ISA 5.1

This standard establishes a uniform means of depicting and identifying instruments or devices and their inherent functions, instrumentation systems and functions, and application software functions used for measurement, monitoring, and control, by presenting a designation system that includes identification schemes and graphic symbols.

General

This standard is intended to meet the different procedures of various users who need to identify and graphically depict measurement and control equipment and systems. These differences are recognized when they are consistent with the objectives of this standard, by providing alternative symbols and identification methods.

This document provides graphic symbols for representations of the instrumentation and control functions required for process or equipment measurement, indication, and control of variables used in any of the following applications.

a) Instrumentation and control diagrams, which illustrate and identify instruments and related devices and their inherent functions, instrumentation systems and functions, and application software functions used for measurement, monitoring, and control. These illustrations can appear as part of process flow diagrams (PFDs) and piping and instrumentation diagrams (P&IDs), which include process equipment, mechanical equipment, and piping information.

b) Functional diagrams, which depict application software functions (analog and binary signal processing) for implementation into the selected control systems.

c) Binary logic diagrams, which depict interlocking and stepwise logic programming.

d) Electrical schematics, which depict electrical circuitry for on-off control. These include ladder diagrams.

e) Instrument loop diagrams, which depict a composite representation of instrument loop information, containing associated electrical, piping, and process equipment connections as well as other pertinent information, including ranges, alarms, and device configuration settings.

Examples of identification and symbol applications are available in associated technical reports ISA-TR5.1.02, Instrumentation and Control Identification System Guidelines and ISA-TR5.1.03, Instrumentation and Control Graphic Symbols Guidelines and are intended to illustrate basic concepts in the construction of the identification systems and diagrams covered by this standard that are applicable to all industries.