ISO/TS 16952-1:2006

Technical product documentation - Reference designation system - Part 1: General application rules

ISO/TS 16952-1:2006 establishes comprehensive and practice-oriented principles and rules for the designation of technical objects within a system, as well as for the designation of connections, signals and documents in accordance with the corresponding basic standards. The principles of ISO/TS 16952-1:2006 apply to all technical fields for all industries and can be applied in all phases of the life cycle of a technical object. ISO/TS 16952-1:2006 serves as the basis for sector-specific parts of ISO/TS 16952 and thus forms the connecting element between them and the basic IEC 61346 series. The designation of types, individuals, cost-centres, projects, etc. is not covered by ISO/TS 16952-1:2006.

Documentation technique de produits — Système de désignation de référence — Partie 1: Règles générales d'application

General Information

• Status: Withdrawn
• Publication Date: 13-Jun-2006
• Withdrawal Date: 13-Jun-2006
• ICS: 01.110 - Technical product documentation
• Technical Committee: ISO/TC 10/SC 10 - Process plant documentation
• Drafting Committee: ISO/TC 10/SC 10/WG 10 - Reference designation system
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 11-Jul-2012
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO/TS 81346-3:2012 - Industrial systems, installations and equipment and industrial products - Structuring principles and reference designations - Part 3: Application rules for a reference designation system
• Effective Date: 09-Apr-2011

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 16952-1
First edition
2006-06-01
Technical product documentation —
Reference designation system —
Part 1:
General application rules
Documentation technique de produits — Système de désignation de
référence —
Partie 1: Règles générales d'application

Reference number
©
ISO 2006
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ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 2
4 Designation systematics. 4
4.1 General. 4
4.2 Designation process. 6
5 Tasks of designation . 7
5.1 General. 7
5.2 Conjoint designation . 8
5.3 Designation of technical objects. 9
5.4 Designation of other objects . 12
6 Construction of designation. 13
6.1 Syntax overview. 13
6.2 Conjoint designation . 14
6.3 Reference designation . 14
6.4 Specific designation. 16
Annex A (informative) Designation process within a project . 18
Annex B (informative) Application examples . 29
Annex C (informative) Other helpful terms and definitions for a “designation system”. 33
Bibliography . 46

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
It is intended, at the next revision of ISO/TS 16952-1 and of IEC 61346-1, to combine both documents into
one ISO/IEC standard with a 80000 number.
ISO/TS 16952-1 was prepared by Technical Committee ISO/TC 10, Technical product documentation,
Subcommittee SC 10, Process plant documentation and tpd-symbols.
ISO/TS 16952 consists of the following parts, under the general title Technical product documentation —
Reference designation system:
⎯ Part 1: General application rules
The following part is under preparation:
⎯ Part 10: Power plants
Further parts on sector-specific rules are under consideration.
iv © ISO 2006 – All rights reserved

Introduction
IEC 61346 is the basic standard for structuring principles and reference designation. IEC 61346-1 provides a
number of possibilities for the construction of reference designations. For most applications, however, only a
subset of the possibilities given in IEC 61346-1 need to be used. IEC 61346-1 does not restrict the use of the
reference designation system to a specific area. It is sometimes necessary to incorporate further basic
requirements, and it is recommended that these be specified and explained in supporting documentation.
To enhance an efficient implementation of those basic rules and to ensure a consistent interpretation of those
rules, an easily understandable system is necessary. Consequently, ISO/TS 16952:
⎯ offers broadly based, general solutions with rules for a practice-oriented and consistent application;
⎯ fulfils the requirements for ergonomics and occupational safety;
⎯ takes into account memorability, labelling, and processing in common office- and CAx-tools;
⎯ summarizes in a single document all technical designation tasks (reference designations according to
function, product and location aspect as well as designation of connections, signals, documents);
⎯ recommends decoupling of reference designation activities of plant designers and of equipment suppliers,
by use and allocation of different aspects;
⎯ introduces the “conjoint designation” for higher level objects without specific aspect;
⎯ supports the handling of computer programs and parts of such programs as technical products;
⎯ forms the basis for sector-specific solutions and specifications in further parts of ISO/TS 16952, in order
to achieve a consistent designation across different technical fields.
TECHNICAL SPECIFICATION ISO/TS 16952-1:2006(E)

Technical product documentation — Reference designation
system —
Part 1:
General application rules
1 Scope
This part of ISO/TS 16952 establishes comprehensive and practice-oriented principles and rules for the
designation of technical objects within a system, as well as for the designation of connections, signals and
documents in accordance with the corresponding basic standards.
The principles of this part of ISO/TS 16952 apply to all technical fields for all industries and can be applied in
all phases of the life cycle of a technical object.
This part of ISO/TS 16952 serves as the basis for sector-specific parts of ISO/TS 16952 and thus forms the
connecting element between them and the basic IEC 61346 series.
The designation of types, individuals, cost-centres, projects, etc. is not covered by this part of ISO/TS 16952.
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.
ISO 9355-1, Ergonomic requirements for the design of displays and control actuators — Part 1: Human
interactions with displays and control actuators
ISO 9355-2, Ergonomic requirements for the design of displays and control actuators — Part 2: Displays
ISO 12100-1, Safety of machinery — Basic concepts, general principles for design — Part 1: Basic
terminology, methodology
ISO 12100-2, Safety of machinery — Basic concepts, general principles for design — Part 2: Technical
principles
IEC 61175, Industrial systems, installations and equipment and industrial products — Designation of signals
IEC 61346-1:1996, Industrial systems, installations and equipment and industrial products — Structuring
principles and reference designations — Part 1: Basic rules
IEC 61346-2:2000, Industrial systems, installations and equipment and industrial products — Structuring
principles and reference designations — Part 2: Classification of objects and codes for classes
IEC 61355, Classification and designation of documents for plants, systems and equipment
IEC 61666, Industrial systems, installations and equipment and industrial products — Identification of
terminals within a system
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
aspect
specific way of selecting information on, or describing a system or an object of a system
[IEC 61346-1]
3.2
building
construction works that has the provision of shelter for its occupants or contents as one of its main purposes,
and which is usually partially or totally enclosed and designed to stand permanently in one place
[ISO 6707-1]
3.3
designation
generation of task-specific reference designations for technical objects in accordance with fixed rules
3.4
document
information on a data medium
NOTE 1 Normally a document is designated in accordance with the type of information and the form of presentation,
for example overview diagram, connection table, function chart.
NOTE 2 Information can appear in static manner on paper and microform, or dynamically on (video) display devices.
[IEC 61082-1]
3.5
document kind
type of document defined with respect to its specified content of information and form of presentation
[IEC 61355]
3.6
document kind class
group of document kinds having similar characteristics concerning the content of information independent of
the form of presentation
[IEC 61355]
3.7
documentation
collection of documents assigned to a specific object
NOTE This can include technical, commercial and/or other documents.
[IEC 61082-1]
2 © ISO 2006 – All rights reserved

3.8
function
purpose related to an object
[IEC 61346-1]
3.9
infrastructure
system of facilities, equipment and services required for the operation of an organization
[ISO 9000]
3.10
multi-level reference designation
reference designation derived from a structural path through an overall system
[IEC 61346-1]
3.11
object
entity treated in the process of design, engineering, realization, operation, maintenance and demolition
NOTE 1 The entity can refer to a physical or non-physical “thing”, or to a set of information associated with it.
NOTE 2 Depending on its purpose, an object can be viewed in different ways, called “aspects”.
[IEC 61346-1]
3.12
plant
complete set of technical equipment and facilities for solving a defined technical task
NOTE A plant includes apparatus, machines, instruments, devices, means of transportation, control equipment and
other operating equipment.
[IEC 60050-351]
3.13
process
sequence of chemical, physical or biological operations for the conversion, transport or storage of material or
energy
NOTE 1 Different processes or process steps can be carried out in the same process plant or plant section at different
times.
[ISO 10628]
NOTE 2 A process can also be regarded as an entirety of interacting events in a system through which material,
energy or information are transformed, transported or stored.
3.14
product
intended or accomplished result of labour, or of a natural or artificial process
NOTE 1 A product usually has a part number, order number, type designation, and/or a name.
NOTE 2 A technical system or plant can be considered as a product.
[IEC 61346-1]
3.15
reference designation
identifier of a specific object with respect to the system of which the object is a constituent, based on one or
more aspects of that system
[IEC 61346-1]
3.16
signal
identification of information and transferring of the information from an object to another
[IEC 61175]
3.17
single-level reference designation
reference designation assigned with respect to the object of which the specific object is a direct constituent
[IEC 61346-1]
3.18
structure
relations among the elements of a system
[IEC 60050-351]
3.19
system
set of interrelated objects
[IEC 61346-1]
3.20
terminal
point of access to an object intended for connection to an external network
NOTE 1 The connection can refer to:
⎯ a physical interface between conductors and/or contacts, or piping and/or duct systems to provide a signal, energy or
material flow path;
⎯ an association of functional nature established between logical elements, software modules, etc. for conveying
information.
NOTE 2 The external networks can be of different nature and accordingly they can be classified. IEC 81714-3 provides
such classifications.
[IEC 61666]
4 Designation systematics
4.1 General
4.1.1 Designation systematics is a well-ordered and methodical process of forming designations on the
basis of simple rules, ensuring compliance with the following requirements:
a) consistency in all phases (e.g. engineering, operation and decommissioning) and engineering disciplines
(e.g. process, civil, mechanical and electrical engineering) of a project;
4 © ISO 2006 – All rights reserved

b) fulfilment of ergonomic principles in accordance with ISO 12100-1, ISO 12100-2, ISO 9355-1 and
ISO 9355-2, with regard to occupational health and safety (hazard analysis, fault tracing, job orders,
equipment release procedures, etc.), e. g.
⎯ simple structure of designation,
⎯ easy-to-remember representation,
⎯ clear legibility and easy memorability,
⎯ error-free interpretation;
c) improvement of information management and information quality control, e.g. by establishing:
⎯ identifiers for data and document management systems,
⎯ identifiers for configuration and quality management systems,
⎯ clear cross-references between physical application and documentation.
The designation shall clearly and unambiguously identify all objects and associated information according to
their function, implementation and location.
The designation shall describe the real structure of an object and its relations to other objects.
The designation of the parts of a system shall be generic to such an extent that the system can be
incorporated in any other system, without the need for changing the reference designations in any of the
systems involved.
4.1.2 IEC 61346-1 provides a number of possibilities for the construction of reference designation. For most
applications, however, only a subset of the possibilities given in IEC 61346-1 need to be used. For a
consistent application in practice, this part of ISO/TS 16952 establishes clear and easily understandable rules
and guidelines as well as well-defined specifications for the following:
⎯ tasks of designation (see Clause 5),
⎯ general and sector neutral construction of designation (see Clause 6).
4.1.3 This part of ISO/TS 16952 stipulates only basic rules. Detailed and specific requirements are given in
the sector-specific parts of ISO/TS 16952, in order to cover the specific needs of different application fields.
These specific requirements comprise:
⎯ a relevant subset of designation possibilities,
⎯ letter codes for infrastructure objects,
⎯ a reference designation that identifies the object unambiguously (main aspect),
⎯ transitions between different aspects,
⎯ a sector-specific designation structure,
⎯ the allocation of structural levels to letter code tables,
⎯ additional aspects.
4.1.4 Furthermore, the following specifications need to be established and documented for each project:
⎯ conjoint allocation,
⎯ notation, e.g. in documents, on labels, on displays.
4.1.5 The chosen structure, with corresponding reference designations, shall be documented not only in
relevant object describing documents, but also in a separate document describing the structure.
For a specific project, the general rules shall be listed at the start of the designation process and documented
complete with specific requirements in separate instructions.
4.1.6 An example of a designation process within a project is given in Annex A. Application examples are
given in Annex B. Other terms and definitions that are used in the context of a “designation system” and will
be helpful for the elaboration of sector-specific parts of ISO/TS 16952 are given in Annex C.
4.2 Designation process
The designation process comprises the following sub-processes.
Starting from process flow diagrams, overview diagrams, site plans, etc. used to describe the structure of the
overall project in accordance with IEC 61346-1, the overall object shall be broken down according to different
viewpoints. For instance, a location with industrial facilities can be divided into specific areas (e.g.
manufacture, power plant). These objects shall be defined as top-level nodes of the overall structure and shall
serve as starting point for subdivisions into lower-level aspect-oriented structures (see 5.3.1).
At an early stage in the planning, the task-oriented representations of the object of interest shall be translated
into a hierarchical tree-like structure under a functional aspect. In subsequent phases, the products that fulfil
the tasks of the partial objects viewed under functional aspects shall be defined and structured. To designate
the location of the products, the overall object shall be structured under the location aspect. Structuring shall
be performed in compliance with the principle of constituency, i.e. an object is a constituent of a single higher
object, but can comprise several sub-objects (hierarchical structural model). The subdividing process is
completed with the smallest object of interest for the defined purpose.
Partial objects shall be defined and classified during the structuring process. To classify partial objects, it is
possible to use IEC 61346-2:2000, Table 1, for non aspect-specific purposes and/or sector- or project-specific
letter code tables structured in accordance with IEC 61346-2:2000, Table 2. In cases where both methods are
used, the allocations of the structural level to the corresponding letter code level shall be defined. The parts of
an object shall be classified in accordance with their location in the structure (structural level), as specified by
the agreed tables.
The prefix for the aspect, the letter code of the object class and an additional number form the single-level
reference designation. The number is used to distinguish between objects belonging to the same class and to
the same overall object. The multi-level reference designation is created by concatenating the single-level
reference designations represented in the path beginning with the top-most one.
To establish a unique designation, it is necessary to create task-specific designation combinations (in relation
to technical objects, signals, connections, documents), as described in Clause 6.
The designation shall be used for labelling technical objects in the plant, for designating documents and for
identifying the representation of objects in documents.
Reference designations with different aspects can be used in databases to network object information in
different records (“pragmatic relations”). This yields a large number of task-related evaluation options, e.g.
information about the location of products performing a function and which are reported as defective.
Figure 1 shows the schematic representation of the designation process.
6 © ISO 2006 – All rights reserved

Figure 1 — Schematic representation of the designation process
5 Tasks of designation
5.1 General
A reference designation shall:
⎯ identify an object,
⎯ provide information regarding the class to which the object belongs, and
⎯ provide information on where the object is located within a structure.
5.2 Conjoint designation
It is recognized that on a site different plants may exist. In order to address these plants with respect to the
site, it may be necessary to apply a conjoint designation. A conjoint designation is a reference designation of a
plant/system with respect to the site, which is not related to one of the defined aspects.
The use of the conjoint designation is optional. The application, structure and number of data characters shall
be defined project-specifically.
If this designation is used as part of the identifier (see 6.1), the systems, objects and products which fulfil the
same task in different plants can have the same reference designation. Unambiguous designations are
obtained by means of the different conjoint designations. There is a significant ergonomic advantage in
adopting this approach. Even if the equipment is moved from plant to plant, the necessary changes of its
designation are limited. The same principle applies to designations of locations.

Figure 2 — Conjoint designation, designation principle
8 © ISO 2006 – All rights reserved

5.3 Designation of technical objects
5.3.1 Reference designation
5.3.1.1 Aspects
IEC 61346-1:1996 specifies that “the reference designation identifies objects for the purpose of correlating
information about an object among different kinds of documents and the products implementing the system”.
A system, and each constituent object, can be viewed in many ways, called “aspects” (see Figure 3).
Questions:
⎯ What does the object do? (function aspect)
⎯ How is the object constructed? (product aspect)
⎯ Where is the object located? (location aspect)

Explanations:
⎯ Materials are to be conveyed in a transport process. This task requires electrical energy, which shall be switched by a
control. The equipment shall be protected from the effects of short circuit and overload (function aspect).
⎯ A breaker with contacts is part of a cabinet (product aspect).
⎯ A building with floors and a number of rooms (location aspect).
Figure 3 — Aspects
5.3.1.2 Structures
With respect to the three types of aspects considered in 5.3.1.1, and following the rule of constituent objects,
three independent structures can be generated (see Figure 4).

Explanations:
The relations of objects (represented by nodes) within one structure tree are partitive relations, e.g.
⎯ the cabinet consists of the breaker, etc.; the breaker consists of contacts, etc.;
⎯ the contact is a constituent of the breaker, the breaker is a constituent of the cabinet.
The relations of objects (represented by nodes) between different structure trees are associative (pragmatic) relations
(indicated by dotted lines), which opens numerous options for the extraction of comprehensive information regarding the
plant, e.g.
⎯ the basic tasks of switching and protecting are implemented with a breaker: this device is part of a cabinet, which is
installed in a certain room on a floor of a building;
⎯ a room contains cabinets with breakers, one of which performs the functions of switching and protecting within the
transporting process.
Figure 4 — Structures and relations
5.3.2 Designation of function-oriented structure
The function aspect shall be based on the purpose of the system, without necessarily taking into account the
products used to fulfil this purpose or their location.
An additional aspect of the function type enables distinction to be drawn between, e.g.:
⎯ functional units with dynamic effects,
⎯ the control function view,
⎯ the energy supply function view.
10 © ISO 2006 – All rights reserved

A precise definition shall be documented in the sector-specific parts of ISO/TS 16952.
The designation based on the function aspect is preferably performed in the early planning phase of a project
without taking implementation into account. Normally, this type of designation is first used by the planner of
the overall process (top-down approach).
5.3.3 Designation of product-oriented structure
The product aspect shall be based on the way in which a system is implemented, constructed or delivered,
without necessarily taking into account functions and/or locations.
The designation based on the product aspect is, for example, used for assemblies, indicating the way an
assembly is built up from its parts without necessarily taking into account the functions and/or locations.
An additional aspect of the product type enables a distinction to be made for purposes to be defined in
supporting documentation.
5.3.4 Designation of location-oriented structure
The location aspect shall be based on the topographical layout of a system, without necessarily taking into
account products and/or functions.
An additional aspect of the location type enables a distinction to be drawn between:
⎯ the designation of locations within design modules (installation aspect) as well as designation of locations
on machinery components (mounting aspect), and
⎯ the designation of the plant topology (erection aspect).
The designation based on the location aspect is preferably used for the designation of objects which fulfil the
task of providing locations for other objects. The plant designer normally uses this type of designation for
assigning the equipment parts to their locations (i.e. installation, mounting, set-up).
5.3.5 Designation of objects using different aspects
It is often expedient to use different aspects for the same object. Different aspects of successive objects may
be used by making a transition from one aspect to another.
The most frequent application of this method is the transition from the function to the product aspect when a
function is completely implemented by a product, and when there is no sub-product that by itself completely
implements the function.
Figure 5 shows the transition from the function aspect to the product aspect, and presents the difference
between transition and allocation.
Explanation:
The product-oriented designation -F1 of the sub-product “fuse” is added to the function-oriented designation =Q1 of the
function “supply” (in the sense of “is a constituent of”) and, in this combination, forms a clear and unambiguous
designation.
Figure 5 — Transition from function aspect to product aspect
Application of this method enables product-specific assignment of designations for independent products by
the manufacturer, which can then be easily attached to existing function-oriented structures and designations.
Further guidelines on the application of transitions are given in the sector-specific parts of ISO/TS 16952.
5.4 Designation of other objects
5.4.1 Designation of signals
If a designation is required, signals shall be designated unambiguously (see 6.4.3).
A signal represents information that is transferred between objects independent of the medium used for the
transfer.
The signal designation is an important means of co-ordinating the data flow and serves as a pathfinder in
technical control documentation.
5.4.2 Designation of terminals
If a designation is required, terminals shall be designated unambiguously (see 6.4.4).
Terminals are points of access to an object for connection to different kinds of external networks. In addition to
electrical networks, terminals of products may also provide facilities for a connection to piping systems, for the
flow of material or energy, signals, etc.
Electrical, mechanical and functional terminals of different objects shall be clearly designated.
12 © ISO 2006 – All rights reserved

5.4.3 Designation of documents
If a designation is required, documents shall be designated unambiguously (e.g. by drawing number).
Documents provide information necessary for different activities and purposes during the life cycle of a plant,
system or equipment.
The document designation helps to provide clear addresses on and in documents, and is also a unique
address in document management systems.
If, in addition to an unambiguous designation, a designation with respect to the object represented in the
document is required, the rules given in 6.4.5 shall apply.
6 Construction of designation
6.1 Syntax overview
The variety of industrial systems, installations, equipment and industrial products, as well as the different
aspects they are viewed from, necessitates different designations that reflect this variety accordingly. The
solution is an identifier that consists of three main parts (see Figure 6), which are constructed differently
according to their purpose and task.
The three parts of the identifier are:
⎯ conjoint designation (see 6.2);
⎯ reference designation (see 6.3);
⎯ specific designation (see 6.4).

Figure 6 — Parts of the identifier
NOTE For documents, “reference designation” is called “object designation” (see 6.4.5).
Because of the designation needs in different technical fields, the combinations of the identifier parts can be
numerous. Table 1 shows some frequently-occurring examples. In most cases, the reference designation is
an integral part of the identifier, while the conjoint designation is an optional element and the specific
designation is used where appropriate.
Table 1 — Examples of combinations of the parts of the identifier
Conjoint designation
Conjoint designation Reference designation
Conjoint designation Reference designation Specific designation
Conjoint designation Specific designation
Reference designation
Reference designation Specific designation
6.2 Conjoint designation
The conjoint designation shall consist of the prefix “#” followed by a sequence of characters (letters and/or
numbers) which should not exceed 12. In the case of letters, capital Latin letters shall be used. The letters “I”
and “O” should not be used if there is the possibility of confusion with the digits “1” and “0”. In the case of
numbers, the Arabic digits “1” to “9” and “0” (zero) shall be used.
If the conjoint designation is used, it shall form the first part of the identifier.
The structure of the conjoint designation is given in Figure 7.

Figure 7 — Structure of the conjoint designation
6.3 Reference designation
6.3.1 Single-level reference designation
IEC 61346-1 allows three variants for the construction of a single-level reference designation. A single-level
reference designation assigned to an object shall consist of a prefix followed either by:
⎯ a letter code;
⎯ a letter code followed by a number;
⎯ a number.
If requirements for ergonomics and occupational safety (e.g. legibility, memorability, error-free interpretation)
are to be fulfilled, the single-level reference designation shall be constructed as shown in Figure 8.

Figure 8 — Structure of a single-level reference designation
To satisfy the needs of legibility and memorability, there should not be more than three letters or numbers.
14 © ISO 2006 – All rights reserved

6.3.2 Multi-level reference designation
A multi-level reference designation is a coded representation of the path from the top of a structure down to
the object of interest. It shall be constructed by concatenating the single-level reference designation for each
object represented in the path, beginning with the top-most one.
If the prefix for a single-level reference designation is the same as for the preceding single-level reference
designation, the prefix may be omitted within the multi-level reference designation for the presentation,
provided that the preceding designation ends with a number and the following designation starts with a letter
code.
6.3.3 Prefixes
Because of its function to indicate the aspect, the prefix is an essential part of the reference designation and
shall always be shown. In accordance with IEC 61346-1, if additional views of an aspect are required, the
designation shall be formed by doubling, tripling, etc. the prefix (see Table 2).
Table 2 — Prefixes for reference designation
Prefix Aspect
= Function
== Function (another aspect)
– Product
- - Product (another aspect)
+ Location based on the location within the packaging system
a
++ Location based on the topography of the plant

a
See example in IEC 61346-1:1996, Figure 23.
6.3.4 Letter codes
The letters of the reference designation indicate the object or the class of objects according to purpose or
task.
IEC 61346–2 offers two tables with letter codes and rules for subclasses for coequal application.
⎯ Table 1 defines classes of objects and associated letter codes generally for all applications.
⎯ Table 2 provides a frame for setting up classification schemes and gives examples for classes of
infrastructure objects.
The use of IEC 61346-2:2000, Table 1, is mandatory. If supplementary subclasses are necessary, they shall
be specified in sector-specific or project-related documents.
If both tables are used, an indication shall be made of the table from which a certain reference level is
implemented.
Letter codes shall be formed using capital Latin letters, excluding “I” and “O” because of possible confusion
with the digits “1” (one) and “0” (zero). Mnemotechnical and local characters shall be omitted to enhance
international usability.
6.3.5 Numbers
Numbers serve to differentiate between objects with the same preceding designation elements.
The Arabic digits “1” to “9” and “0” (zero) shall be used.
6.4 Specific designation
6.4.1 General
The specific designation shall designate:
⎯ signal names, in accordance with IEC 61175;
⎯ electrical, mechanical and functional terminals, in accordance with IEC 61666;
⎯ document kinds, in accordance with IEC 61355.
NOTE In ISO terminology, “document kinds” are referred to as “document types”.
The specific designation may consist of:
⎯ the prefix (see 6.4.2 and Table 2, Footnote),
⎯ letter codes,
⎯ numbers,
and shall be constructed as shown in Figure 9.

Figure 9 — Structure of the specific designation
Within a system/plant, this part of the identifier is only unambiguous in connection with the reference
designation/object designation or/and conjoint designation.
6.4.2 Prefixes
For prefixes for specific designations, see Table 3.
Table 3 — Prefixes for specific designation
Prefix Task
; Signal designation
a
Terminal designation
:
& Document designation
a
In IEC 61666, used as a separator between reference designation and terminal designation and not as

part of the terminal designation.

16 © ISO 2006 – All rights reserved

6.4.3 Signal designation
Signals shall be identified with respect to the object, by means of an unambiguous and valid signal name and
a signal designation in accordance with IEC 61175 (see Figure 10).

Figure 10 — Signal designation
6.4.4 Terminal designation
Terminals shall be identified with respect to the object to which they belong and in accordance with IEC 61666
(see Figure 11).
Figure 11 — Terminal designation
6.4.5 Document designation
Documents may be identified with respect to the object to which the document is assigned and with a
classification code independent of supplier-specific numbering systems in accordance with IEC 61355 (see
Figure 12).
Figure 12 — Document designation
The reference designation is generally used as the object designation.

Annex A
(informative)
Designation process within a project
A.1 General
This Annex shows, by means of a sample project, the designation process within a project:
⎯ implemented project-related stipulations (see A.2);
⎯ application examples for different project disciplines, e.g. civil, process, electro- and control engineering
(see A.3);
⎯ an example of a database analysis and its representation (see A.3.6).
A.2 Project-related stipulations
At the beginning of a project, the designation-relevant stipulations indicated in Table A.1 should be respected.
Table A.1 — General stipulations
Subject Stipulations (examples)
Designation range Conjoint designation (#), function (=), product (-), point of installation (+),
document (&)
Main aspect Function (=)
Allowed transitions From function aspect to product aspect
Additional aspects Location (++)
Counting directions From south to north, from west to east

If the conjoint designation is to be used in the project, the overall plant structure should be considered and the
structure of the conjoint designation should be fixed accordingly. The structure of the conjoint designation (see
examples in Table A.2) and the project-related application rules should be written down in a project-specific
designation management document.
Table A.2 — Examples of conjoint designation
Conjoint designation Description
#WORK1 AD1 Administration 1
#WORK1 CP1 Chemical plant 1
#WORK1 CP2 Chemical plant 2
#WORK1 CP3 Chemical plant 3
#WORK1 PP1 Power plant 1
18 © ISO 2006 – All rights reserved

The configuration of the reference designation structural levels should be decided in accordance with this
structure. For each level, the classification should be allocated in accordance with IEC 61346-2:2000, Table 1
and Table 2 or the sector-specific classification tables. Table A.3 gives an example of such a structuring and
classification allocation:
Table A.3 — Structural levels, allocation of classifications and alphanumerical structure
Level L1 L2 L3 L4
Data type AN AANN AANN AANN
Corresponding table
Table A.4 Table A.5 Table A.5 Table A.5

The classes of infrastructure objects (level L1 in Table A.3) are based on the rules of IEC 61346-2:2000,
Clause 6 and Table 2. If sub-classes are necessary, IEC 61346-2:2000, Clause 7, should be considered.
Table A.4 gives examples of infrastructure objects of a chemical plant.
Table A.4 — Infrastructure objects
Letter code Description
D1 Crushing plant
E1 Dissolution plant
E2 Reaction plant
E3 Concentration plant
G1 Recovery plant
F1 Distillation
H1 Waste scrubbing plant
S1 Electrical power system
For levels L2, L3 and L4 in Table A.3, the object classes according to IEC 61346-2:2000, Table 1, should be
used. The sub-classes (second letter) are chosen from IEC/PAS 62400. Table A.5 gives examples of letter
codes for the classification of aspect-oriented structures.
Table A.5 — Classes of aspect-oriented object structures
Function aspect Product aspect
Letter code
(function unit) (design unit)
BT Temperature measurement Temperature sensor
CM Storage of materials Tank, silo
EP Generation of heat energy by energy transfer Condenser, heat exchanger
FL Protection from hazardous pressure conditions Safety valve
GP Conveyance of liquid substances Pump
HP Separation by thermal processes Distillation column
HQ Separation by filtering Fluid filter
KF Processing of electrical and electronic signals Controller
MA Driving by electric motor Electric motor
PF Presentation of information (permanent) Recorder, printer
QA Switching of electrical energy circuits Circuit breaker
QC Grounding of electrical energy circuits Grounder
QM Limiting of flow in closed enclosu
...