Instrument Loop tags for Pressure Control loop with Variable speed pump motor as final element

[Tonya L]

Reference thread196-141426

I need to assign tags for a pressure control loop using a VFD for the final element. We have a PT for the input and a PIC DCS control tag but I'm not sure what to use for the final element tag. I know that its typically client preference but thought I'd ask for opinions.

 

[controlnovice]

Wow...I was the originator of that question many years ago.

I now lean toward the PIC bubble linked to an Instrument Bubble with SC in it, which represents the VFD. The SC bubble is linked to the pump symbol (Or motor symbol if it's there).

I've also used the PIC bubble linked to a box with VFD written in it, which is then tied to the pump/motor...based on customer's previous designs.

If you use the SC bubble, it's helpful to write "VFD" text next to the bubble for clarity.



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