Petroleum products and other liquids — Guidance for flash point and combustibility testing

This document establishes an overview of test methods in the field to determine flash point and combustibility of petroleum and related products. It presents advice on application and specification development. This document is not intended to be a comprehensive manual on flash point and combustibility tests, and the interpretation of test results, however it covers the key aspects on these subjects.

Produits pétroliers et autres liquides — Lignes directrices pour les essais de combustibilité et de point d'éclair

General Information

Status
Published
Publication Date
24-Jun-2020
Current Stage
6060 - International Standard published
Start Date
29-Apr-2020
Completion Date
25-Jun-2020
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TECHNICAL ISO/TR
REPORT 29662
Second edition
2020-06
Petroleum products and other
liquids — Guidance for flash point and
combustibility testing
Produits pétroliers et autres liquides — Lignes directrices pour les
essais de combustibilité et de point d'éclair
Reference number
ISO/TR 29662:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO/TR 29662:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 29662:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3  Terms and definitions ..................................................................................................................................................................................... 1

4  Outline of generic definitions and general statements in test methods ....................................................2

5 Brief history ............................................................................................................................................................................................................... 2

6  Flash and fire point, and sustained combustion and burning .............................................................................. 3

7  Why are flash point and combustibility tests required ................................................................................................ 3

8 Which test method should be used ................................................................................................................................................... 4

8.1 First considerations ............................................................................................................................................................................ 4

8.2 Open or closed cup .............................................................................................................................................................................. 4

8.3 Non-equilibrium, equilibrium and rapid equilibrium tests ............................................................................. 4

8.3.1 General...................................................................................................................................................................................... 4

8.3.2 Non-equilibrium tests ................................................................................................................................................. 5

8.3.3 Equilibrium tests ............................................................................................................................................................. 5

8.3.4 Rapid equilibrium tests .............................................................................................................................................. 5

8.4 Flash point automation .................................................................................................................................................................... 5

8.4.1 Manual flash point test ............................................................................................................................................... 5

8.4.2 Automated flash point testers .............................................................................................................................. 5

8.5 Correlation between methods ................................................................................................................................................... 6

8.6 Precision ....................................................................................................................................................................................................... 6

8.7 Valid temperature ranges .............................................................................................................................................................. 6

9 Testing environment ........................................................................................................................................................................................ 6

10 Safety ................................................................................................................................................................................................................................ 7

11  Calibration and verification ...................................................................................................................................................................... 7

11.1 General ........................................................................................................................................................................................................... 7

11.2 Calibration .................................................................................................................................................................................................. 7

11.3 Verification ................................................................................................................................................................................................. 8

12 Test samples .............................................................................................................................................................................................................. 8

12.1 Sample handling .................................................................................................................................................................................... 8

12.2 Samples containing volatile flammable components ............................................................................................ 8

12.3 Viscous and semi-solid samples ............................................................................................................................................... 8

12.4 Biodiesel (B100 FAME- Fatty Acid Methyl Ester)...................................................................................................... 9

12.5 Mixtures of materials ......................................................................................................................................................................... 9

12.6 Samples that form a skin during testing ........................................................................................................................... 9

13 Instrumentation .................................................................................................................................................................................................... 9

13.1 Ignition sources ...................................................................................................................................................................................... 9

13.2 Flash detection .....................................................................................................................................................................................10

13.3 Stirring ........................................................................................................................................................................................................10

13.4 Temperature measurement ......................................................................................................................................................10

13.5 Care of the instrument...................................................................................................................................................................11

13.6 Sub ambient testing .........................................................................................................................................................................11

14 Flash point testing effects ........................................................................................................................................................................11

15 Test results ...............................................................................................................................................................................................................12

15.1 Barometric pressure correction ............................................................................................................................................12

15.2 Expression and reporting of results ..................................................................................................................................13

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/TR 29662:2020(E)

Annex A (informative) Major test methods used in specifications and regulations ........................................14

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

iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TR 29662:2020(E)
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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels

and lubricants from natural or synthetic sources.

This second edition cancels and replaces the first edition (ISO 29662:2009). The main technical changes

compared to the previous edition are as follows:
— the title has been changed;
— combustibility test details have been further added;
— a list of examples of regulations have been added;

— test samples, to include biodiesel, mixtures and samples that form a skin during testing have

been added;
— the use of low hazard glass thermometers has been added;

— further details regarding the requirements for barometric corrections have been added;

— Annex A has been added to include temperature ranges for each test method.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/TR 29662:2020(E)
Introduction

This document was written to assist laboratory managers and technicians, regulators, specification

writers and industry in the use, specification and application of flash point and combustibility tests for

liquids and semi-solids.

The flash point test can be summarised as a procedure where a test portion is introduced into a

temperature-controlled test cup and an ignition source is applied to the vapours produced by the test

portion to determine if the vapour / air mixture is flammable or at what temperature the vapour / air

mixture is flammable.

Combustibility tests in this document comprise fire point, sustained combustibility and sustained

burning tests. These tests can be summarised as a procedure where a test portion is introduced into a

temperature-controlled test cup and an ignition source is applied to the vapours produced by the test

portion to determine if the vapour / air mixture catches fire and continues to burn.

This document was developed by the Joint ISO/TC 28 - ISO/TC 35 WG9 on flash point methods.

vi © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
TECHNICAL REPORT ISO/TR 29662:2020(E)
Petroleum products and other liquids — Guidance for flash
point and combustibility testing
1 Scope

This document establishes an overview of test methods in the field to determine flash point and

combustibility of petroleum and related products. It presents advice on application and specification

development. This document is not intended to be a comprehensive manual on flash point and

combustibility tests, and the interpretation of test results, however it covers the key aspects on these

subjects.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 1998-1, Petroleum industry — Terminology — Part 1: Raw materials and products

ISO 1998-2, Petroleum industry — Terminology — Part 2: Properties and tests
3  Terms and definitions

For the purposes of this document, the terms and definitions in ISO 1998-1 and ISO 1998-2 and the

following apply.

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

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
repeatability

difference between two test results obtained by the same operator with the same apparatus under

constant operating conditions, on identical test material would, in the long run and in the normal

operation of the test method, exceed the given value in only one case in 20

Note 1 to entry: The general description deviates from ISO 4259-1 used in many of the standards dealt with in

this document.
3.2
reproducibility

difference between two single and independent test results obtained by different operators in different

laboratories on identical test material that would, in the long run and in the normal operation of the

test method, exceed the given value in only one case in 20

Note 1 to entry: The general description deviates from ISO 4259-1 used in many of the standards dealt with in

this document.
© ISO 2020 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO/TR 29662:2020(E)
4  Outline of generic definitions and general statements in test methods

4.1 There are many, slightly different, definitions of flash point, however the following definition is

widely used in standard test methods:

The lowest temperature of the test portion, adjusted to account for variations in atmospheric pressure

from 101,3 kPa, at which application of an ignition source causes the vapour of the test portion to ignite

and the flame to propagate across the surface of the liquid under the specified conditions of test.

4.2 It is important to realise that the value of the flash point is not a physical constant but it is the result

of a flash point test and is dependent on the apparatus and procedure used. This fact is so important that

a general statement similar to the following is incorporated into all the main flash point methods:

Flash point values are not a constant physical-chemical property of materials tested. They are a

function of the apparatus design, the condition of the apparatus used, and the operational procedure

carried out. Flash point can therefore only be defined in terms of a standard test method, and no general

valid correlation can be guaranteed between results obtained by different test methods or with test

apparatus different from that specified.
4.3 Combustibility tests have their own definitions, the following are examples.

— Sustained combustibility: behaviour of a material, under specified test conditions, whereby its

vapour can be ignited by an ignition source and, after ignition, sufficient flammable vapour is

produced for burning to continue for at least 15 s after the source of ignition has been removed.

— Fire point: lowest temperature of the test portion, adjusted to account for variations in atmospheric

pressure from 101,3 kPa, at which application of a test flame causes the vapour of the test portion

to ignite and sustain burning for a minimum of 5 s under the specified conditions of test.

— The sustained burning test does not have a formal definition, however, it may be defined as follows:

behaviour of a material, under specified test conditions, whereby its vapour can be ignited by an

ignition source and, after ignition, sufficient flammable vapour is produced for burning to continue

for at least 15 s after the source of ignition has been removed.

NOTE All flash point and combustibility test temperatures are corrected by a formula that compensates if

the barometric pressure is not 101,3 kPa.

4.4 Due to the importance of flash point and combustibility test results for both safety and regulatory

purposes, the test method identification should always be included with the test result.

4.5 In general specific products specifications indicate which standard test method should be

employed.
5 Brief history

5.1 The discovery of petroleum and the increased use of flammable distillates in the 19 century, for

lighting and heating in place of animal and vegetable oils, led to a large number of explosions and other

fire related accidents.

Legislation, such as the UK Petroleum Act in 1862 and the German Petroleum Regulations in 1882,

quickly spread around the world and led to the development of many types of test instruments.

The following list shows the dates when the major surviving instruments were in a form probably

recognisable today:
— 1870 – 1880: Abel closed cup, Pensky-Martens closed cup;
— 1910 – 1920: Tag closed cup, Cleveland open cup.
2 © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/TR 29662:2020(E)

5.2 Flash point and combustibility tests are key components of transport, safety and health regulations.

The examples of such regulations shown below are used in Europe but have numerous equivalents

internationally. These regulations have been used in the past to assist in setting specification levels for

flash point requirements.
DSD Dangerous substances directive – 2015 replaced by CLP
DPD Dangerous preparations directive – 2015 replaced by CLP
CLP Classification, labelling and packaging
ADR Carriage of dangerous goods by road
GHS Global harmonized system – classification, labelling and packaging
ADN Carriage of dangerous goods by inland waterways
RID Carriage of dangerous goods by rail
6  Flash and fire point, and sustained combustion and burning

6.1 The flash point is essentially the lowest temperature of the liquid or semi-solid at which vapours

from a test portion combine with air to give a flammable mixture and ‘flash’ when an ignition source is

applied. Fire point, combustibility and sustained burning tests all use open cup instruments.

6.2 Fire point can be considered as the lowest temperature of the test portion at which vapour

combustion and burning commences when an ignition source is applied and thereafter is continuous and

where the heat produced is self-sustaining and supplies enough vapours to combine with air and burn

even after the removal of the ignition source.

6.3 Sustained combustion and burning tests are usually carried out with the test portion at a fixed

temperature and tests whether vapour combustion and burning commences when an ignition source is

applied and thereafter is continuous and where the heat produced is self-sustaining and supplies enough

vapours to combine with air and burn even after the removal of the ignition source.

7  Why are flash point and combustibility tests required

The fundamental reason for the requirement of flash point measurements is to assess the safety hazard

of a liquid or semi-solid with regard to its flammability and then classify the liquid into a group. The

lower the flash point temperature the greater the risk. This classification is then used to warn of a risk

and to enable the correct precautions to be taken when using, storing or transporting the liquid.

Specifications quote flash point values for quality control purposes as well as for controlling the

flammability risk.

A change in flash point can indicate the presence of potentially dangerous volatile contaminants or the

adulteration of one product by another.

Test methods that enable the ability of a liquid to support a sustained combustion flame to be assessed,

offer a means of further identifying the hazard of liquids under possible fire conditions for use in safety

and health regulation classifications.
© ISO 2020 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO/TR 29662:2020(E)
8 Which test method should be used
8.1 First considerations

Firstly, if a specific test method has been specified in a product specification or regulation, then that

method should be the first choice. If a number of alternative methods are specified then the choice

is influenced by availability and other factors such as sample size requirements, speed of testing or

precision. In certain circumstances the choice of the stated referee method is of special importance.

Annex A gives an overview of the most common methods and their use in specifications and regulations.

When testing specifically for contamination or contaminants, certain test methods and procedures

are more appropriate than others. In general, an equilibrium test method is recommended for testing

samples that can contain traces of volatile contaminants.

When selecting a flash point method for incorporation into a product specification or regulation, it is

important that the product type is included in the scope of the test method and that the temperature

range of the product is covered by the test method. If the product is not included in the scope then the test

can be unsuitable for the product or the quoted precision does not apply. Where the scope of a test method

is general or not suitable it is recommended to contact an appropriate standardization body for advice.

When testing chemicals, mineral products or corrosive materials, it is recommended to check that

the test cup material is suitable and will not produce flammable gases or be damaged by any possible

chemical reaction.

The use of the sustained combustibility test is implemented in some safety and health regulations and

can be useful for some products to obtain an alternative hazard classification.
8.2 Open or closed cup
There are two general classes of flash point tests: open cup and closed cup.

The open cup was initially developed to assess the potential hazards of liquid spillage. In this test, a

test portion of the sample is introduced into a cup that is open at the top. An ignition source is passed

horizontally over the surface of the liquid, while the cup and liquid are being heated, to test if the vapours

‘flash’. If the test is repeated at increasing test portion temperatures a point can be reached when the

test portion continues to burn without further application of the ignition source, this is the fire point.

The precision of open cup tests is somewhat poorer than closed cup tests as the vapours produced by

heating the test portion are free to escape to the atmosphere and are more affected by local conditions

in the laboratory. When open cup tests are made at temperatures above ambient temperature, the

result is usually higher than a result from a closed cup test due to the reduced concentration of vapours.

The closed cup test contains any vapours produced and essentially simulates the situation where a

potential source of ignition is accidentally introduced into a container. In this test, a test portion is

introduced into a cup and a close fitting lid is fitted to the top of the cup. The cup and test portion is

heated and apertures are then opened in the lid to allow air into the cup and the ignition source to be

dipped into the vapours to test for a flash.

The closed cup test predominates in specifications and regulations due to its better precision and

ability to detect contaminants.

Fire point, sustained combustion and sustained burning tests outlined in this technical report are all

open cup type tests.
8.3  Non-equilibrium, equilibrium and rapid equilibrium tests
8.3.1 General

These three types of tests and associated instruments are characterised by the level of temperature

stabilisation of the test portion and resultant vapours, and by the test portion size and test time.

4 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/TR 29662:2020(E)
8.3.2 Non-equilibrium tests

Test methods such as Pensky-Martens, Tag, Abel and Cleveland are referred to as non-equilibrium

tests as the test temperature of the test portion is increased during the test and the temperature of the

vapours is not the same (not in equilibrium) as the test portion temperature when the ignition source is

dipped at regular intervals into the cup.

This type of test has the advantage that it produces a definitive flash point result. Under normal

circumstances, the increasing temperature is not a problem, but when volatile contaminants or

components are present the short time between each dip of the ignition source, combined with the

rate of temperature increase, does not allow enough time for flammable vapours to evolve and this

can cause unreliable results. For this reason, non-equilibrium tests with lower rates of heating usually

perform better than those using higher rates of heating, when volatile contaminants or components are

present in the test portion.
8.3.3 Equilibrium tests

Equilibrium tests are preferred for liquids and semi-solids containing volatile components or

contaminants and for confirmatory purposes in regulations as the sample temperature is constant or

is increased at a very slow rate. This allows enough time for vapours to build up and for the vapours to

be in equilibrium with the test portion before the ignition source is dipped into the cup. The ignition

source is dipped in the cup at different test portion temperatures thus resulting in a measurement

of a flash point, or the ignition source is dipped only once to carry out a flash no flash test to check

conformity with specifications and flammability criteria.

These equilibrium tests use any type of closed cup in a liquid bath and limits the difference of

temperature between the test portion and the liquid bath. The liquid bath is specified because it gives

a very even temperature distribution on the outside of the test cup thus ensuring that hot spots are not

present on the cup surface that could cause the localised increase of flammable vapours and thus a low

flash point. Unfortunately, these procedures take a long time to complete.
...

TECHNICAL ISO/TR
REPORT 29662
Second edition
Petroleum products and other
liquids — Guidance for flash point
testing
Produits pétroliers et autres liquides — Lignes directrices pour la
détermination du point d'éclair
Member bodies are requested to consult relevant national interests in ISO/TC
35 before casting their ballot to the e-Balloting application.
PROOF/ÉPREUVE
Reference number
ISO/TR 29662:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO/TR 29662:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 29662:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3  Terms and definitions ..................................................................................................................................................................................... 1

4  Outline of generic definitions and general statements in test methods ....................................................2

5 Brief history ............................................................................................................................................................................................................... 2

6  Flash and fire point, and sustained combustion and burning .............................................................................. 3

7  Why are flash point and combustibility tests required ................................................................................................ 3

8  Which test method should be used ................................................................................................................................................... 4

8.1 First considerations ............................................................................................................................................................................ 4

8.2 Open or closed cup .............................................................................................................................................................................. 4

8.3 Non-equilibrium, equilibrium and rapid equilibrium tests ............................................................................. 4

8.3.1 General...................................................................................................................................................................................... 4

8.3.2 Non-equilibrium tests ................................................................................................................................................. 5

8.3.3 Equilibrium tests ............................................................................................................................................................. 5

8.3.4 Rapid equilibrium tests .............................................................................................................................................. 5

8.4 Flash point automation .................................................................................................................................................................... 5

8.4.1 Manual flash point test ............................................................................................................................................... 5

8.4.2 Automated flash point testers .............................................................................................................................. 5

8.5 Correlation between methods ................................................................................................................................................... 6

8.6 Precision ....................................................................................................................................................................................................... 6

8.7 Valid temperature ranges .............................................................................................................................................................. 6

9 Testing environment ........................................................................................................................................................................................ 6

10 Safety ................................................................................................................................................................................................................................ 7

11  Calibration and verification ...................................................................................................................................................................... 7

11.1 General ........................................................................................................................................................................................................... 7

11.2 Calibration .................................................................................................................................................................................................. 7

11.3 Verification ................................................................................................................................................................................................. 8

12 Test samples .............................................................................................................................................................................................................. 8

12.1 Sample handling .................................................................................................................................................................................... 8

12.2 Samples containing volatile flammable components ............................................................................................ 8

12.3 Viscous and semi-solid samples ............................................................................................................................................... 8

12.4 Biodiesel (B100 FAME- Fatty Acid Methyl Ester)...................................................................................................... 9

12.5 Mixtures of materials ......................................................................................................................................................................... 9

12.6 Samples that form a skin during testing ........................................................................................................................... 9

13 Instrumentation .................................................................................................................................................................................................... 9

13.1 Ignition sources ...................................................................................................................................................................................... 9

13.2 Flash detection .....................................................................................................................................................................................10

13.3 Stirring ........................................................................................................................................................................................................10

13.4 Temperature measurement ......................................................................................................................................................10

13.5 Care of the instrument...................................................................................................................................................................11

13.6 Sub ambient testing .........................................................................................................................................................................11

14 Flash point testing effects ........................................................................................................................................................................11

15 Test results ...............................................................................................................................................................................................................12

15.1 Barometric pressure correction ............................................................................................................................................12

15.2 Expression and reporting of results ..................................................................................................................................13

© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO/TR 29662:2020(E)

Annex A (informative) Major test methods used in specifications and regulations ........................................14

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

iv PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TR 29662:2020(E)
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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels

and lubricants from natural or synthetic sources.

This second edition cancels and replaces the first edition (ISO 29662:2009). The main technical changes

compared to the previous edition are as follows:
— the title has been changed;
— combustibility test details have been further added;
— a list of examples of regulations have been added;

— test samples, to include biodiesel, mixtures and samples that form a skin during testing have

been added;
— the use of low hazard glass thermometers has been added;

— further details regarding the requirements for barometric corrections have been added;

— Annex A has been added to include temperature ranges for each test method.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2020 – All rights reserved PROOF/ÉPREUVE v
---------------------- Page: 5 ----------------------
ISO/TR 29662:2020(E)
Introduction

This document was written to assist laboratory managers and technicians, regulators, specification

writers and industry in the use, specification and application of flash point and combustibility tests for

liquids and semi-solids.

The flash point test can be summarised as a procedure where a test portion is introduced into a

temperature-controlled test cup and an ignition source is applied to the vapours produced by the test

portion to determine if the vapour / air mixture is flammable or at what temperature the vapour / air

mixture is flammable.

Combustibility tests in this document comprise fire point, sustained combustibility and sustained

burning tests. These tests can be summarised as a procedure where a test portion is introduced into a

temperature-controlled test cup and an ignition source is applied to the vapours produced by the test

portion to determine if the vapour / air mixture catches fire and continues to burn.

This document was developed by the Joint ISO/TC 28 - ISO/TC 35 WG9 on flash point methods.

vi PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
TECHNICAL REPORT ISO/TR 29662:2020(E)
Petroleum products and other liquids — Guidance for flash
point testing
1 Scope

This document establishes an overview of test methods in the field to determine flash point and

combustibility of petroleum and related products. It presents advice on application and specification

development. This document is not intended to be a comprehensive manual on flash point and

combustibility tests, and the interpretation of test results, however it covers the key aspects on these

subjects.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 1998-1, Petroleum industry — Terminology —Part 1: Raw materials and products
ISO 1998-2, Petroleum industry — Terminology — Part 2: Properties and tests
3  Terms and definitions

For the purposes of this document, the terms and definitions in ISO 1998-1 and ISO 1998-2 and the

following apply.

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

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
repeatability

difference between two test results obtained by the same operator with the same apparatus under

constant operating conditions, on identical test material would, in the long run and in the normal

operation of the test method, exceed the given value in only one case in 20

Note 1 to entry: The general description deviates from ISO 4259-1 used in many of the standards dealt with in

this document.
3.2
reproducibility

difference between two single and independent test results obtained by different operators in different

laboratories on identical test material that would, in the long run and in the normal operation of the

test method, exceed the given value in only one case in 20

Note 1 to entry: The general description deviates from ISO 4259-1 used in many of the standards dealt with in

this document.
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4  Outline of generic definitions and general statements in test methods

4.1 There are many, slightly different, definitions of flash point, however the following definition is

widely used in standard test methods:

The lowest temperature of the test portion, adjusted to account for variations in atmospheric pressure

from 101,3 kPa, at which application of an ignition source causes the vapour of the test portion to ignite

and the flame to propagate across the surface of the liquid under the specified conditions of test.

4.2 It is important to realise that the value of the flash point is not a physical constant but it is the result

of a flash point test and is dependent on the apparatus and procedure used. This fact is so important that

a general statement similar to the following is incorporated into all the main flash point methods:

Flash point values are not a constant physical-chemical property of materials tested. They are a

function of the apparatus design, the condition of the apparatus used, and the operational procedure

carried out. Flash point can therefore only be defined in terms of a standard test method, and no general

valid correlation can be guaranteed between results obtained by different test methods or with test

apparatus different from that specified.
4.3 Combustibility tests have their own definitions, the following are examples.

— Sustained combustibility: behaviour of a material, under specified test conditions, whereby its

vapour can be ignited by an ignition source and, after ignition, sufficient flammable vapour is

produced for burning to continue for at least 15 s after the source of ignition has been removed.

— Fire point: lowest temperature of the test portion, adjusted to account for variations in atmospheric

pressure from 101,3 kPa, at which application of a test flame causes the vapour of the test portion

to ignite and sustain burning for a minimum of 5 s under the specified conditions of test.

— The sustained burning test does not have a formal definition, however, it may be defined as follows:

behaviour of a material, under specified test conditions, whereby its vapour can be ignited by an

ignition source and, after ignition, sufficient flammable vapour is produced for burning to continue

for at least 15 s after the source of ignition has been removed.

NOTE All flash point and combustibility test temperatures are corrected by a formula that compensates if

the barometric pressure is not 101,3 kPa.

4.4 Due to the importance of flash point and combustibility test results for both safety and regulatory

purposes, the test method identification should always be included with the test result.

4.5 In general specific products specifications indicate which standard test method should be

employed.
5 Brief history

5.1 The discovery of petroleum and the increased use of flammable distillates in the 19 century, for

lighting and heating in place of animal and vegetable oils, led to a large number of explosions and other

fire related accidents.

Legislation, such as the UK Petroleum Act in 1862 and the German Petroleum Regulations in 1882,

quickly spread around the world and led to the development of many types of test instruments.

The following list shows the dates when the major surviving instruments were in a form probably

recognisable today:
— 1870 – 1880: Abel closed cup, Pensky-Martens closed cup;
— 1910 – 1920: Tag closed cup, Cleveland open cup.
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5.2 Flash point and combustibility tests are key components of transport, safety and health regulations.

The examples of such regulations shown below are used in Europe but have numerous equivalents

internationally. These regulations have been used in the past to assist in setting specification levels for

flash point requirements.
DSD Dangerous substances directive – 2015 replaced by CLP
DPD Dangerous preparations directive – 2015 replaced by CLP
CLP Classification, labelling and packaging
ADR Carriage of dangerous goods by road
GHS Global harmonized system – classification, labelling and packaging
ADN Carriage of dangerous goods by inland waterways
RID Carriage of dangerous goods by rail
6  Flash and fire point, and sustained combustion and burning

6.1 The flash point is essentially the lowest temperature of the liquid or semi-solid at which vapours

from a test portion combine with air to give a flammable mixture and ‘flash’ when an ignition source is

applied. Fire point, combustibility and sustained burning tests all use open cup instruments.

6.2 Fire point can be considered as the lowest temperature of the test portion at which vapour

combustion and burning commences when an ignition source is applied and thereafter is continuous and

where the heat produced is self-sustaining and supplies enough vapours to combine with air and burn

even after the removal of the ignition source.

6.3 Sustained combustion and burning tests are usually carried out with the test portion at a fixed

temperature and tests whether vapour combustion and burning commences when an ignition source is

applied and thereafter is continuous and where the heat produced is self-sustaining and supplies enough

vapours to combine with air and burn even after the removal of the ignition source.

7  Why are flash point and combustibility tests required

The fundamental reason for the requirement of flash point measurements is to assess the safety hazard

of a liquid or semi-solid with regard to its flammability and then classify the liquid into a group. The

lower the flash point temperature the greater the risk. This classification is then used to warn of a risk

and to enable the correct precautions to be taken when using, storing or transporting the liquid.

Specifications quote flash point values for quality control purposes as well as for controlling the

flammability risk.

A change in flash point can indicate the presence of potentially dangerous volatile contaminants or the

adulteration of one product by another.

Test methods that enable the ability of a liquid to support a sustained combustion flame to be assessed,

offer a means of further identifying the hazard of liquids under possible fire conditions for use in safety

and health regulation classifications.
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8  Which test method should be used
8.1 First considerations

Firstly, if a specific test method has been specified in a product specification or regulation, then that

method should be the first choice. If a number of alternative methods are specified then the choice

is influenced by availability and other factors such as sample size requirements, speed of testing or

precision. In certain circumstances the choice of the stated referee method is of special importance.

Annex A gives an overview of the most common methods and their use in specifications and regulations.

When testing specifically for contamination or contaminants, certain test methods and procedures

are more appropriate than others. In general, an equilibrium test method is recommended for testing

samples that can contain traces of volatile contaminants.

When selecting a flash point method for incorporation into a product specification or regulation, it is

important that the product type is included in the scope of the test method and that the temperature

range of the product is covered by the test method. If the product is not included in the scope then the test

can be unsuitable for the product or the quoted precision does not apply. Where the scope of a test method

is general or not suitable it is recommended to contact an appropriate standardization body for advice.

When testing chemicals, mineral products or corrosive materials, it is recommended to check that

the test cup material is suitable and will not produce flammable gases or be damaged by any possible

chemical reaction.

The use of the sustained combustibility test is implemented in some safety and health regulations and

can be useful for some products to obtain an alternative hazard classification.
8.2 Open or closed cup
There are two general classes of flash point tests: open cup and closed cup.

The open cup was initially developed to assess the potential hazards of liquid spillage. In this test, a

test portion of the sample is introduced into a cup that is open at the top. An ignition source is passed

horizontally over the surface of the liquid, while the cup and liquid are being heated, to test if the vapours

‘flash’. If the test is repeated at increasing test portion temperatures a point can be reached when the

test portion continues to burn without further application of the ignition source, this is the fire point.

The precision of open cup tests is somewhat poorer than closed cup tests as the vapours produced by

heating the test portion are free to escape to the atmosphere and are more affected by local conditions

in the laboratory. When open cup tests are made at temperatures above ambient temperature, the

result is usually higher than a result from a closed cup test due to the reduced concentration of vapours.

The closed cup test contains any vapours produced and essentially simulates the situation where a

potential source of ignition is accidentally introduced into a container. In this test, a test portion is

introduced into a cup and a close fitting lid is fitted to the top of the cup. The cup and test portion is

heated and apertures are then opened in the lid to allow air into the cup and the ignition source to be

dipped into the vapours to test for a flash.

The closed cup test predominates in specifications and regulations due to its better precision and

ability to detect contaminants.

Fire point, sustained combustion and sustained burning tests outlined in this technical report are all

open cup type tests.
8.3  Non-equilibrium, equilibrium and rapid equilibrium tests
8.3.1 General

These three types of tests and associated instruments are characterised by the level of temperature

stabilisation of the test portion and resultant vapours, and by the test portion size and test time.

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8.3.2  Non-equilibrium tests

Test methods such as Pensky-Martens, Tag, Abel and Cleveland are referred to as non-equilibrium

tests as the test temperature of the test portion is increased during the test and the temperature of the

vapours is not the same (not in equilibrium) as the test portion temperature when the ignition source is

dipped at regular intervals into the cup.

This type of test has the advantage that it produces a definitive flash point result. Under normal

circumstances, the increasing temperature is not a problem, but when volatile contaminants or

components are present the short time between each dip of the ignition source, combined with the

rate of temperature increase, does not allow enough time for flammable vapours to evolve and this

can cause unreliable results. For this reason, non-equilibrium tests with lower rates of heating usually

perform better than those using higher rates of heating, when volatile contaminants or components are

present in the test portion.
8.3.3  Equilibrium tests

Equilibrium tests are preferred for liquids and semi-solids containing volatile components or

contaminants and for confirmatory purposes in regulations as the sample temperature is constant or

is increased at a very slow rate. This allows enough time for vapours to build up and for the vapours to

be in equilibrium with the test portion before the ignition source is dipped into the cup. The ignition

source is dipped in the cup at different test portion temperatures thus resulting in a measurement

of a flash point, or the ignition source is dipped only once to carry out a flash no flash test to check

conformity with specifications and flammability criteria.

These equilibrium tests use any type of closed cup in a liquid bath and limits the difference of

temperature between the test portion and the liquid bath. The liquid bath is specified because it gives

a very even temperature distribution on the outsi
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