ISA 5.3 : 1983

1 Purpose
2 Scope
  2.1 Application to work activities
  2.2 Relationship to other ISA standards
  2.3 Relationship to other standards
3 Definitions and abbreviations
4 Symbols
  4.1 General
  4.2 Distributed control/shared display symbols
  4.3 Computer symbols
  4.4 Logic and sequential control symbols
  4.5 Internal system function symbols
  4.6 Common symbols
  4.7 Recorders and other historical data retention
5 Identification
  5.1 Software alarms
  5.2 Contiguity of symbols
6 Alarms
  6.1 General
  6.2 Instrument system alarms
Appendix A - Examples

This standard satisfies the requirements for symbolically representing the functions of distributed control/shared display instrumentation, logic, and computer systems. The instrumentation is generally composed of field hardware communication networks and control room operator devices. This standard is applicable to all industries using process control and instrumentation systems. No effort will be made on the flow diagram to explain the internal construction, configuration, or method of operation of this type of instrumentation, logic and computer systems. Personnel needing to understand flow diagrams must have a basic understanding of the total system in order to correctly interpret the diagram. The type of computation or the use of the process variable within a program is not indicated except in those cases where the process variable is an integral part of the control strategy. In applications where all instrument system data base information is available to the computer via the communication link, the depiction of the computer interconnections is optional in order to conserve space on flow diagrams. This standard is intended for use whenever any reference to an instrument is required. Such references may be required for the following uses as well as others: Flow diagrams, process and mechanical; Instrumentation system diagrams; Specifications, purchase orders, manifests, and other lists; Construction drawings; Technical papers, literature, and discussions; Tagging of instruments; and Installation, operation, and maintenance instructions, drawings, and records. This standard complements ANSI/ISA-5.1-1984 (R1992), Instrumentation Symbols and Identification, for symbols and formats representing functional identification codes. For clarification of examples, a limited amount of ANSI/ISA-5.1-1984 (R1992) has been included in this document. Where applicable, definitions not included in Section 3 are in accordance with ANSI X3/TR-1-77, ‘American National Dictionary for Information Processing,’ and/or ANSI/ISA-5.1-1984 (R1992).