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AMERICAN NATIONAL STANDARD

ANSI/ISA–5.1–1984 (R1992)
Formerly ANSI/ISA–S5.1–1984 (R1992)

Instrumentation Symbols
and Identification

NOTICE OF COPYRIGHT
This is a copyrighted document and may not be copied or distributed in any
form or manner without the permission of ISA. This copy of the document was
made for the sole use of the person to whom ISA provided it and is subject to
therestrictions stated in ISA’s license to that person. It may not be provided to
any other person in print, electronic, or any other form. Violations of ISA’s
copyright will be prosecuted to the fullest extent of the law and may result in
substantial civil and criminal penalties.

Reaffirmed 13 July 1992
TM

ISA–The Instrumentation,
Systems, and
Automation Society

ANSI/ISA-5.1-1984(R1992), Instrumentation Symbols and Identification
ISBN 0-87664-844-8
Copyright ã 1984 by the Instrument Society of America. All rights reserved. Printed in the United
States of America. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means (electronic, mechanical, photocopying, recording, or
otherwise), without the priorwritten permission of the publisher.
ISA
67 Alexander Drive
P.O. Box 12277
Research Triangle Park, North Carolina 27709

Preface

This preface is included for information and is not a part of ANSI/ISA-5.1-1984 (R1992).
This standard has been prepared as part of the service of ISA toward a goal of uniformity in the
field of instrumentation. To be of real value, this document should not bestatic, but should be
subject to periodic review. Toward this end, the Society welcomes all comments and criticisms,
and asks that they be addressed to the Secretary, Standards and Practices Board, ISA, 67
Alexander Drive, P.O. Box 12277, Research Triangle Park, NC 27709, Telephone (919) 5498411, e-mail: standards@isa.org.
The ISA Standards and Practices Department is aware of the growing need forattention to the
metric system of units in general, and the International System of Units (SI) in particular, in the
preparation of instrumentation standards. The Department is further aware of the benefits to
U.S.A. users of ISA standards of incorporating suitable references to the SI (and the metric
system) in their business and professional dealings with other countries. Toward this end,this
Department will endeavor to introduce SI-acceptable metric units in all new and revised
standards to the greatest extent possible. The Metric Practice Guide, which has been published
by the Institute of Electrical and Electronics Engineers as ANSI/IEEE Std. 268-1982, and future
revisions will be the reference guide for definitions, symbols, abbreviations, and conversion
factors.
It isthe policy of ISA to encourage and welcome the participation of all concerned individuals and
interests in the development of ISA standards. Participation in the ISA standards-making
process by an individual in no way constitutes endorsement by the employer of that individual, of
ISA, or of any of the standards that ISA develops.
The information contained in the preface, footnotes, andappendices is included for information
only and is not a part of the standard.
The instrumentation symbolism and identification techniques described in the standard
accommodate the advances in technology and reflect the collective industrial experience gained
since the publication of Recommended Practice RP5.1 in 1949.
This revision attempts to strengthen the standard in its role as a tool ofcommunication in the
process industries. Communication presupposes a common language; or, at the very least, it is
facilitated by one. The standard offers the foundation for that common language.
When integrated into a system, the symbols and designations presented here form a concise,
dedicated language which communicates concepts, facts, intent, instructions, and knowledge
about measurement and...