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P&ID Symbology

P&ID Symbology

P&ID Symbology

I have been in the equipment industry (compressors mainly) for the past 11 years.  I have seen more combinations of symbols used on P&ID that I really care to.  However, I have been asked to write a company standard.  I sort of thought that ISA-5 would contain everything that I needed to know.  For instruments, this is the case.  However, for Valves, process lines, hoses & such, ISA leaves this stuff out or only addresses a few types.  Does anyone know of another ISA standard for these? Any other standard such as API, ASME, ANSI, etc would also work to.

Chris Foley
Midland, TX

RE: P&ID Symbology

Please clarify the process or industry as equipment varies for the polymer business and the oil patch business.  The P&ID equipment symbols are often similar within an industry.  However, I don't know of a standard as such.  The site that dbaird linked may be useful.  It launched AutoCAD and many engineers don't have ACAD.

Some of the HMI software consulting houses have symbol libraries for Wonderware, etc.  In fact, these may be generated to look somewhat like the equipment.

Consider finding legend sheets from the operating company or other contractors for that facility and generate similar symbols.


RE: P&ID Symbology

Thanks for the input guys.  This lack of standards is the problem.  We are constantly spending valuable designers time redoing P&IDs to match every customers whim.  This is not a fiscally sound approach.  David's link is similar to many others that I have found (although it is HUGE!!!).  I can show a certian control valve 10 different ways.  ISA-5 is the accepted standard but it does a very poor job for valves (only has 3 symbols for all valve types when we need around 8).  It does have a section for process symbols in ISA 5.5 but this is for HMI interface screens.  At this point, I think I am going to have to do everything by ISA-5 that I can and suppliment that with a company standard.  That is, of course, unless someone else knows an API style standard that will help.


RE: P&ID Symbology

Thats the problem with P&ID's, every company has their own standard, not only for symbols but for instrument tagging, line numbering, issue numbering, fonts, line thickness and even what should and should not be shown.
In your case I would suggest that when you quote you price for your own standard P&ID style and then charge extra if the client wants their own standards applied.

RE: P&ID Symbology

Francis, I agree as I have tried that approach in the past also.  It is very diffcult to get the sales force in line with this.  They like to give it away to "get the order."  They do not understand that the extra work and possible errors in engineering are worth $$$.  Even if you discount this approach, the confusion that the shop floor faces is extreme.  If you are forced to create a "special" P&ID for the customer, then you have to maintain a second type (the company standard) for the shop floor.  This just makes the whole situatoin worse.

RE: P&ID Symbology

I think that the University of Texas participated in the preparation of Process Industry Practices that address some of the issues including piping line designations, etc.


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