5.1
ISA-5.1-1984 (R1992) Instrumentation Symbols and Identification
General reference, softbound, 72pp.
$105.00

Establishes a uniform means of designating instruments and instrumentation systems used for measurement and control. The different needs of various organizations are recognized (where not inconsistent with the objectives of the standard) by providing alternative symbolism methods. A number of options are provided for adding information or simplifying the symbolism, if desired. Includes additional information on symbolism for function blocks, function designations, computer functions, and programmable logic control.

Scope:
The procedural needs of various users are different. The standard recognizes these needs, when they are consistent with the objectives of the standard, by providing alternative symbolism methods. A number of examples are provided for adding information or simplifying the symbolism, as desired.

Process equipment symbols are not part of this standard, but are included only to illustrate applications of instrumentation symbols.

The standard is suitable for use in the chemical, petroleum, power generation, air conditioning, metal refining, and numerous other, process industries.

Certain fields, such as astronomy, navigation, and medicine, use very specialized instruments that are different from the conventional industrial process instruments. No specific effort was made to have the standard meet the requirements of those fields. However, it is expected that the standard will be flexible enough to meet many of the needs of special fields.

The standard is suitable for use whenever any reference to an instrument or to a control system function is required for the purposes of symbolization and identification. Such references may be required for the following uses, as well as others:

• Design sketches
• Teaching examples
• Technical papers, literature, and discussions
• Instrumentation system diagrams, loop diagrams, logic diagrams
• Functional descriptions
• Flow diagrams: Process, Mechanical, Engineering, Systems, Piping (Process) and Instrumentation
• Construction drawings
• Specifications, purchase orders, manifests, and other lists
• Identification (tagging) of instruments and control functions
• Installation, operating and maintenance instructions, drawings, and records

The standard is intended to provide sufficient information to enable anyone reviewing any document depicting process measurement and control (who has a reasonable amount of process knowledge) to understand the means of measurement and control of the process. The detailed knowledge of a specialist in instrumentation is not a prerequisite to this understanding.

The symbolism and identification methods provided in this standard are applicable to all classes of process measurement and control instrumentation. They can be used not only to describe discrete instruments and their functions, but also to describe the analogous functions of systems which are variously termed "shared display," "shared control," "distributed control," and "computer control."

The standard provides for the identification and symbolization of the key functions of an instrument. Additional details of the instrument are better described in a suitable specification, data sheet, or other document intended for those requiring such details.

The standard covers the identification of an instrument and all other instruments or control functions associated with it in a loop. The user is free to apply additional identification — by serial number, unit number, area number, plant number, or by other means.

Purpose:
The purpose of this standard is to establish a uniform means of designating instruments and instrumentation systems used for measurement and control. To this end, a designation system that includes symbols and an identification code is presented.