DOC

Guidance for classification of flammable liquids

By Bill Stephens,2014-05-12 05:02
12 views 0
Guidance for classification of flammable liquids

    ECBI/23/04

Draft 2004-01-30

Guidance for classification of flammable liquids

x.1 Properties

    Liquids that have a flashpoint of 93?C or less are subject to the hazard class flammable liquids. The

    flashpoint is the lowest temperature of the liquid, corrected to a barometric pressure of 101,3 kPa, at which

    application of a test flame causes the vapour of the liquid to ignite momentarily and a flame to propagate

    across the surface of the liquid under the specified conditions of test. This means, the lower explosion limit is

    exceeded at the flashpoint.

    x.2 Classification

    According to the classification criteria of GHS the flammable liquid is classified in one of four hazard

    categories (see GHS chapter 2.6).

    x.3 Classification tests

    x.3.1 Boiling point, initial boiling point

    Suitable methods for determining the (initial) boiling point are given in Directive 67/548 EWG, Appendix V,

    A2.

    x.3.2 Flashpoint

    x.3.2.1 General 1Flashpoints determined by testing or from internationally recognised qualified literature are to be preferred

    over those derived by calculation. Calculation should work for pure liquids, neglecting impurities, if the

    vapour pressure curve and lower explosion limit are accurately known. For mixtures, calculation of the

    flashpoint is sometimes not reliable and at this time, it is not possible to predict what reliance can be placed

    on a calculated value. Calculation can be used as a screening test for mixtures. If the method cited in GHS,

    chapter 2.6.4.2.3 is used for screening, the restrictions outlined in the GHS, chapter 2.6.4.2.2 (a), (c), (d),

    should be observed; in addition, it must be ensured that the vapour pressure curves, the lower explosion

    limits and their temperature dependence are accurately known.

    Flashpoint shall be measured using standardized equilibrium or non-equilibrium methods. Normally a closed-

    cup method shall be used. The laboratory performing the tests should have an appropriate quality

    management system in operation. Test results from open-cup measurements may be acceptable only in

    special cases with an explicit justification.

    For classification purposes it is recommended to use the mean of at least two test runs. One of these runs

    may be automated. The finding should be verified in a test with manual observation. In case of a deviation

    beyond the tolerance limits of the method, the test shall be repeated with manual observation.

    If the flashpoint is found to be within ? 2 K a cut-off limit when using a non-equilibrium method, the determi-

    nation has to be repeated with an equilibrium method.

    Suitable methods are:

    Equilibrium methods non-equilibrium methods

     (EN) ISO 3679 EN ISO 13736

     (EN) ISO 3680 EN ISO 2719

     EN ISO 1516 DIN 51755

     EN ISO 1523 EN 456

     ASTM D 56

    Non-equilibrium methods normally do not reach a state of temperature and concentration equilibrium in the

    vapour phase unless the flashpoint is within ? 2 K of ambient temperature.

    Equilibrium methods are deemed to reach temperature and concentration equilibrium in the vapour phase.

    Irrespective of the method being used, the following effects can be seen during the determination:

    Table 1: Special observations and possible interpretations

    A halo appears around the ignition source The flashpoint is very near and just above the test

    temperature The liquid ignites and continues to burn instead of The flashpoint is significantly below the test igniting momentarily temperature The ignition flame does not enter the vapour phase a)The flashpoint is significantly below the test (the glowing intensity of the wire is changing) temperature.

    b)The vapour concentration is above the upper

    explosion limit.

     1 E. g. Database CHEMSAFE

The ignition flame is extinguished resp. blown out a) The flashpoint is significantly below the test

    (the glowing intensity of the wire is changing) when temperature

    carrying out a test b) A halogenated compound is under test

    c) The liquid may contain inerting compounds

    The flashpoint is much lower than expected The liquid may contain volatile compounds

    The method to be used shall be chosen taking into account the properties of the liquid and the scope of the standard:

    When using automated equipment to test liquids or liquid mixtures whose flash is very pale, special care has to be taken. It has to be ensured that automated and manual equipment give the same result for such liquids.

x.3.2.2 Non-halogenated liquid substances:

    For pure substances, the flashpoint is usually found 80 K to 120 K below the boiling point.

    Special care must be taken when a sample contains impurities with a lower boiling point than the main compound. Even if their concentration is below 0,5% (especially if their boiling point is substantially lower), they may have a strong effect on the test result. Impurities with a higher boiling point will normally have no effect on the flashpoint.

    Within the scope of the measurement norm, every standard is applicable.

x.3.2.3 Mixtures containing neither halogenated nor inert compounds:

    Non-viscous mixtures:

    - The flashpoint may be lower than the lowest flashpoint of the components.

    - Allowing for the scope of the norm, every standard is applicable, however, the following restrictions apply:

     -If the boiling points of the components of the mixture cover a wide range or their concentrations are very different, use of an equilibrium method is advised as this takes into account the effect these have on the composition of the vapour phase.

    - If the mixture tends to form a skin, care must be taken to ensure that a skin does not form during the test. Viscous mixtures

    - The flashpoint may be lower than the lowest flashpoint of the components.

    - Test methods with high heating rates (5 K to 6 K per min.) are not advised.

    - Test methods using a stirrer are to be preferred.

    - Non-volatile components may influence the flashpoint.

    - If the mixture tends to form a skin, care must be taken to ensure that a skin does not form during the test; (EN) ISO 3679 is advised.

    - If the boiling points of the components of the mixture cover a wide range of temperatures or their concentrations are very different, use of an equilibrium method is advised as this takes into account the effect these have on to the composition of the vapour phase.

    - The solubility of the components may vary with the temperature.

    - The result may vary with the temperature at which the ignition trials are started.

x.3.2.4 Mixtures containing inerting compounds, but not halogenated compounds:

    Non-viscous mixtures:

    - If the inert compound is water, and the flammable components are miscible with water, at temperatures of about 80?C and higher the vapour phase in the test cup may be inerted, making a flashpoint no longer detectable. At temperatures above 100?C a flashpoint will not normally be detectable (in a closed cup test) irrespective of whether or not the liquids are miscible with water.

    - The flashpoint may be lower than the lowest flashpoint of the components.

    - Allowing for the scope of the measurement norm, every standard is applicable, however, the following restrictions apply:

    - If the boiling points of the components of the mixture cover a wide range of temperatures or their concentrations are very different, use of an equilibrium method is advised since this takes into account the effect these have on the composition of the vapour phase.

    - If the mixture tends to form a skin, care must be taken to ensure that a skin does not form during the test. - For waterborne paints etc. and mixtures behaving in a similar way, the only valid method is (EN) ISO 3679.

Viscous mixtures

    - If the inert compound is water, and the flammable components are miscible with water, at temperatures of about 80?C and higher the vapour phase in the test cup may be inerted, making a flashpoint no longer detectable. At temperatures above 100?C a flashpoint will not normally be detectable (in a closed cup test) irrespective of whether or not the liquids are miscible with water.

    - If the inert is a highly volatile compound and its concentration is low , the ignitability of the mixture may depend on the temperature at which the tests are started, because the solubility may vary with temperature. Temperature ranges may exist where the vapour phase is inerted and others where it is not. - The solubility of different volatile compounds may vary with temperature.

    - The flashpoint may be lower than the lowest flashpoint of the components.

    - Test methods with high heating rates (5 K to 6 K per min.) are not suitable

    - Test methods using a stirrer are to be preferred, except for waterborne paints etc. and mixtures behaving in a similar way. In this case, the only valid method is (EN) ISO 3679.

    - Non-volatile compounds may influence (raise) the flashpoint.

    - If the mixture tends to form a skin, care must be taken to ensure that a skin does not form during the test; use of (EN) ISO 3679 is advised.

    - If the components of the mixture have a wide range of boiling points or their concentrations are very different, use of an equilibrium method is advised as this takes into account the effect these have on the composition of the vapour phase.

    - The solubility of the components may vary with the temperature.

    - The result may vary with the temperature at which the ignition trials are started.

    x.3.2.6.Halogenated organic liquids, mixtures of and mixtures containing halogenated organic compounds

    For some, but not all, partly halogenated, compounds it is possible to determine their explosion limits although a flashpoint cannot be measured by one of the standards listed. Such partly halogenated compounds can form explosive vapour/air mixtures although they do not have a flashpoint. This effect depends on the nature of the halogen atom and the ratio of the number of halogen atoms to the number of carbon and hydrogen atoms in the molecule. The reason for this behaviour is the high quenching potential of halogen atoms combined with the inappropriate dimensions and unsuitable design of the various flash point cups and procedures that are not suitable for such substances.

    Because of these properties, the tests must be run under careful control with manual observation. Any unusual observation (see also table 1) shall be noted in the test report. Test results may be very difficult to reproduce. In such cases, the lowest value found shall be reported. If a flash is observed during the screening run but not in the main trial performed in accordance with the standard, that value shall be mentioned in the test report with an appropriate note. Especially with mixtures containing low amounts of volatile halogenated compounds, the use of equilibrium methods may give a false negative result because the compound will be able to escape during the long waiting time before the test flame is applied. If the mixture contains low amounts of highly volatile halogenated compounds the ignitability may depend on the temperature range the tests are started, because the solubility may vary with temperature. Therefore temperature ranges may exist where the vapour phase is inerted and others where it is not because the highly volatile halogenated compound is more or less completely dissolved respectively escaped. The solubility of the components may vary with the temperature.

    The result may vary with the temperature at which the ignition trials are started especially when viscous mixtures are under test.

x.3.3 Self-sustained combustion

    Liquids classified as category 3 (23?C < flashpoint < 60?C) may be regarded as non-flammable liquids if

    negative results have been obtained in the sustained combustability test ISO 9038 at test temperatures of 60?C and 75 ?C.

Report this document

For any questions or suggestions please email
cust-service@docsford.com