Scope
Symbols are included to depict mathematical functions, graphs, process equipment, instruments, and electrical equipment. The symbols are suitable for use in dynamic displays, as on cathode-ray tubes (CRT's), and static displays, such as graphic panels. Though the standard may make use of standard symbols now used for piping and instrument diagrams, logic diagrams, loop diagrams, mathematical works, and other documents, it is generally expected to be used in ways to complement the use of existing types of engineering documents.
The symbolism is intended to be independent of type or brand of hardware or computer software. Strong liaison shall be maintained with the ISA5.1, ISA5.2, ISA5.3, and ISA5.4 committees.
Purpose
The purpose of this standard is to establish a system of graphic symbols for displays that are used by plant operators for process measurement and control. The system is intended to promote (a) the fullest and quickest comprehension by the operators of the information that is to be conveyed through the displays, and (b) uniformity of practice throughout the process industries.
Resulting benefits are intended to be (a) a decrease of operator errors, (b) a shortening of operator training, and (c) generally better and easier matching of the information-transmission intent of control system designers with the reception and interpretation of results by plant operators.
The standard is suitable for use in the chemical, petroleum, power generation, air conditioning, metal refining, and numerous other industries.
ISA5.5 no longer is an active subcommittee. The standard it produced, ISA-5.5-1985, Graphic Symbols for Process Displays, is not current with today's process display technology. However, based on a review of the document by ISA5, it appears to be of some continuing use to those whose process displays were established in, say, the mid-to-late 1980s.
For more information, please contact Charley Robinson, ISA Standards.