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P&ID symbol for VFD (VSD)

P&ID symbol for VFD (VSD)

P&ID symbol for VFD (VSD)

I've seen two methods for showing a variable speed drive for motors on P&IDs.

One is a standard instrument bubble with SIC inside, with a doted line going to the motor/pump.

The other is a positioner, commonly used for control valves, which 'indicates' an actuator, attached to the motor/pump.

To me, the positioner indicates that the speed control is pneumatic somehow, even if only an electrical line is drawn to it.

Is there a standard out there?

This is normally the space where people post something insightful.

RE: P&ID symbol for VFD (VSD)

My preference is the SIC and SC instrument bubble.

I have also seen the positioner symbology used for non pneumatic control, usually on louvers, vents, etc. where it is an elec motor doing the opening/closing.

In my experience, the P&ID bubbles/symbology "standard" usually vary by projects/clients. And from your statement "I've seen two methods for showing a variable speed drive for motors on P&IDs.", it seems that this is also your experience.
From what I see in my industry, in my part of the world, is that ISA is a starting point, perhaps a guiding document. I see lots of "BPV" for a Back Pressure Control Valve where if one followed ISA, it would probably be PV (Pressure Valve) or PCV (Pressure Control Valve).

Other responders have stated that ISA should "be the" standard. IMHO, I find that the ISA standard is not prescriptive - it leaves a fair bit of leeway for the user to make it work for their particular needs.

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