RECOMMENDED PRACTICE
ANSI/ISA-RP12.06.01-2003
Formerly ANSI/ISA-RP12.06.01-1995 (R2002)
Recommended Practice for
Wiring Methods for
Hazardous (Classified)
Locations Instrumentation
Part 1: Intrinsic Safety
Approved 16 April 2003
TM
ISA–The Instrumentation,
Systems, and
Automation Society
This is a preview. Click here to purchase the full publication.
Sure! Here are four ways in which a row of barriers can be connected to the I.S. (Intrinsic Safety) ground:
Direct Connection to Ground Electrode: Each barrier can be directly connected to a separate grounding electrode. This
ensures a high integrity, low-resistance return path for fault currents 1 2.
Common Ground Bus: Barriers can be connected to a common ground bus, which is then connected to the grounding
electrode. This method helps in maintaining a uniform ground potential 1.
Shielded Cable: Using shielded cables to connect barriers to the ground can help in minimizing electromagnetic
interference and ensuring a stable ground connection 2.
Metal Enclosure Grounding: If the barriers are housed in a metal enclosure, the enclosure itself can be grounded. This
provides an additional layer of protection and ensures that the entire system is at the same ground potential 3.
Sure! Here are the definitions for the terms used in conjunction with zener safety barriers:
End to End Resistance: This is the total resistance measured across the barrier from one end to the other. It includes the
resistance of all components within the barrier, such as the zener diodes and series resistors 1.
Fuse Rating: The fuse rating indicates the maximum current the fuse can handle before it blows. In zener barriers, the fuse
protects the zener diodes from excessive current, ensuring the circuit remains safe 2.
Maximum Voltage in the I.S. Circuit: This is the highest voltage that can appear across the intrinsically safe connections of
the associated apparatus under fault conditions. It is crucial for ensuring that the voltage does not exceed safe limits 3.
Maximum Current in the I.S. Circuit: This refers to the maximum current that can be drawn from the intrinsically safe
connections of the associated apparatus under fault conditions. It ensures that the current remains within safe limits to
prevent ignition in hazardous areas 4.
ANSI/ISA-RP12.06.01-2003
Recommended Practice for Wiring Methods for Hazardous (Classified) Locations Instrumentation Part 1:
Intrinsic Safety
ISBN: 1-55617-865-4
Copyright © 2003 by ISA —The Instrumentation, Systems, and Automation Society. All rights reserved.
Not for resale. 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 prior written permission of the Publisher.
ISA
67 Alexander Drive
P.O. Box 12277
Research Triangle Park, North Carolina 27709
This is a preview. Click here to purchase the full publication.
—3—
ANSI/ISA-RP12.06.01-2003
Preface
This preface, as well as all footnotes and annexes, is included for information purposes and is not part of
ANSI/ISA-RP12.06.01-2003.
This document has been prepared as part of the service of ISAthe Instrumentation, Systems, and
Automation Societytoward a goal of uniformity in the field of instrumentation. To be of real value, this
document should not be static 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) 549-8411; Fax (919) 549-8288; E-mail: standards@isa.org.
The ISA Standards and Practices Department is aware of the growing need for attention 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 USA 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, recommended practices, and technical
reports to the greatest extent possible. Standard for Use of the International System of Units (SI): The
Modern Metric System, published by the American Society for Testing & Materials as IEEE/ASTM SI 1097, and future revisions, will be the reference guide for definitions, symbols, abbreviations, and
conversion factors.
It is the policy of ISA to encourage and welcome the participation of all concerned individuals and
interests in the development of ISA standards, recommended practices, and technical reports.
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, recommended practices, and technical
reports that ISA develops.
CAUTION — ISA ADHERES TO THE POLICY OF THE AMERICAN NATIONAL STANDARDS
INSTITUTE WITH REGARD TO PATENTS. IF ISA IS INFORMED OF AN EXISTING PATENT THAT IS
REQUIRED FOR USE OF THE DOCUMENT, IT WILL REQUIRE THE OWNER OF THE PATENT TO
EITHER GRANT A ROYALTY-FREE LICENSE FOR USE OF THE PATENT BY USERS COMPLYING
WITH THE DOCUMENT OR A LICENSE ON REASONABLE TERMS AND CONDITIONS THAT ARE
FREE FROM UNFAIR DISCRIMINATION.
EVEN IF ISA IS UNAWARE OF ANY PATENT COVERING THIS DOCUMENT, THE USER IS
CAUTIONED THAT IMPLEMENTATION OF THE DOCUMENT MAY REQUIRE USE OF TECHNIQUES,
PROCESSES, OR MATERIALS COVERED BY PATENT RIGHTS. ISA TAKES NO POSITION ON THE
EXISTENCE OR VALIDITY OF ANY PATENT RIGHTS THAT MAY BE INVOLVED IN IMPLEMENTING
THE DOCUMENT. ISA IS NOT RESPONSIBLE FOR IDENTIFYING ALL PATENTS THAT MAY
REQUIRE A LICENSE BEFORE IMPLEMENTATION OF THE DOCUMENT OR FOR INVESTIGATING
THE VALIDITY OR SCOPE OF ANY PATENTS BROUGHT TO ITS ATTENTION. THE USER SHOULD
CAREFULLY INVESTIGATE RELEVANT PATENTS BEFORE USING THE DOCUMENT FOR THE
USER’S INTENDED APPLICATION.
HOWEVER, ISA ASKS THAT ANYONE REVIEWING THIS DOCUMENT WHO IS AWARE OF ANY
PATENTS THAT MAY IMPACT IMPLEMENTATION OF THE DOCUMENT NOTIFY THE ISA
STANDARDS AND PRACTICES DEPARTMENT OF THE PATENT AND ITS OWNER.
ADDITIONALLY, THE USE OF THIS DOCUMENT MAY INVOLVE HAZARDOUS MATERIALS,
OPERATIONS OR EQUIPMENT. THE DOCUMENT CANNOT ANTICIPATE ALL POSSIBLE
APPLICATIONS OR ADDRESS ALL POSSIBLE SAFETY ISSUES ASSOCIATED WITH USE IN
HAZARDOUS CONDITIONS. THE USER OF THIS DOCUMENT MUST EXERCISE SOUND
PROFESSIONAL JUDGMENT CONCERNING ITS USE AND APPLICABILITY UNDER THE USER’S
Copyright 2003 ISA. All rights reserved.
This is a preview. Click here to purchase the full publication.
ANSI/ISA-RP12.06.01-2003
—4—
PARTICULAR CIRCUMSTANCES. THE USER MUST ALSO CONSIDER THE APPLICABILITY OF
ANY GOVERNMENTAL REGULATORY LIMITATIONS AND ESTABLISHED SAFETY AND HEALTH
PRACTICES BEFORE IMPLEMENTING THIS DOCUMENT.
THE USER OF THIS DOCUMENT SHOULD BE AWARE THAT THIS DOCUMENT MAY BE IMPACTED
BY ELECTRONIC SECURITY ISSUES. THE COMMITTEE HAS NOT YET ADDRESSED THE
POTENTIAL ISSUES IN THIS VERSION.
The following people served as voting members of ISA Subcommittee SP12.6:
NAME
COMPANY
D. Bishop, Managing Director
R. Masek, Chair
N. Abbatiello
R. Allen
W. Bennett
K. Boegli
C. Bombria
J. Bossert
R. Cardinal
A. Engler
T. Feindel
W. Fiske
L Goettsche
B. Larson
J. Miller
A. Mobley
O. Murphy
E. Olson
J. Oudar
A. Page
B. Schaefer
P. Schimmoeller
T. Schnaare
D. Wechsler
C. Wellman
Consultant
CSA International
Eastman Kodak Co.
Honeywell Inc.
Pepperl + Fuchs Inc.
Phoenix Contact Inc.
Consultant
Hazloc Inc.
Bently Nevada LLC
EGS Electrical Group
R. Stahl Inc.
Intertek Testing Services
Consultant
Turck Inc.
Detector Electronics Corp.
3M Co.
Brooks Instruments
Ellis Engineering Co.
ExLoc Corp.
MSHA Approval & Certification Center
Underwriters Laboratories Inc.
CSA International
Rosemount Inc.
Dow Chemical Co.
DuPont Engineering
The following people served as voting members of ISA Committee SP12:
NAME
COMPANY
T. Schnaare, Chair
W. Lawrence, Vice Chair
D. Bishop, Managing Director
N. Abbatiello
D. Ankele
B. Apel
A. Ballard
W. Bennett
K. Boegli
R. Brodin
R. Buschart
R. Cardinal
C. Casso
M. Coppler
J. Cospolich
Rosemount Inc.
FM Approvals
Consultant
Eastman Kodak Company
Underwriters Laboratories Inc.
MSA Instrument
Crouse Hinds Division of Cooper Industries
Pepperl + Fuchs Inc.
Phoenix Contact Inc.
Fisher Controls Intl. Inc.
PC & E Inc.
Bently Nevada Corp.
Schlumberger Oilfield Services
Ametek Inc.
Waldemar S. Nelson & Company Inc.
Copyright 2003 ISA. All rights reserved.
This is a preview. Click here to purchase the full publication.
—5—
J. Costello
S. Czaniecki
T. Dubaniewicz
U. Dugar
A Engler
T. Feindel
W. Fiske
G. Garcha
D. Jagger
F. Kent
J. Kuczka
B. Larson
E. Magison
R. Masek
A. Mobley
A. Page
J. Propst
P. Schimmoeller
D. Wechsler
C. Wellman
ANSI/ISA-RP12.06.01-2003
Henkel Corporation
Intrinsic Safety Concepts Inc.
NIOSH
Mobil Chemical Company
EGS Electrical Group
R. Stahl Inc.
Intertek Testing Services
GE Power Systems
9 Darnton Gardens
Honeywell Inc.
Killark
Turck Inc.
Consultant
CSA International
3M Company
MSHA Approval & Certification Center
Equilon Enterprises
CSA International
Dow Chemical Company
DuPont Engineering
This document was approved for publication by the ISA Standards and Practices Board on 22 October
2002.
NAME
COMPANY
M. Zielinski, Chair
D. Bishop
D. Bouchard
M. Cohen
M. Coppler
B. Dumortier
W. Holland
E. Icayan
A. Iverson
R. Jones
V. Maggioli
T. McAvinew
A. McCauley, Jr.
G. McFarland
R. Reimer
J. Rennie
H. Sasajima
I. Verhappen
R. Webb
W. Weidman
J. Weiss
M. Widmeyer
C. Williams
G. Wood
Emerson Process Management
David N Bishop, Consultant
Paprican
Consultant
Ametek, Inc.
Schneider Electric
Southern Company
ACES Inc
Ivy Optiks
Dow Chemical Company
Feltronics Corporation
ForeRunner Corporation
Chagrin Valley Controls, Inc.
Westinghouse Process Control Inc.
Rockwell Automation
Factory Mutual Research Corporation
Yamatake Corporation
Syncrude Canada Ltd.
POWER Engineers
Parsons Energy & Chemicals Group
KEMA Consulting
Stanford Linear Accelerator Center
Eastman Kodak Company
Graeme Wood Consulting
Copyright 2003 ISA. All rights reserved.
This is a preview. Click here to purchase the full publication.
This page intentionally left blank.
This is a preview. Click here to purchase the full publication.
—7—
ANSI/ISA-RP12.06.01-2003
Table of Contents
Preface .......................................................................................................................................................... 3
1
Purpose ................................................................................................................................................ 9
2
Scope ................................................................................................................................................... 9
3
Definitions ............................................................................................................................................. 9
4
Article 504 and 505 of the NEC (ANSI/NFPA 70-2002) with explanation .......................................... 14
5
Guidelines for combinations of apparatus under the entity concept .................................................. 44
6
Maintenance and inspection............................................................................................................... 46
Annex A — Explanatory notes .................................................................................................................... 49
Annex B — Wiring in hazardous (classified) locations ............................................................................... 53
Annex C — Marking for the zone classification system .............................................................................. 55
Annex D — References .............................................................................................................................. 57
Copyright 2003 ISA. All rights reserved.
This is a preview. Click here to purchase the full publication.