ASTM E2019-03(2013)
(Test Method)Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air
Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air
SIGNIFICANCE AND USE
5.1 This test method provides a procedure for performing laboratory tests to determine the minimum ignition energy of a dust cloud.Note 1—For gases and vapors, see Test Method E582.
5.2 The data developed by this test method may be used to assess the spark ignitibility of a dust cloud. Additional guidance on the significance of minimum ignition energy is in X1.1.
5.3 The values obtained are specific to the sample tested, the method used and the test equipment used. The values are not to be considered intrinsic material constants.
5.4 The MIE of a dust as determined using this procedure can be compared with the MIE's of reference dusts (using the same procedure) to obtain the relative sensitivity of the dust to spark ignition. An understanding of the relative sensitivity to spark ignition can be used to minimize the probability of explosions due to spark ignition.
SCOPE
1.1 This test method determines the minimum ignition energy of a dust cloud in air by a high voltage spark.
1.2 The Minimum Ignition Energy (MIE) of a dust-cloud is primarily used to assess the likelihood of ignition during processing and handling. The likelihood of ignition is used to evaluate the need for precautions such as explosion prevention systems. The MIE is determined as the electrical energy stored in a capacitor which, when released as a high voltage spark, is just sufficient to ignite the dust cloud at its most easily ignitable concentration in air. The laboratory test method described in this standard does not optimize all test variables that affect MIE. Smaller MIE values might be determined by increasing the number of repetitions or optimizing the spark discharge circuit for each dust tested.
1.3 In this test method, the test equipment is calibrated using a series of reference dusts whose MIE values lie within established limits. Once the test equipment is calibrated, the relative ignition sensitivity of other dusts can be found by comparing their MIE values with those of the reference dusts or with dusts whose ignition sensitivities are known from experience. X1.1 of this test method includes guidance on the significance of minimum ignition energy with respect to electrostatic discharges.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, 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 precautionary statements are given in Section 8.
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Designation: E2019 − 03 (Reapproved 2013)
Standard Test Method for
Minimum Ignition Energy of a Dust Cloud in Air
This standard is issued under the fixed designation E2019; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method determines the minimum ignition
D3173Test Method for Moisture in theAnalysis Sample of
energy of a dust cloud in air by a high voltage spark.
Coal and Coke
1.2 The Minimum Ignition Energy (MIE) of a dust-cloud is
D3175Test Method for Volatile Matter in the Analysis
primarily used to assess the likelihood of ignition during
Sample of Coal and Coke
processing and handling. The likelihood of ignition is used to
E582 Test Method for Minimum Ignition Energy and
evaluate the need for precautions such as explosion prevention Quenching Distance in Gaseous Mixtures
systems.The MIE is determined as the electrical energy stored E789Test Method for Dust Explosions in a 1.2-Litre Closed
Cylindrical Vessel (Withdrawn 2007)
in a capacitor which, when released as a high voltage spark, is
E1226Test Method for Explosibility of Dust Clouds
justsufficienttoignitethedustcloudatitsmosteasilyignitable
E1445Terminology Relating to Hazard Potential of Chemi-
concentration in air. The laboratory test method described in
cals
this standard does not optimize all test variables that affect
2.2 IEC Standards:
MIE. Smaller MIE values might be determined by increasing
1241-2-3, 1994ElectricalApparatus for Use in the Presence
the number of repetitions or optimizing the spark discharge
of Combustible Dusts, Part 2: Test Method, Section 3:
circuit for each dust tested.
Method for Determining Minimum Ignition Energy of
1.3 Inthistestmethod,thetestequipmentiscalibratedusing
Dust-Air Mixtures
a series of reference dusts whose MIE values lie within
3. Terminology
established limits. Once the test equipment is calibrated, the
relative ignition sensitivity of other dusts can be found by
3.1 Definitions—For additional definitions, see Terminol-
comparing their MIE values with those of the reference dusts
ogy E1445.
or with dusts whose ignition sensitivities are known from
3.2 Definitions of Terms Specific to This Standard:
experience. X1.1 of this test method includes guidance on the 3.2.1 spark discharge, n—transient discrete electric
significance of minimum ignition energy with respect to discharge, which takes place between two conductors, which
are at different potentials. The discharge bridges the gap
electrostatic discharges.
between the conductors in the form of a single ionization
1.4 The values stated in SI units are to be regarded as
channel.
standard. No other units of measurement are included in this
3.2.2 minimum ignition energy (MIE), n—electrical energy
standard.
discharged from a capacitor, which is just sufficient to effect
1.5 This standard does not purport to address all of the ignition of the most easily ignitable concentration of fuel in air
safety concerns, if any, associated with its use. It is the
under the specific test conditions.
responsibility of the user of this standard to establish appro-
3.2.3 ignition delay time, n—the time between the onset of
priate safety and health practices and determine the applica-
dispersion of the dust sample into a cloud and the activation of
bility of regulatory limitations prior to use. Specific precau-
the ignition source.
tionary statements are given in Section 8.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This test method is under the jurisdiction ofASTM Committee E27 on Hazard Standards volume information, refer to the standard’s Document Summary page on
Potential of Chemicalsand is the direct responsibility of Subcommittee E27.05 on the ASTM website.
Explosibility and Ignitability of Dust Clouds. The last approved version of this historical standard is referenced on
Current edition approved Oct. 1, 2013. Published November 2013. Originally www.astm.org.
approved in 1999. Last previous edition approved in 2007 as E2019–03 (2007). Available from International Electrotechnical Commission (IEC), 3 rue de
DOI: 10.1520/E2019-03R13. Varembé, Case postale 131, CH-1211, Geneva 20, Switzerland, http://www.iec.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2019 − 03 (2013)
4. Summary of Test Method other suitable chambers can be used provided that the calibra-
tion requirements in 10.1 are met.
4.1 A dust cloud is formed in a laboratory chamber by an
introduction of the material with air.
7.2 Spark Generation Circuit—The Appendix describes
some suitable forms of circuits, all of which shall have the
4.2 Ignition trials of this dust-air mixture are then
following characteristics:
attempted, after a specific ignition delay time, by a spark
7.2.1 Electrode Material, such as tungsten, stainless steel,
discharge from a charged capacitor.
brass, or graphite.
4.3 The stored energy discharged into the spark and the
7.2.2 Electrode Diameter and Shape, 2 6 1 mm. For
occurrence or nonoccurrence of flame are recorded.
circuits in which high voltage is maintained across the spark
4.4 The minimum ignition energy is sought by varying the
gap prior to spark breakdown, a significant fraction of the
dust concentration, the spark discharge energy and optionally
energy stored in the capacitor may drain away as corona
the ignition delay time.
discharges from sharp electrode tips prior to the spark dis-
charge. This is increasingly important at low stored energies.
4.5 Ignition is determined by visual observation of a flame
Electrodes with rounded tips can be used to reduce corona
propagation away from the spark gap.
effects that can occur with pointed electrodes, which may give
5. Significance and Use incorrectvaluesofsparkenergy.Ifpointedelectrodesareused,
corona effects should be considered carefully.
5.1 This test method provides a procedure for performing
7.2.3 Electrode Gap—The optimum spacing is typically of
laboratory tests to determine the minimum ignition energy of a
the order of 6 mm. For certain materials at low ignition energy
dust cloud.
values, however, the gap spacing may need to be reduced in
NOTE 1—For gases and vapors, see Test Method E582.
ordertoinitiatethespark.Underthesecircumstances,thespark
5.2 The data developed by this test method may be used to
gapcanbereducedandthetestscarriedoutwiththelargestgap
assess the spark ignitibility of a dust cloud. Additional guid-
possible, but the gap should not be less than 2 mm.
ance on the significance of minimum ignition energy is in
NOTE 2—The capacitance of the electrodes and associated high voltage
X1.1.
cables between the storage capacitor and the electrodes should be as low
as possible. It should be noted that cable capacitance may be of the order
5.3 Thevaluesobtainedarespecifictothesampletested,the
40pF/m depending on its construction, which represents significant
methodusedandthetestequipmentused.Thevaluesarenotto
additional stored energy at low storage capacitance and high voltage. The
be considered intrinsic material constants.
stray capacitance of these components must be measured to determine if
it needs to be taken into account when calculating the stored circuit
5.4 The MIE of a dust as determined using this procedure
energy.
can be compared with the MIE’s of reference dusts (using the
NOTE3—Insulationresistancebetweenelectrodesshouldbesufficiently
same procedure) to obtain the relative sensitivity of the dust to
high to prevent leakage currents prior to discharge. Typically, a minimum
spark ignition. An understanding of the relative sensitivity to 12
resistance between the electrodes of 10 Ω is required for a minimum
spark ignition can be used to minimize the probability of
ignitionenergyof1mJ,and10 Ωforaminimumignitionenergyof100
mJ. Insulation resistance may decrease over time due to contamination of
explosions due to spark ignition.
thesurfacewithcarbonandothermaterials.Theresistancemaybedirectly
measured across the electrodes.Alternatively, a decrease may be inferred
6. Interferences
by the inability to hold constant voltage on the isolated storage capacitor
6.1 Dust residue from previous tests may affect results. The for the timescale of a test.
chamber must be cleaned before a new product is tested. NOTE 4—Almost all electrostatic discharges in plant installations are
capacitive with negligible inductance. It has been found that for equal
6.2 Problems may arise due to electrical shortcircuits when
stored energies many dusts can be ignited more easily when a resistor or
using conductive materials.
an inductance is placed in the discharge circuit to create longer duration
sparks. Ideally, the MIE should correspond to circuits whose discharge
duration has been optimized for the dust in question using, for example,
7. Apparatus
an inductance.
7.1 Test Apparatus—Although a number of different test
apparatuses are used in practice, they all have the following
8. Safety Precautions
components in common:Atest chamber, spark electrodes, and
8.1 Prior to handling a test material, the toxicity of the
a spark generation circuit. Various configurations of the spark
sample and its combustion products must be considered. This
generation circuits are provided in the Appendix X1. The
information is generally obtained from the manufacturer or
purpose of the test chamber is to produce a uniform, nontur-
supplier. Appropriate safety precautions must be taken if the
bulent and known density dust cloud in air at the time of
materialhastoxicorirritatingcharacteristics.MIE-testsshould
ignition.TheclearplasticorglassHartmanntube,typically0.5
be conducted in a ventilated hood or other area having
or 1.2 L, and the 20-L sphere apparatus have been found
adequate ventilation.
suitable for this test method. These vessels are described in
Refs (1-4) and Test Methods E789 and E1226. These and
8.2 Before initiating a test, check and secure the apparatus,
fittings and gaskets to prevent leakage.
8.3 All enclosures containing electrical equipment must be
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. connected to a common ground.
E2019 − 03 (2013)
8.4 The test method should not be used with recognized
explosives, such as gunpowder or dynamite; pyrophoric sub-
stances; or, substances or mixtures of substances, which may
under some circumstances behave in a similar manner without
considering the special hazards. Where any doubt exists about
the existence of a hazard due to explosive properties, expert
advice should be sought.
8.5 Because the apparatus consists of a circuit with high
voltagecomponents,adequatesafeguardsmustbeemployedto
prevent electrical shock to personnel.
8.6 The operator should work from a protected location,
such as from outside a closed fume hood, in case of vessel or
electrical failure.
8.7 Care should be taken not to clean acrylic Hartmann
FIG. 2 Influence of the Humidity (Water Content) of Combustible
Dusts (5)
tubes with incompatible solvents, which can lead to embrittle-
ment and cracking.
9.3 To achieve this particle fineness (≥95% minus 200
9. Sampling
mesh) the sample may be ground or pulverized, or it may be
9.1 Itisnotpracticaltospecifyasinglemethodofsampling sieved.
dust for test purposes because the character of the material and
NOTE 5—The operator should consider the thermal stability of the dust
its available form affect selection of the sampling procedure.
during grinding or pulverizing.
NOTE6—Insomecases,itmaybedesirabletoconductdustdeflagration
9.2 Minimum ignition energy decreases with decreasing
tests on material as sampled from a process because process dust streams
particle size (see Fig. 1). Although tests may be run on an
may contain a wide range of particle sizes or have a well-defined specific
“as-received” sample, explosible dust clouds often consist
moisture content. When a material is tested in the as-received state, it
largelyofsub-200meshdust,whichaccumulatesinsuspension should be recognized that the test results may not represent the most
severe ignition hazards possible.Any process change resulting in a higher
when coarser bulk powder is handled. Therefore, it is recom-
fraction of fines or drier product may result in a lower MIE for the
mended that the test sample be at least 95% minus 200 mesh
product.
(75µm).Ingeneral,thesampletestedshouldbeatleastasfine
NOTE 7—The possible reduction of the particle size due to attrition by
as the dust at the location being considered, which, in some
the dust dispersion system of the test apparatus should be considered.
cases, may require testing of sub-325 mesh or even finer dust. NOTE 8—In sieving the material, the operator must verify that there is
no selective separation of components in a dust that is not a pure
substance. Materials consisting of a mixture of chemicals may be
separated selectively on sieves and certain fibrous materials, which may
not pass through a relatively coarse screen may produce dust deflagra-
tions.
9.4 Minimum ignition energy for some dusts increases with
increased moisture content (see Fig. 2). Dusts should be tested
either in the dry state or approximating the moisture content
under the handling conditions of interest. “Dry” samples
shouldbetransportedtothetestlaboratoryinsealedcontainers
under dry air or nitrogen, and then stored in a desiccator.
Desiccants, such as phosphorus pentoxide, may be more
effective than silica gel in removing residual moisture.
NOTE 9—There is no single method for determining the moisture
content or for drying a sample. Sample drying equally is complex due to
the presence of volatiles, lack of or varying porosity (see Test Methods
D3173 and D3175), and sensitivity of the sample to heat; therefore, each
must be dried in a manner that will not modify or destroy the integrity of
the sample. Hygroscopic materials must be desiccated.
10. Calibration and Standardization
10.1 Calibration tests should be carried out on at least three
different reference dusts. The results shall be within the
FIG. 1 Correlation of Median Particle Size and MIE (5) following ranges (measured without inductance):
E2019 − 03 (2013)
being tested. Then, the spark energy is reduced in steps, for
Irganox 1010: MIE=1to6mJ
Anthraquinone: MIE=1to11mJ
example,factorof ;3,atthegiven
...
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