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Does anyone know what these three symbols are? I am working to identify them but they do not seem to appear in the site: https://www.edrawsoft.com/pid-legend.php

Does anyone know a better reference for P&ID diagram symbols?

Sample from a project I am working on

Cameron Wight
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1 Answers1

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Two of those are not standard usage symbols in that way. You may to have to use context and/or a physical inspection to determine what they are. Where is that diagram from?

Various organizations define symbols for piping and/or control. The International Society of Automation uses ANSI/ISA-5.1-2009, which you can officially find on their website.


  1. The top symbol is probably meant to be a shut-off valve, probably ball type. The usual symbol is something like:
    ball valve

  2. The middle symbol is a fairly standard Solenoid-controlled valve.

  3. The bottom symbol could be meant to be a butterfly valve (for flow control), or a "blowout" valve / rupture disk (for over-pressure safety).
    The standard symbols for those are like:
    butterfly valve and pressure or enter image description here

Brock Adams
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  • I did not know in these drawings that it was a common practice to use non-standard symbols. I was hoping that someone could point me towards a standard list of P&ID symbols, however, if it is common that designers use non-standard symbols that definately leaves more of these drawings up to interpretation that I am used to from an electrical system in the aircraft industry. Thank you for your reply, I will try and determine from the context of the drawing what the meaning of the symbols are? Cheers – Cameron Wight May 31 '19 at 15:31
  • Good luck. and let us know what you find. Unless you are dealing with a (big) government or a (big) company, there are no symbol police and newbies often just pic the most convenient graphic from their template/app that seems to work. – Brock Adams May 31 '19 at 15:38