What is one of the main purposes of a tag number?

A tag number primarily serves as a unique identifier for each instrument or control device within a facility. By identifying the control device information, the tag number helps in organizing, referencing, and managing various instruments efficiently. This identification is crucial in maintenance, troubleshooting, and operational procedures, as it allows personnel to quickly locate necessary documentation, such as wiring diagrams, calibration certificates, and operational manuals associated with that specific instrument.

While classifying an instrument's design, providing control system access, or measuring environmental conditions may involve using a tag number in some contexts, they do not capture the principal purpose of a tag number, which focuses on identification. Tag numbers are essential for systematizing instruments to ensure safety and operational efficacy within industrial environments.