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ISA and Labeling Philosophy

ISA and Labeling Philosophy

ISA and Labeling Philosophy

Our company designs small wastewater treatment plants. Just a few technical people, but we also work with contractors and vendors, sharing drawings including P&IDs. A vendor is pushing us to use ISA standards in our P&IDs, but our controls engineer is also in charge of training and oversight of operators, and prefers more intuitive labels. DOxxx for a dissolved oxygen sensor, PHxxx for a pH sensor, etc. Is there an alternate naming convention that matches this more intuitive style, or would we be completely on our own if we got away from calling a turbidity meter an AIT? As you might guess, none of us have much experience with ISA.

Thanks for your thoughts.

RE: ISA and Labeling Philosophy

For me, it's a question of writing for your audience.

If the operators constantly refer to the diagrams then aren't they the primary audience?

Is it likely that anyone conversant in ISA symbology that will falter and choke if encountering DOxxx or PHxxx?

If it were me, I'd stick with what you've been doing for the reason you cited, "controls engineer is also in charge of training and oversight of operators, and prefers more intuitive labels". It doesn't bother him and it helps the operators understand what's going on.

RE: ISA and Labeling Philosophy

Being more operator than anything else, I have to agree with danw2; a motto I've learned [the hard way!] to adopt over the years resembles that of the US marines: "Simpli Fy."

In my experience, operators are a practical lot and gravitate toward the use of operating nomenclature in the performance of their duties. They prefer to stick to the essentials, and wherever possible tend to avoid the unnecessary inclusion of complicating factors. This trait contributes much toward keeping a clear head when stressful situations develop [and they will].

Of particular note is the common practice of utilizing custom-made operating diagrams, particularly when preparing isolations and/or establishing work protection. The use of 'intuitive' nomenclature aids greatly in this regard.

Engineers and Protection & Control / Electrical & Instrumentation personnel, on the other hand, typically employ control and wiring diagrams which bear both engineering and operating designations; the additional information is of great assistance in troubleshooting systems and diagnosing problems.

Hope this helps.


"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: ISA and Labeling Philosophy

I use the ISA standard AIT, but then use a tag such as pH outside of the bubble symbol to show the analysis that is being performed, as directed by the 2009 ANSI/ISA 5.1 standard in 4.2(3):


Measured/Initiating Variable analysis [A] shall be used for all types of process stream composition and physical property analysis. The type of analyzer, and for stream component analyzers, the components of interest, shall be defined outside the tagging bubble.

I think using custom tagging does a disservice to your company. Remember, there is a much wider audience for your drawings than just your company employees and controls engineer. You mentioned contractors, vendors, and operators, but there could also be other clients, third-party engineering firms, government agencies, inspectors, etc. It is for this reason that the standard has been developed - so we can speak a common graphical language. If I saw your system drawings without ISA tagging, I would have to take extra time to interpret them, I'd probably be a little annoyed, and I'd have less respect for the engineers at the company who developed the system drawings. If I was performing a bid evaluation where your company was bidding against other vendors who used ISA tagging, I'd count it against your company, as it makes it look like you don't know what you're doing. (I did this not too long ago when a general contractor put in a bid using CSI Masterformat spec numbers that were outdated, and I pointed it out to the bid evaluation committee. That contractor didn't get awarded the contract. Part of the reason was that they appeared out of touch with current standards.) Also, if an operator trained by your engineer gets a new job where ISA tagging is used, they're certain to be confused for a while while they learn the standard nomenclature. It just seems less than professional to me to not use the ANSI standard for tagging since it addresses chance of confusion by requiring the definition of the component outside the bubble.

"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
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