ASTM E1232-91(1996)
(Test Method)Standard Test Method for Temperature Limit of Flammability of Chemicals
Standard Test Method for Temperature Limit of Flammability of Chemicals
SCOPE
1.1 This test method covers the determination of the minimum temperature at which vapors in equilibrium with a liquid (or solid) chemical will be sufficiently concentrated to form flammable mixtures in air at atmospheric pressure. This test method is written specifically for determination of the temperature limit of flammability of systems using air as the source of oxidant and diluent. It may also be used for other oxidant/diluent combinations, including air plus diluent mixtures; however, no oxidant/diluent combination stronger than air should be used. Also, no unstable chemical capable of explosive decomposition reactions should be tested (see 8.3).
1.2 This test method is designed and written to be run at local ambient pressure and is limited to a maximum initial pressure of 1 atm abs. It may also be used for reduced pressures with the practical lower pressure limit being approximately 13.3 kPa (100 mm Hg). The maximum practical operating temperature of this equipment is approximately 150°C (302°F) (Note A1.2).
1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are provided for information only.
1.4 This standard should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions, and should not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.
1.5 This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety precautions are given in Section 8.
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Designation:E1232–91(Reapproved 1996)
Standard Test Method for
Temperature Limit of Flammability of Chemicals
This standard is issued under the fixed designation E 1232; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (ε) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The temperature limit of flammability test measures the minimum temperature at which liquid (or
solid) chemicals evolve sufficient vapors to form a flammable mixture with air under equilibrium
conditions. This temperature is applicable for assessing flammability in large process vessels and
similar equipment (Appendixes Appendix X1 and Appendix X2).
1. Scope 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers the determination of the mini-
responsibility of the user of this standard to establish appro-
mum temperature at which vapors in equilibrium with a liquid
priate safety and health practices and determine the applica-
(or solid) chemical will be sufficiently concentrated to form
bility of regulatory limitations prior to use. Specific safety
flammable mixtures in air at atmospheric pressure. This test
precautions are given in Section 8.
methodiswrittenspecificallyfordeterminationofthetempera-
ture limit of flammability of systems using air as the source of
2. Referenced Documents
oxidant and diluent. It may also be used for other oxidant/
2.1 ASTM Standards:
diluent combinations, including air plus diluent mixtures;
D 56 Test Method for Flash Point by Tag Closed Tester
however, no oxidant/diluent combination stronger than air
D 92 Test Method for Flash and Fire Points by Cleveland
should be used. Also, no unstable chemical capable of explo-
Open Cup
sive decomposition reactions should be tested (see 8.3).
D 93 Test Methods for Flash Point by Pensky-Martens
1.2 This test method is designed and written to be run at
Closed Cup Tester
local ambient pressure and is limited to a maximum initial
D 1310 Test Method for Flash Point and Fire Point of
pressureof1atmabs.Itmayalsobeusedforreducedpressures
Liquids by Tag Open-Cup Apparatus
with the practical lower pressure limit being approximately
D 3278 Test Method for Flash Point of Liquids by Small
13.3 kPa (100 mm Hg). The maximum practical operating
Scale Closed Cup Apparatus
temperature of this equipment is approximately 150°C (302°F)
D 3828 Test Method for Flash Point by Small Scale Closed
(Note A1.2).
Tester
1.3 The values stated in SI units are to be regarded as the
D 3934 Test Method for Flash/No Flash Test-Equilibrium
standard. The inch-pound units given in parentheses are
Method by a Closed-Cup Apparatus
provided for information only.
D 3941 Test Method for Flash Point by the Equilibrium
1.4 This standard should be used to measure and describe
Method With a Closed-Cup Apparatus
the properties of materials, products, or assemblies in response
E 220 Method for Calibration of Thermocouples by Com-
to heat and flame under controlled laboratory conditions, and
parison Techniques
shouldnotbeusedtodescribeorappraisethefirehazardorfire
E 230 Specification for Temperature-Electromotive Force
risk of materials, products, or assemblies under actual fire
(EMF) Tables for Standardized Thermocouples
conditions. However, results of this test may be used as
E 502 Test Method for Selection and Use of ASTM Stan-
elements of a fire risk assessment which takes into account all
dardsfortheDeterminationofFlashPointofChemicalsby
of the factors which are pertinent to an assessment of the fire
Closed Cup Methods
hazard of a particular end use.
Annual Book of ASTM Standards, Vol 05.01.
1 3
This test method is under the jurisdiction ofASTM Committee E-27 on Hazard Annual Book of ASTM Standards, Vol 06.01.
Potential of Chemicals and is the direct responsibility of Subcommittee E27.04 on Annual Book of ASTM Standards, Vol 05.02.
Flammability and Ignitability of Chemicals. Annual Book of ASTM Standards, Vol 14.03.
Current edition approved February 14, 1991. Published April 1991. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1232
formation for equilibrium situations in the chemical processing industry
E 537 Test Method for Assessing The Thermal Stability of
such as in closed process and storage vessels.
Chemicals By Methods of Differential Thermal Analysis
NOTE 2—Asaresultofflamequenchingeffectsexistingwhentestingin
E 681 Test Method for Concentration Limits of Flammabil-
standard closed-cup flashpoint apparatus, there are certain chemicals that
ity of Chemicals
exhibit no flashpoint but do evolve vapors that will propagate a flame in
E 698 Test Method for Arrhenius Kinetic Constants for
vessels of adequate size (X3.2).The temperature limit of flammability test
Thermally Unstable Materials
chamber is sufficiently large to overcome flame quenching effects in most
2.2 ANSI Standard: cases of practical importance, thus, usually indicating the presence of
vapor-phase flammability if it does exist (6.2).
ANSI-MC96.1 Temperature Measurement Thermocouples
NOTE 3—The lower temperature limit of flammability (LTL) is only
one of several characteristics that should be evaluated to determine the
3. Terminology
safety of a specific material for a specific application. For example, some
3.1 Definitions:
materialsarefoundtohaveanLTLbythistestmethodwhen,infact,other
3.1.1 flashpoint—the lowest temperature, corrected to a
characteristics such as minimum ignition energy and heat of combustion
pressure of 101.3 kPa (760 mm Hg, 1013 mbar), at which should also be considered in an overall flammability evaluation.
application of an ignition source causes the vapors of the
5.2 The vapor concentration present at the lower tempera-
specimen to ignite under specified conditions of test.
ture limit of flammability equals the lower flammable limit
3.1.2 lower limit of flammability or lower flammable limit,
concentration as measured by Test Method E 681 and extrapo-
(LFL)—the minimum concentration of a combustible sub-
lated back to the same temperature. (This permits estimation of
stance that is capable of propagating a flame through a
lower temperature limits of flammability if vapor pressure and
homogeneous mixture of the combustible and a gaseous
concentrationlimitofflammabilitydataareavailable(A2.3).A
oxidizer under the specified conditions of test.
comparison of results of the tests, thus, affords a check on test
3.1.3 lower temperature limit of flammability, (LTL)—the
reliability, the reliability of vapor pressure data, or both.)
lowest temperature, corrected to a pressure of 101.3 kPa (760
mm Hg, 1013 mbar), at which application of an ignition source
6. Interferences
causes a homogeneous mixture of a gaseous oxidizer and
6.1 This test method is not applicable to materials that
vaporsinequilibriumwithaliquid(orsolid)specimentoignite
undergo chemical changes when mixed with air. Examples
and propagate a flame away from the ignition source under the
include, but are not limited to, oxidation and polymerization.
specified conditions of test.
6.2 Measured temperature limits are influenced by flame
3.2 Definition of Term Specific to This Standard:
quenching effects of the test vessel walls. The test vessel
3.2.1 propagation of flame—theupwardandoutwardmove-
employed in this test method is of sufficient size to eliminate
ment of the flame front from the ignition source to the vessel
these effects for most materials. For certain amines, haloge-
walls, that is determined by visual observation.
nated materials, etc., that have large ignition-quenching dis-
tances, tests should be conducted in vessels with larger
4. Summary of Test Method
diameters than the one listed in this test method (A1.1).
4.1 A pool of liquid is stirred in a closed vessel in an air
Quenching effects become increasingly significant as the test
atmosphere.The vapor-air mixture above this liquid is exposed
pressure decreases.
to an ignition source and the upward and outward propagation
6.3 Measured temperature limits of flammability of chemi-
of flame away from the ignition source is noted by visual
cals can be greatly influenced, as are flashpoints, by the
observation. Temperature in the test vessel is varied between
presence of various impurities or known mixture components.
trials until the minimum temperature at which flame will
Small quantities of volatile flammable impurities can reduce
propagate away from the ignition source is determined.
temperature limit values, and volatile inert diluents can raise
temperature limit values or produce complete inerting. (See
5. Significance and Use
8.2.3 and Annex A3 for a discussion of mixture testing.)
5.1 The lower temperature limit of flammability is the
minimumtemperatureatwhichaliquid(orsolid)chemicalwill
7. Apparatus
evolve sufficient vapors to form a flammable mixture with air
7.1 Fig. 1 is a schematic diagram of the apparatus; details
under equilibrium conditions. Knowledge of this temperature
and dimensions are presented in Annex A1. The apparatus
is important in determining guidelines for the safe handling of
consists of the following:
chemicals, particularly in closed process and storage vessels.
7.1.1 Glass Test Vessel,
NOTE 1—As a result of physical factors inherent in flashpoint apparatus 7.1.2 Insulated Chamber, equipped with a source of
and procedures, closed-cup flashpoint temperatures are not necessarily the
controlled-temperature air,
minimum temperature at which a chemical will evolve flammable vapors
7.1.3 Ignition Device, with an appropriate power supply,
(see Appendix X2 and Appendix X3, taken in part from Test Method
and
E 502). The temperature limit of flammability test is designed to supple-
7.1.4 Magnetic Stirrer and Cover, equipped with the neces-
ment limitations inherent in flashpoint tests (Appendix X2). It yields a
sary operating connections and components.
result closely approaching the minimum temperature of flammable vapor
8. Hazards
8.1 Tests should not be conducted in this apparatus with
Available from American National Standards Institute, 1430 Broadway, New
York, NY 10018. gaseous oxidants stronger than air since explosive violence
E1232
FIG. 1 Schematic Diagram of Test Apparatus
increases as oxidizer strength increases. Do not use oxygen, specifictemperature.Ifcorrosionoccurs,materialsofconstruc-
nitrous oxide, nitrogen dioxide, chlorine, etc. in this glass tion should be changed to corrosion resistant types.
apparatus. 8.2.4 Testingshouldbecarriedoutinamannerthatprevents
8.2 Adequate shielding must be provided to prevent injury accidental activation of the ignition source at incorrect stages
in the event of equipment rupture, due to both implosions and of the procedure.
explosions. A metal enclosure such as that recommended in 8.3 Tests should not be conducted on peroxides, monopro-
A1.2 is one method suitable for this purpose. pellants, or other thermally unstable materials that might
8.2.1 Implosion of the test vessel at high vacuum levels is undergoexplosivegasorliquidphasedecompositionreactions.
possible and, therefore, all evacuations must be made with the For example, some monomers may undergo energetic vapor
required shielding to protect against flying fragments. phase polymerization reactions. For information on evaluating
8.2.2 Energetic explosions may be produced if tests are the thermal stability of proposed test materials, see DS-51A,
made at temperatures above the LTL. The determination of the and Test Methods E 537 and E 698.
LTL should always be initiated at a temperature below the 8.4 Tests should be conducted in a fume hood or other
estimated LTL, and successive ignition trials made at intervals ventilated area to prevent exposure of personnel to toxic
of not more than a 2°C temperature increase. Methods for chemicals or combustion products.
estimating initial test temperatures, discussed in Annex A2, 8.5 Precautions must be taken to ensure that the high
shouldbeemployedtoensurethatinitialtrialsareconductedat voltage spark ignition source is always adequately insulated
temperatures less than the LTL (Note 4). The glass test vessel, from other electrical circuits and metal parts of the apparatus,
equipped with a lightly held or loose cover, vents most fume hood, etc. to prevent electrical hazards to personnel and
explosions adequately. Nevertheless, shielding is required to instrumentation. Careful attention to electrical insulation integ-
protect against any possibility of test vessel rupture. rity plus the use of disconnection procedures are required to
8.2.3 The testing of materials that are reactive with the achieve a satisfactory protection against electrical hazards.
metal parts of the apparatus can effect results, and may cause
9. Calibration
energetic explosions. For example, acids and alkaline materials
can generate hydrogen gas. When testing such materials, 9.1 System temperature and pressure and barometric pres-
variable results due to the generation of hydrogen may be sure measuring devices must be calibrated against adequate
detected by varying the holding time of several trials at a standards.Forinformationoncalibrationofthermocouples,see
E1232
NOTE 7—Although this test method is intended to be applied to vapor
Method E 220, Specification E 230, and ANSI-MC96.1. The
situations only, it is theoretically possible to generate mist in some
pressure sensing devices should be calibrated against a trace-
situations.Anymisttendstogiveamoreconservative(lower)temperature
able standard such as a primary standard piston gage, com-
limit.
monly called a dead weight gage.
10.2.9 Darken the viewing area. Activate the ignition
10. Procedures
source. Observe for ignition and flame propagation away from
10.1 Lower Temperature Limit of Flammability Test—
the ignition source. At each test temperature record any
10.1.1 Assemble the equipment, as shown in Fig. 1, within
occurrence of flame propagation.
an appropriate fume hood or other ventilated area and secure
the door of the metal enclosure. Clean and dry the test vessel
NOTE 8—It is recommended that the ignition source not be activated
and all components. Evacuate the system and flush with air, or
until 30 s after the stirrer is turned off to allow the mixture to become
other specified test gas, sufficiently to ensure removal of quiescent. However, to prevent stratification activate the ignition source
within 60 s.
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