Tagged: #Cascade #PIDE
- This topic has 3 replies, 2 voices, and was last updated 5 days, 12 hours ago by Thomas Damon.
- November 19, 2022 at 10:04 am #20785khyap96ParticipantKarma: 16Rank: Padawan
For my project, I need to control a flow control valve (FCV). Where a pressure transmitter is located before FCV to check pressure and a flow transmitter is located after FCV to check flow rate. You may refer attachment for clearer image.
I believe this is a cascade control where,
- Pressure is first checked. If pressure ? 8.5 barg, the FCV is controlled by pressure. If pressure ? 8.0 barg, FCV will be totally closed. (Pressure setpoint at 8.5 barg)
- Else, it is controlled by flow. (Flow setpoint at 140Sm3/h)
I have started a draft of the Cascade PIDE, as attached. But I think something is wrong because it fails when I try to simulate using Logix Emulate. Can anyone please advise or help?
Attachments:You must be logged in to view attached files.November 19, 2022 at 5:35 pm #20788Thomas DamonParticipantKarma: 46Rank: Padawan
That is not a case for PIDE cascade control, you would use cascade control if the output of the first PIDE is the setpoint for the next. You need 2 seperate PIDE’s with a low select going to the valve.November 20, 2022 at 9:40 pm #20791khyap96ParticipantKarma: 16Rank: Padawan
Thank you for your advise! Did you mean this should be a multiloop control, scheme on page 7 as attached in pdf file?
Also i have attached a draft of a multiloop PIDE.
Attachments:You must be logged in to view attached files.November 24, 2022 at 12:34 am #20796Thomas DamonParticipantKarma: 46Rank: Padawan
Yes, the 2 loops interact as per page 7 with it set for low select. Make sure to bring the output of the select block back to the CV Previous of both PIDE’s so the non- controlling one stays active and doesn’t windup.
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