
Control will be easier if you know the rate the fluid is flowing out. Hopefully the fluid flowing out will not change rapidly.
If the fluid flowing out can be measured accurately then this information can be used as a feed forward or bias for the PID control.

Why were two valves installed? Redundancy?

Thanks for your explanations . The fluid is HP steam.
Would you please help me understand how I can use only one valve at a time because in this case I need to set one as Duty and the other as stand-by and because the regulating valve is not like pump or shut off valve (which can have a faulty status feedback), I do not see how to change over from one to the other valve.
BR
 
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