Originally published in 1984. As told by Tom McAvinew.
The use of ISA-5.1, Instrumentation Symbols and Identification, originally published in 1984, is in general quite widespread. That is because it is important to consistently identify instrumentation in project documents used for specifying, purchasing, tracking, installing, and eventually maintaining them.
Although often cited on project or site documents along with other standards, ISA-5.1 is often not followed completely—particularly regarding device identification tagging. Sometimes this is because a particular site may not have followed the standard in the past. Other times, operations personnel on a project may insist on using more phonetic tagging, rather than one of the basic tenets of ISA-5.1—that ID tagging be based on primary variable functional tagging.
My role with ISA-5.1 has been as a resource, based on my 50+ years of experience in the application of the standard for both operating and engineering design firms. None of this would have been possible without the tutelage of Marvin D. Weiss, one of the pioneers in process analytical instrumentation, who met a fresh-out-of-school chemical engineer with an interest in instrumentation and process control, then convinced him to join ISA in 1964.