I received a call today from a DeltaV customer who was looking to see if anyone had a control strategies to deal with pressure spikes causing DP measurement alarms in their system. I said I'd pose it to the DeltaV community. I unfortunately didn't get any more detail on if it is a gas or liquid being measured.
I was in a meeting with Greg McMillan and bounced the question off him. He provided a couple of ideas, plus a copy of his presentation for the upcoming Emerson Exchange conference in Anaheim.
He first suggested that if possible, resolve the source of pressure pulses. Sometimes improper tuning contributes to these pulses. Next, it you can measure the source and have enough time to react to the disturbance, feedforward control can be applied.
If the first two cases don't apply, the he suggests using a deadtime block to calculate the rate of change of the pressure (PVnew -PVold). When a large change in PV is measured, change the controller mode to output tracking and open the downstream valve enough for a period of 1 reset time (per the integral action of the loop). After this time, release the loop back to feedback control.
The open loop backup to deal with incredibly fast unmeasured disturbances in on slides 32-37. Also see slides 25-28 on feedforward in his presentation.
If anyone has clarifying questions or other suggestions, please share!
Nice hints from a real guru, I would say if it's a simple loop just tune for least overshoot
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