ISA 5.3

This standard satisfies the requirements for symbolicallyrepresenting the functions of distributed ControVshared displayinstrumentation, logic, and computer systems. The instrumentationis generally composed of field hardware communication networks andcontrol room operator devices. This standard is applicable to allindustries using process control and instrumentation systems.

No effort will be made on the flow diagram to explain theinternal construction, configuration, or method of operation ofthis type of instrumentation, logic and computer systems. Personnelneeding to understand flow diagrams must have a basic understandingof the total system in order to correctly interpret the diagram.The type of computation or the use of the process variable within aprogram is not indicated except in those cases where the processvariable is an integral part of the control strategy. Inapplications where all instrument system data base information isavailable to the computer via the communication link, the depictionof the computer interconnections is optional in order to conservespace on flow diagrams.

Application to work activities

This standard is intended for use whenever any reference to aninstrument is required. Such references may be required for thefollowing 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.

Relationship to other ISA standards

This standard complements ISA-S5.1, “Instrumentation Symbols andIdentification,” for symbols and formats representing functionalidentification codes. For clarification of examples, a limitedamount of ISA-S5.1 symbology has been included in thisdocument.

Relationship to other standards

Where applicable, definitions not included in Section 3 are inaccordance with ANSI X3/TR-1-77, “American National Dictionary forInformation Processing,” and/or ISA-S5.1.

Purpose

The purpose of this standard is to establish documentation forthat class of instrumentation consisting of computers, programmablecontrollers, minicomputers and micro-processor based systems thathave shared control, shared display or other interface features.Symbols are provided for interfacing field instrumentation, controlroom instrumentation and other hardware to the above. Terminologyis defined in the broadest generic form to describe the variouscategories of these devices.

It is not the intent of this standard to mandate the use of eachtype symbol for each occurrence of a generic device within theoverall control system. Such usage could result in undue complexityin the case of a Piping and Instrument Drawing (P&ID). If, forexample, a computer component is an integral part of a distributedcontrol system, the use of the computer symbol would normally be anundesirable redundancy. If, however, a separate general purposecomputer is interfaced with the system, the inclusion of thecomputer symbol may provide the degree of clarity needed forcontrol system understanding.

This standard attempts to provide the users with definedsymbolism and rules for usage, which may be applied as needed toprovide sufficient clarity of intent. The extent to which thesesymbols are applied to various types of drawings remains with theusers. The symbols may be as simple or complex as needed to definethe process.

Edition:

83

Published:

01/01/1983

Number of Pages:

22

File Size:

1 file , 1.4 MB