Classification of environmental conditions - Part 3-4: Classification of groups of environmental parameters and their severities - Stationary use at non-weatherprotected locations

IEC 60721-3-4:2019 classifies groups of environmental parameters and their severities to which products are subjected when installed for stationary use at non-weatherprotected locations. Weatherprotected locations where products can be mounted for stationary use permanently or temporarily are addressed in IEC 60721-3-3.
This third edition cancels and replaces the second edition published in 1995 and Amendment 1:1996. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Clause 1: reworded.
b) Clause 2: normative references have been updated.
c) Clause 3: definitions have been updated.
d) Clause 4: reworded and simplified.
e) Clause 5: revised and updated. Several classes have been replaced by completely new classes based on the use of new information obtained from referenced technical reports.
f) Defined values of chemically active substances are now by reference to ISO 9223.
g) Tables 1 through 5: updated.

Classification des conditions d'environnement - Partie 3-4: Classification des groupements des agents d'environnement et de leurs sévérités - Utilisation à poste fixe, non protégé contre les intempéries

L’IEC 60721-3-4:2019 classifie les groupements d’agents d’environnement et leurs sévérités, auxquels sont soumis des produits montés pour une utilisation à poste fixe dans des emplacements non protégés contre les intempéries. Les emplacements protégés contre les intempéries où peuvent être montés les produits pour une utilisation fixe de manière permanente ou temporaire sont traités dans l’IEC 60721-3-3.
Cette troisième édition annule et remplace la deuxième édition parue en 1995, ainsi que son amendement 1:1996. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) Article 1: reformulation.
b) Article 2: mise à jour des références normatives.
c) Article 3: mise à jour des définitions.
d) Article 4: reformulation et simplification.
e) Article 5: révision et mise à jour. Plusieurs catégories ont été remplacées par des catégories totalement nouvelles fondées sur l’utilisation de nouvelles informations obtenues dans les rapports techniques cités en référence;
f) Les valeurs définies des substances chimiquement actives font désormais référence à l’ISO 9223.
g) Tableaux 1 à 5: mise à jour.

General Information

Status
Published
Publication Date
21-May-2019
Current Stage
PPUB - Publication issued
Completion Date
22-May-2019
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IEC 60721-3-4
Edition 3.0 2019-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 3-4: Classification of groups of environmental parameters and their
severities – Stationary use at non-weatherprotected locations
Classification des conditions d'environnement –
Partie 3-4: Classification des groupements des agents d'environnement et de
leurs sévérités – Utilisation à poste fixe, non protégé contre les intempéries
IEC 60721-3-4:2019-05(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60721-3-4
Edition 3.0 2019-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 3-4: Classification of groups of environmental parameters and their
severities – Stationary use at non-weatherprotected locations
Classification des conditions d'environnement –
Partie 3-4: Classification des groupements des agents d'environnement et de
leurs sévérités – Utilisation à poste fixe, non protégé contre les intempéries
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040 ISBN 978-2-8322-6956-5

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60721-3-4:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 General ........................................................................................................................... 6

5 Classification of groups of environmental parameters and their severities ........................ 7

5.1 General ................................................................................................................... 7

5.2 Climatic conditions (K) ............................................................................................ 7

5.3 Special climatic conditions (Z)................................................................................. 8

5.4 Biological conditions (B) ......................................................................................... 8

5.5 Chemically active substances (C) ........................................................................... 8

5.6 Mechanically active substances (S) ........................................................................ 8

5.7 Mechanical conditions (M) ...................................................................................... 8

(informative) Interdependence of air temperature, relative air humidity, and

absolute air humidity ............................................................................................................. 12

(informative) Definition of seismic environment ...................................................... 13

Bibliography .......................................................................................................................... 15

Figure A.1 – Climatogram of interdependence of air temperature, relative air humidity,

and absolute air humidity ...................................................................................................... 12

Table 1 – Classification of climatic conditions ......................................................................... 9

Table 2 – Classification of special climatic conditions .......................................................... 10

Table 3 – Classification of biological conditions .................................................................... 10

Table 4 – Classification of mechanically active substances ................................................... 10

Table 5 – Classification of mechanical conditions ................................................................. 11

Table B.1 – Correlation of seismic zones with expected magnitudes ..................................... 14

---------------------- Page: 4 ----------------------
IEC 60721-3-4:2019 © IEC 2019 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –
Part 3-4: Classification of groups of environmental parameters and
their severities – Stationary use at non-weatherprotected locations
FOREWORD

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60721-3-4 has been prepared by IEC technical committee 104:

Environmental conditions, classification, and methods of test.
This third edition cancels and replaces the second edition published in 1995 and
Amendment 1:1996. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) Clause 1: reworded.
b) Clause 2: normative references have been updated.
c) Clause 3: definitions have been updated.
d) Clause 4: reworded and simplified.
---------------------- Page: 5 ----------------------
– 4 – IEC 60721-3-4:2019 © IEC 2019

e) Clause 5: revised and updated. Several classes have been replaced by completely new

classes based on the use of new information obtained from referenced technical reports.

f) Defined values of chemically active substances are now by reference to ISO 9223.

g) Tables 1 through 5: updated.
The text of this International Standard is based on the following documents:
FDIS Report on voting
104/828/FDIS 104/836/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60721 series, published under the general title Classification of

environmental conditions, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 60721-3-4:2019 © IEC 2019 – 5 –
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –
Part 3-4: Classification of groups of environmental parameters and
their severities – Stationary use at non-weatherprotected locations
1 Scope

This part of IEC 60721 classifies groups of environmental parameters and their severities to

which products are subjected when installed for stationary use at non-weatherprotected

locations. Weatherprotected locations where products can be mounted for stationary use

permanently or temporarily are addressed in IEC 60721-3-3.

The environmental conditions specified in this document are limited to those which can

directly affect the performance of products. Only environmental conditions as such are

considered. No special description of the effects of these conditions on the products is

provided.

Environmental conditions directly related to fire or explosion hazards, microclimate within a

product, and conditions related to effects from ionizing radiation are excluded. Any other

unforeseen incidents are also excluded.

A limited number of classes of environmental conditions is given, covering a broad field of

application.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
stationary use

use of a product mounted firmly on a structure, or permanently placed at a certain site

3.2
non-weatherprotected location
location at which a product is not protected from meteorological conditions
3.3
sheltered location

location at which a product is covered by a structure to protect it from direct meteorological

conditions, i.e. direct sunlight, heavy rain
---------------------- Page: 7 ----------------------
– 6 – IEC 60721-3-4:2019 © IEC 2019
4 General

A product may be subjected to a range of environmental conditions during its lifetime. These

conditions have been separated into classes described in IEC 60721-3 (all parts). The classes

given may be used for defining the maximum short-term environmental stresses on a product.

However, they do not provide information regarding the long-term or total lifetime

environmental stresses a product may experience. This means that no reliability or lifetime

assessment is possible based on these classes alone. Refer to IEC 60721-2 (all parts) and

applicable technical reports (IEC TR 62130, IEC TR 62131-2, IEC TR 62131-3,

IEC TR 62131-4 and IEC TR 62131-5) for further information on actual environmental

conditions.

A product may be simultaneously exposed to several environmental parameters, for example,

solar radiation and temperature, temperature and humidity, as well as vibration and

temperature change. Combinations of the environmental parameters given may increase the

stress effect on a product. Therefore, combined conditions should be considered in the design

and evaluation of a product.

Products should be designed to survive and operate in different environments. Basically, they

will be affected by environmental influences in two ways:

– by the effects of short-term extreme environmental conditions which may directly cause

malfunction or destroy the product;

– by the effect of long-term subjection to non-extreme environmental stresses which may

slowly degrade the product and finally cause malfunction or destruction of the product.

Short-term extreme environmental conditions may occur at any time in a product's life. A

product may be unaffected by an extreme condition when it is new but fail when it is subjected

to the same condition after being used for a long period of time due to the effect of ageing.

The order in which the environmental conditions are applied may affect the results of an

evaluation.

It is important for the product specification, when referring to a certain class in IEC 60721-3

(all parts), to define whether the product is required to be capable of operating when being

exposed to the conditions described by the class.

The environmental classes may be used as a basis for the selection of design and test

severities with respect to the consequence of failure. Information contained in IEC 60721-3

(all parts) may be used to help establish expected requirements for use, storage,

transportation, etc., and in the development of relevant specifications. The selected severities

used for testing should attempt to produce the effects of the actual environment.

EXAMPLE 1 A high temperature test on a heat dissipating product is designed to simulate the thermal effect of

subjecting a product to conditions of high air temperature, solar radiation and other possible heat sources

dependent on the application.

EXAMPLE 2 In a mechanical shock test, the product can be subjected to mechanical shocks of simple pulse

shapes (e.g., half-sine), while the actual conditions cannot be described by such simple pulses.

It is recognized that extreme or special environmental conditions may exist which require

consideration of severities that are not addressed in this document. The user of this document

should select the lowest classification necessary for covering the conditions of the intended

use.
---------------------- Page: 8 ----------------------
IEC 60721-3-4:2019 © IEC 2019 – 7 –
5 Classification of groups of environmental parameters and their severities
5.1 General

Several classes for climatic conditions (K), special climatic conditions (Z), biological

conditions (B), chemically active substances (C), mechanically active substances (S), and

mechanical conditions (M) are specified.

This classification allows for several possible combinations of environmental conditions which

bear upon products when installed in non-weatherprotected locations. It represents the real

situation concerning world-wide conditions of use due to local influences of open-air climate,

etc.

For certain environmental parameters, it has not yet been possible to specify quantitative

severities.

For a given location or product, reference should be made to the total set of classes as

defined in 5.2 through 5.7, for example:
4K26/4Z3/4B3/4C2/4S12/4M10
5.2 Climatic conditions (K)

The classes defined in previous versions of this document have been replaced with new

classes as a result of recent efforts at collecting information regarding climatic conditions.

Those results are contained in technical reports referenced in this document.

At non-weatherprotected locations, the influence of special climatic conditions constitutes a

more significant share of the effects bearing upon a product and its functional parts than at

weatherprotected locations. Particularly the effects of temperature change, solar radiation,

precipitation, air velocity and wind-chill should be considered in this respect.

The severity of these effects may be influenced for instance by constructional details (sort

and thickness of material, colour of surface, sealing or breathing of casings or enclosures,

product heating, etc.) and by mounting details (selection of mounting site, consideration of

degree of exposure to prevailing wind and weather, etc.).

The climatic conditions specified for classes 4K23 to 4K27 refer to the non-weatherprotected

conditions where products may be used. These conditions have been experienced world-wide

over a long time period. The conditions should cover all normal cases, but not exceptional

events. These conditions are specified in Table 1. The interdependence of temperature to

relative humidity is shown in Annex A.
Sheltered non-weatherprotected locations

4K23 applies to sheltered non-weatherprotected locations in tropical, arid, temperate, and

cold climatic classification with the thermal effects from solar radiation encompassed

in the temperature.

4K24 applies to sheltered non-weatherprotected locations in the polar climate type with the

thermal effects from solar radiation encompassed in the temperature.
Open-air non-weatherprotected locations
4K25 applies to open-air locations in the tropical climatic classification.

4K26 applies to open-air storage in the arid and temperate climatic classifications.

4K27 applies to open-air storage in the cold and polar climatic classifications.
---------------------- Page: 9 ----------------------
– 8 – IEC 60721-3-4:2019 © IEC 2019
5.3 Special climatic conditions (Z)

Parameters such as heat radiation, movement of the surrounding air, solar radiation, snow

load, and water from sources other than rain may occur with any severity in combination with

any of the other climatic conditions. Recommended values for these conditions are shown in

Table 2.
5.4 Biological conditions (B)

No quantitative severity has been specified for the following conditions. The specified

parameters of Table 3 are typical, but may not be complete.

4B1 applies to locations where mould growth is prevented, and physical controls are in

place to prevent attack by animals.

4B2 applies to locations where no controls are in place to prevent mould growth or

attacks by animals, except termites.
4B3 applies to locations where attacks by termites or similar fauna may occur.
5.5 Chemically active substances (C)

The contamination of the natural atmosphere is mainly caused by chemical emissions from

industrial activities, motor-driven vehicles, and heating systems. A further chemical influence

is caused by aerosols of sea and road salts. Contamination may affect the function and

materials of products. Additional details regarding the categorization of these conditions may

be found in ISO 9223.
5.6 Mechanically active substances (S)

Dust and sand are classified together, as the effects caused by these environmental

conditions are similar.

4S10 applies to locations where precautions have been taken to minimize the presence of

dust and sand.

4S11 applies to locations not situated in proximity to dust or sand sources and with no

precautions to minimize the ingress of dust or sand.

4S12 applies to locations near sand or dust sources, including urban areas and with no

precautions to minimize the ingress of dust or sand. It also applies to locations

situated in areas not subject to natural dust storms or significant industrial activity.

4S13 applies to locations which may be exposed to wind-driven dust and sand either due

to natural conditions or due to industrial activity producing blown sand or dust.

These conditions are specified in Table 4.
5.7 Mechanical conditions (M)

Mechanical conditions relate to the levels of vibration and shock that may exist at a usage

location, for example as a result of normal operations, nearby vehicular movement. These

conditions are specified in Table 5. See Annex B for the definition of seismic environment.

4M10 applies to locations experiencing insignificant levels of vibration and shock.

4M11 applies to non-weatherprotected locations experiencing low levels of vibration and

shock, such as those transmitted from air conditioning, machines or passing vehicles

in the vicinity.

4M12 applies to non-weatherprotected locations experiencing significant levels of vibration

and shock, such as those close to heavy machines or conveyor belts.
---------------------- Page: 10 ----------------------
IEC 60721-3-4:2019 © IEC 2019 – 9 –
Table 1 – Classification of climatic conditions
Classification
Environmental parameter Unit Sheltered Open-air
4K23 4K24 4K25 4K26 4K27
°C +5 -50
Low air temperature −45 −50 −20
i i i
High air temperature °C +70 +70 +45 +50 +45
Low relative humidity % 4 4 30 4 10
High relative humidity % 100 100 100 100 100
a 3
Low absolute humidity g/m 0,2 0,003 6 0,1 0,003
a 3
High absolute humidity g/m 35 20 35 30 25
Rate of change of temperature °C/min 1,0 1,0 1,0 1,0 1,0
Low air pressure kPa 70 70 70 70 70
High air pressure kPa 106 106 106 106 106
2 h h l l l
Solar radiation W/m 1 090 1 090 1 090
f f
Heat radiation Not specified No No No
d d, f d, f f f f
Movement of surrounding air m/s 5,0 5,0 22 22 22
Condensation Not specified Yes Yes Yes Yes Yes
m g g
Precipitation (rain, snow, hail, etc.) Not specified Yes Yes Yes Yes Yes
g g
Rain intensity mm/min No No 15 15 15
Driving rain m/s No No 18 18 18
g g
Snow load kg/m No No No
e g g
Low rain temperature °C No No +5 +5 +5
j j j
Not specified Dripping Dripping
Water from sources other than rain
water water
k k k
Formation of ice and frost Not specified Yes Yes Yes Yes Yes

The low and high relative humidity levels are limited by the low and high absolute humidity. See Annex A.

Averaged over a period of 5 min.

The value of 70 kPa represents a limit for open-air conditions, normally at an altitude of 3 000 m. In some

geographical areas, open-air conditions may occur at higher altitudes. Conditions in mines are not considered.

If applicable, a special value may be selected from Table 2.

A cooling system based on non-assisted convection may be disturbed by adverse movement of surrounding

air.

This rain temperature should be considered together with high air temperature and solar radiation. The

cooling effect of the rain should be considered in connection with the surface temperature of the product.

If applicable, a special value may be selected from Table 2.
Applies only to wind-driven precipitation at sheltered locations.
Thermal effect of solar radiation is included in the temperature.
Thermal effect of solar radiation is not included in the temperature.
Sources of water other than rain are encompassed in driving rain.
Formation of frost can occur due to heat radiation to a clear sky.
From sea level.
See IEC 60721-2-2 for additional information.
---------------------- Page: 11 ----------------------
– 10 – IEC 60721-3-4:2019 © IEC 2019
Table 2 – Classification of special climatic conditions
Environmental parameter Class Unit Special condition Z
Heat radiation 4Z1 No Negligible
4Z2 No Conditions of heat radiation, for
example, near heating systems
Wind, steady state 4Z4 m/s 30
4Z5 m/s 50
4Z11 m/s 67
Water from sources other than rain 4Z12 No Dripping water
4Z13 No Spraying water
4Z14 No Splashing water
Solar radiation 4Z15 W/m 500
4Z16 W/m 700
Snow load 4Z17 kg/m 100 (single snow storm)
4Z18 kg/m 240 (whole season)
Air pressure 4Z10 kPa 84 (approx. 1 500 m above sea level)
4Z19 kPa 62 (approx. 4 000 m above sea level)
Velocities are 10-min averages taken at a height of 10 m above ground.
Table 3 – Classification of biological conditions
Class
Biological parameter
4B1 4B2 4B3
...

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