IEC 81346-2:2009

Industrial systems, installations and equipment and industrial products - Structuring principles and reference designations - Part 2: Classification of objects and codes for classes

IEC 81346-2:2009, published jointly by IEC and ISO defines classes and subclasses of objects based on a purpose- or task-related view of the objects, together with their associated letter codes to be used in reference designations. The classification is applicable for objects in all technical areas, e.g. electrical, mechanical and civil engineering as well as all branches of industry, e.g. energy, chemical industry, building technology, shipbuilding and marine technology, and can be used by all technical disciplines in any design process. It has the status of a horizontal standard in accordance with IEC Guide 108.

Systèmes industriels, installations et appareils, et produits industriels - Principes de structuration et désignations de référence - Partie 2: Classification des objets et codes pour les classes

La CEI 81346-2:2009 publiée conjointement par le CEI et l'ISO définit les classes et les sous-classes d'objets basées sur une vision des objets liée à l'objectif ou à la tâche concerné(e), ainsi que leurs lettres codes associées, à utiliser dans les désignations de référence. La classification est applicable aux objets appartenant à tous les domaines techniques, par exemple génie civil, électrique, mécanique et aussi bien que toutes les branches d'industrie, par exemple énergie, industrie chimique, technologie de la construction, construction navale et technologie marine et dans tout processus de conception. Elle a le statut de norme horizontale conformément au Guide IEC 108.

General Information

• Status: Published
• Publication Date: 29-Jul-2009
• ICS: 01.110 - Technical product documentation
• ICS: 29.020 - Electrical engineering in general
• Technical Committee: TC 3 - Documentation, graphical symbols and representations of technical information
• Drafting Committee: MT 18 - TC 3/MT 18
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 18-Jun-2019

Relations

• Revised: IEC 81346-2:2019 - Industrial systems, installations and equipment and industrial products - Structuring principles and reference designations - Part 2: Classification of objects and codes for classes
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 81346-2



Edition 1.0 2009-07



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE
Industrial systems, installations and equipment and industrial products –
Structuring principles and reference designations –
Part 2: Classification of objects and codes for classes

Systèmes industriels, installations et appareils, et produits industriels –
Principes de structuration et désignations de référence –
Partie 2: Classification des objets et codes pour les classes


IEC 81346-2:2009

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IEC 81346-2



Edition 1.0 2009-07



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE
Industrial systems, installations and equipment and industrial products –
Structuring principles and reference designations –
Part 2: Classification of objects and codes for classes

Systèmes industriels, installations et appareils, et produits industriels –
Principes de structuration et désignations de référence –
Partie 2: Classification des objets et codes pour les classes


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 01.110; 29.020 ISBN 978-2-88910-786-5

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CONTENTS

FOREWORD.4


INTRODUCTION.6

0.1 General.6

0.2 Basic requirements for this standard .6

1 Scope.8


2 Normative references .8

3 Terms and definitions .8

4 Classification principles .8
4.1 General .8
4.2 Assigning objects to classes.9
5 Classes of objects .11
5.1 Classes of objects according to intended purpose or task.11
5.2 Subclasses of objects according to intended purpose or task .17
5.3 Classes of objects according to infrastructure .36
Annex A (informative) Object-classes related to a generic process .39
Annex B (informative) Object-classes related to objects in a generic infrastructure .41

Figure 1 – Constituent objects .7
Figure 2 – The basic concept.8
Figure 3 – Classification of objects in a measuring circuit .10
Figure A.1 – Object-classes related to a process .39
Figure B.1 – Object-classes related to objects in a generic infrastructure.42

Table 1 – Classes of objects according to their intended purpose or task (Codes A to D).12
Table 1 (continued, codes E to J).13
Table 1 (continued, codes K to P) .14
Table 1 (continued, codes Q to U) .15
Table 1 (continued, codes V to Z) .16
Table 2 – Definitions and letter codes of subclasses related to main classes (Class A).18
Table 2 (continued, class B) .19

Table 2 (continued, class C) .20
Table 2 (continued, class E) .21
Table 2 (continued, class F).22
Table 2 (continued, class G) .23
Table 2 (continued, class H) .24
Table 2 (continued, class K) .25
Table 2 (continued, class M) .26
Table 2 (continued, class P) .27
Table 2 (continued, class Q) .28
Table 2 (continued, class R) .29
Table 2 (continued, class S) .30
Table 2 (continued, class T).31

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81346-2 © IEC:2009 – 3 –


Table 2 (continued, class U) .32

Table 2 (continued, class V) .33


Table 2 (continued, class W).34

Table 2 (continued, class X) .35

Table 3 – Classes of infrastructure objects .37


Table 4 – Examples of branch-related classes B to U of Table 3 .38

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INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________



INDUSTRIAL SYSTEMS, INSTALLATIONS

AND EQUIPMENT AND INDUSTRIAL PRODUCTS –

STRUCTURING PRINCIPLES AND REFERENCE DESIGNATIONS –



Part 2: Classification of objects and codes for classes





FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
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consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 81346-2 has been prepared by IEC technical committee 3:
Information structures, documentation and graphical symbols and ISO technical committee
10: Technical product documentation.
It is published as a double logo standard.
This edition cancels and replaces the first edition of IEC 61346-2, published in 2000 and the
first edition of IEC/PAS 62400, published in 2005.
This edition includes the following technical changes with respect to IEC 61346-2 Ed.1:
• all rules concerning the application of letter codes have been removed as these should be
included in another publication dealing with the application of letter codes within reference
designations;
and, with respect to IEC/PAS 62400 Ed.1:

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81346-2 © IEC:2009 – 5 –


• the definitions of the sub-classes have been reviewed and made consistent;


• the basis for the sub-classification is indicated;

• some new subclasses for class B and class P have been added;

• the table of terms sorted according to the two-letter code has been removed;


The text of this standard is based on the following documents:


FDIS Report on voting

3/945/FDIS 3/957RVD


Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table. In ISO, the standard has been approved by 12 members
out of 13 having cast a vote.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 81346 series, formerly IEC 61346 series, published under the general
title Industrial systems, installations and equipment and industrial products – Structuring
principles and reference designations, can be found on the IEC website.
Future standards in this series will carry the new general number 81346. Numbers of existing
standards in this series will be updated at the time of the next edition.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under “http://webstore.iec.ch” in the
data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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INTRODUCTION



0.1 General


The aim of this part of IEC 81346 is to establish classification schemes for objects with

associated letter codes which can be applied throughout all technical areas, e.g. electrical,

mechanical and civil engineering as well as all branches of industry, e.g. energy, chemical

industry, building technology, shipbuilding and marine technology. The letter codes are

intended for use with the rules for the construction of reference designations in accordance

with IEC 81346-1.

Annex A illustrates how objects may be classified according to their intended purpose or task
related to a generic process.
Annex B illustrates how objects may be classified according to their position in an
infrastructure.
0.2 Basic requirements for this standard
The basic requirements were developed during the preparation of IEC 61346-2 Ed. 1, and
accepted by vote by the national committees.
NOTE These basic requirements concern the development of the letter code classification system in this standard
and not its application. They are therefore not normative vis-à-vis the application of this standard.
(1) Letter codes shall be based on a classification scheme.
(2) A classification scheme is the set of definitions for the types of objects (for example, a
classification scheme for function types containing the definition of the different function
types of objects).
(3) A classification scheme shall allow for hierarchical classification of types of objects, i.e.
subclasses and superclasses.
(4) A letter code for a type of object shall be independent of the actual position of the
instances of that type of object in a system.
(5) Distinct classes shall be defined on each level of the classification scheme.
(6) The definitions of the classes of a particular level within a classification scheme shall
have a common basis (for example, a classification scheme that, on one level, classifies
objects according to colour shall not contain classes that classify objects by shape). The
basis, however, may vary from one level to another.
(7) A letter code should indicate the type of object and not an aspect of this object.

(8) A classification scheme shall allow for expansion in order to take into account future
development and needs.
(9) A classification scheme shall be usable within all technical areas without favouring a
specific area.
(10) It shall be possible to use the letter codes consistently throughout all technical areas.
The same type of object should preferably have only one letter code independent of the
technical area where it is being used.
(11) It should be possible to indicate in a letter code from which technical area the object
originates, if this is wanted.
(12) A classification scheme should reflect the practical application of letter codes.
(13) Letter codes should not be mnemonic, as this cannot be implemented consistently
throughout a classification scheme and for different languages.
(14) Letter codes shall be formed using capital letters from the Latin alphabet, excluding I
and O due to possible confusion with the digits 1 (one) and 0 (zero).

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81346-2 © IEC:2009 – 7 –


(15) Different classification schemes shall be allowed and be applicable for the same type of

object.

(16) Objects may be classified for example according to function types, shapes, colours, or

material. This means that the same type of object may be assigned different letter

codes according to the different classification schemes.

(17) Objects that are directly constituents of another object using the same aspect shall be

assigned letter codes according to the same classification scheme as shown in Figure

1. See also Figure A.1.





IEC  1272/09


Objects 2, 3, and 4, which are direct constituents of object 1, shall be assigned letter codes from the same
classification scheme.
Objects 5 and 6, which are direct constituents of object 2, shall be assigned letter codes from the same
classification scheme.
Objects 7 and 8, which are direct constituents of object 4, shall be assigned letter codes from the same
classification scheme.
Objects 9, 10, 11, and 12, which are direct constituents of object 6, shall be assigned letter codes from the same
classification scheme.
Objecst 13, 14, 15, and 16, which are direct constituents of object 8, shall be assigned letter codes from the same
classification scheme.
Figure 1 – Constituent objects

(18) If products from different manufacturers are combined into a new product, the
constituents of this product may be assigned codes according to different classification
schemes.

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INDUSTRIAL SYSTEMS, INSTALLATIONS

AND EQUIPMENT AND INDUSTRIAL PRODUCTS –

STRUCTURING PRINCIPLES AND REFERENCE DESIGNATIONS –



Part 2: Classification of objects and codes for classes






1 Scope


This part of International Standard 81346, published jointly by IEC and ISO defines classes
and subclasses of objects based on a purpose- or task-related view of the objects, together
with their associated letter codes to be used in reference designations.
The classification is applicable for objects in all technical areas, e.g. electrical, mechanical
and civil engineering as well as all branches of industry, e.g. energy, chemical industry,
building technology, shipbuilding and marine technology, and can be used by all technical
disciplines in any design process.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 81346-1, Industrial systems, installations and equipment and industrial products –
Structuring principles and reference designations – Part 1: Basic rules
ISO 14617-6:2002 Graphical symbols for diagrams – Part 6: Measurement and control
functions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 81346-1 apply.
4 Classification principles
4.1 General

The principle of classification of objects is based on viewing each object as a means for
performing an activity often with input and output (see Figure 2). In this respect, the internal
structure of an object is not important.

IEC  1273/09
Figure 2 – The basic concept

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81346-2 © IEC:2009 – 9 –


 Annex A shows the generic process model used for the establishment of the classification
scheme based on intended purpose or task as shown in Table 1.


An alternative classification according to purpose or task in the special case of an object
regarded as part of an infrastructure is presented in Table 3.


Each class defined in Table 1 is in this standard associated with a set of predefined
subclasses allowing a more detailed characterization of a component, if required. The

definitions of subclasses of objects are presented in Table 2 together with their associated

letter codes of class and subclass.


NOTE 1 Subclasses do not define a new level in a structure, i.e. they do not describe a subdivision of the object.
Class and subclass refer to the same object.
NOTE 2 The use of subclasses for the coding of technical attributes should be avoided, as this is a separate kind
of information presented in the documentation, for example in a technical specification or in a parts list.
4.2 Assigning objects to classes
For the assignment of objects (i.e. components belonging to the system under consideration)
to classes, the following rules apply:
Rule 1 For the classification of objects according to their intended purpose or task, main
classes and letter codes in accordance with Table 1 or Table 3 shall be applied.
Rule 2 For assigning an object to a class according to Table 1 or Table 3, the object shall
be viewed with respect to its intended purpose or task, as a component in the
system under consideration, without considering the means for implementation
(e.g. the kind of product).
EXAMPLE The desired purpose of an object is “heating”. A possible component required to fulfil this
is a “heater”. According to Table 1, this object is clearly related to class E. It is not of importance, or
simply not known at an early stage of a design process, how the required purpose is realized. This
needed component may be satisfied by using a gas or oil burner or an electric heater (which all may
be products delivered by others). In the case of an electric heater, the heat may be produced by a
product called electric resistor. This product may, in other cases, be classified by its purpose
“restricting a flow” according to class R if that describes it use as a component in those contexts.
It is the component that is classified – not the product used for implementation!
Rule 3 For objects with more than one intended purpose or task, the object shall be
classified according to the intended purpose or task considered to be the main
one.
Table 1 shall only be applied for objects
Rule 4 The class with letter code A according to
with no explicit main purpose or task.

EXAMPLE A flow rate recorder stores measured values for later use but, at the same time, delivers
an output in visible form. If storing is regarded as the main purpose, the object is related to class C
of Table 1. If the indication of measured values is regarded as the main purpose, the object is
related to class P. If the two purposes are considered equally valid, the object is related to class A.
Figure 3 illustrates the principle of assigning classes to objects in the case of a measuring
circuit. The left-hand side illustrates how the requirements are turned into objects with input
and output. On the right-hand side, the used components are shown.

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Required process activity








Required system object




Different possible realizations
a) Direct measuring and indication


b) Measuring and indication circuit consisting of discrete components


c) One device integrating discrete components
Indicating device
Class P
Transducer
Instrument
Sensor
class T
class P
class B
Indicated,
measured
property

Classification of internal
components is of interest only
Process flow if they are accessible.


d) One device integrating discrete components and for combined purposes; for measuring (primary purpose),
and for indicating (secondary purpose)


IEC  1274/09
NOTE The classes are taken from Table 1.
Figure 3 – Classification of objects in a measuring circuit

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81346-2 © IEC:2009 – 11 –


5 Classes of objects


5.1 Classes of objects according to intended purpose or task


Table 1 constitutes the main classification method applicable for any object from any field of

technology.


The most important element in the table is the description of the intended purpose or task of

an object to which it is to be referred when searching for an appropriate class for an object.

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Table 1 – Classes of objects according to their intended purpose or task
(Codes A to D)


Code Intended purpose or Examples of terms Examples of typical Examples of typical

task of object describing the mechanical/fluid electrical components

intended purpose or components
task of objects


A Two or more purposes or
tasks


NOTE This class is only
for objects for which no

main intended purpose

or task can be identified.
B Converting an input Detecting Orifice plate (for Buchholz relay
variable (physical Measuring (picking-up of measuring) Current transformer
property, condition or values) Sensor Flame detector
event) into a signal for Monitoring Measuring relay
further processing Sensing Measuring shunt
Weighing (picking-up of  (resistance)
values) Microphone
Movement detector
Overload relay
Photocell
Position switch
Proximity sensor
Proximity switch
Smoke s
...