ASTM E2021-09(2013)
(Test Method)Standard Test Method for Hot-Surface Ignition Temperature of Dust Layers
Standard Test Method for Hot-Surface Ignition Temperature of Dust Layers
SIGNIFICANCE AND USE
5.1 This test method is applicable to dusts and powders, and provides a procedure for performing laboratory tests to evaluate hot-surface ignition temperatures of dust layers.
5.2 The test data can be of value in determining safe operating conditions in industrial plants, mines, manufacturing processes, and locations of material usage and storage.
5.3 Due to variation of ignition temperature with layer thickness, the test data at one thickness may not be applicable to all industrial situations (see Appendix X1). Tests at various layer thicknesses may provide a means for extrapolation to thicker layers, as listed in the following for pulverized Pittsburgh bituminous coal dust (2). Mathematical modeling of layer ignition at various layer thicknesses is described in Ref. (3).
Layer Thickness, mm
Hot-Surface Ignition Temperature, °C
6.4
300
9.4
260
12.7
240
25.4
210
5.4 This hot plate test method allows for loss of heat from the top surface of the dust layer, and therefore generally gives a higher ignition temperature for a material than Test Method E771, which is a more adiabatic system.
5.5 This test method for dust layers generally will give a lower ignition temperature than Test Method E1491, which is for dust clouds. The layer ignition temperature is determined while monitoring for periods of minutes to hours, while the dust cloud is only exposed to the furnace for a period of seconds.Note 1—Much of the literature data for layer ignition is actually from a basket in a heated furnace (4), known as the modified Godbert-Greenwald furnace test. Other data are from nonstandardized hot plates (5-9).
5.6 Additional information on the significance and use of this test method may be found in Ref. (10).
SCOPE
1.1 This test method covers a laboratory procedure to determine the hot-surface ignition temperature of dust layers, that is, measuring the minimum temperature at which a dust layer will self-heat. The test consists of a dust layer heated on a hot plate.2,3
1.2 Data obtained from this test method provide a relative measure of the hot-surface ignition temperature of a dust layer.
1.3 This test method should be used to measure and describe the properties of materials in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire hazard risk of materials, products, or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment that takes into account all of the factors that are pertinent to an assessment of the fire hazard risk of a particular end use product.
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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2021 − 09(Reapproved 2013)
Standard Test Method for
Hot-Surface Ignition Temperature of Dust Layers
This standard is issued under the fixed designation E2021; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope E771 Test Method for Spontaneous Heating Tendency of
Materials (Withdrawn 2001)
1.1 This test method covers a laboratory procedure to
E1445 Terminology Relating to Hazard Potential of Chemi-
determine the hot-surface ignition temperature of dust layers,
cals
that is, measuring the minimum temperature at which a dust
E1491 Test Method for MinimumAutoignition Temperature
layer will self-heat. The test consists of a dust layer heated on
2,3 of Dust Clouds
a hot plate.
2.2 IEC Standard:
1.2 Data obtained from this test method provide a relative
IEC 1241-2-1 Electrical Apparatus for Use in the Presence
measure of the hot-surface ignition temperature of a dust layer.
of Combustible Dust; Part 2: Test Methods—Section 1:
1.3 Thistestmethodshouldbeusedtomeasureanddescribe
MethodsforDeterminingtheMinimumIgnitionTempera-
the properties of materials in response to heat and flame under
tures of Dusts, Method A
controlled laboratory conditions and should not be used to
describe or appraise the fire hazard or fire hazard risk of
3. Terminology
materials, products, or assemblies under actual fire conditions.
3.1 Definitions—For definitions of other terms used in this
However, results of this test method may be used as elements
standard, see Terminology E1445.
ofafireriskassessmentthattakesintoaccountallofthefactors
3.2 Definitions of Terms Specific to This Standard:
that are pertinent to an assessment of the fire hazard risk of a
3.2.1 hot-surface ignition temperature of a dust layer,
particular end use product.
n—lowest set temperature of the hot plate that causes ignition
1.4 The values stated in SI units are to be regarded as
of the dust layer.
standard. No other units of measurement are included in this
3.2.2 ignition of a dust layer, n—initiation of self-heating or
standard.
combustion in a material under test.
1.5 This standard does not purport to address all of the
3.2.3 ignition time, n—time between the start of heating and
safety concerns, if any, associated with its use. It is the
the point at which the maximum temperature or flaming
responsibility of the user of this standard to establish appro-
combustion is reached.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. Specific precau- 3.2.4 temperature rise, ∆T, n—the difference between T
max
tionary statements are given in Section 8. and the initial set temperature of the hot plate.
3.2.5 T ,n—maximum temperature measured during test.
max
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 The test material is placed within a metal ring on top of
a hot plate, that is at a preset constant temperature.
This test method is under the jurisdiction ofASTM Committee E27 on Hazard
4.2 The sample temperature is monitored to determine
Potential of Chemicals and is the direct responsibility of Subcommittee E27.04 on
temperature rise due to oxidative reactions or decomposition
the Flammability and Ignitability of Chemicals.
Current edition approved Oct. 1, 2013. Published October 2013. Originally
reactions, or both.
approved in 1999. Last previous edition approved in 2009 as E2021 – 09. DOI:
4.3 Ignitionisconsideredtohavetakenplacewheneitherof
10.1520/E2021-09R13.
This test method is based on recommendations of the National Materials
the following occurs:
Advisory Board of the National Academy of Sciences (1).
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
4 5
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2021 − 09 (2013)
4.3.1 Temperature in the dust layer at position of thermo- 5.6 Additional information on the significance and use of
couple rises at least 50°C above the hot plate temperature, or this test method may be found in Ref. (10).
4.3.2 Visible evidence of combustion is apparent, such as
red glow or flame. 6. Limitations and Interferences
4.4 Hot plate surface temperature is varied from test to test,
6.1 This test method should not be used with materials
as necessary, until the hot-surface ignition temperature is
having explosive or highly reactive properties.
determined.
6.2 Ifthemetal(forexample,aluminum)plateorringreacts
with the test material, choose another type of metal that does
5. Significance and Use
not react.
5.1 This test method is applicable to dusts and powders, and
provides a procedure for performing laboratory tests to evalu-
7. Apparatus
ate hot-surface ignition temperatures of dust layers.
7.1 The complete apparatus, shown in Fig. 1, consists of a
5.2 The test data can be of value in determining safe
circular metal (for example, aluminum) plate centrally posi-
operating conditions in industrial plants, mines, manufacturing
tioned on top of a hot plate. The dust layer is confined within
processes, and locations of material usage and storage.
a metal ring on top of the metal plate. An example of an
5.3 Due to variation of ignition temperature with layer
apparatus that has been found suitable is given in Appendix
thickness, the test data at one thickness may not be applicable
X2.
to all industrial situations (see Appendix X1). Tests at various
7.1.1 Heated Surface,consistingofametalplateofapproxi-
layer thicknesses may provide a means for extrapolation to
mately 200-mm diameter and at least 20-mm thick. This plate
thicker layers, as listed in the following for pulverized Pitts-
is centrally placed on top of a commercial hotplate.Athermo-
burgh bituminous coal dust (2). Mathematical modeling of
couple is mounted radially in the metal plate, with its junction
layer ignition at various layer thicknesses is described in Ref.
in contact with the plate within 1.0 6 0.5 mm of the upper
(3).
surface. This thermocouple is connected to a temperature
Layer Thickness, mm Hot-Surface Ignition Temperature, °C controller. The plate and its thermocouple-controller assembly,
6.4 300
in conjunction with the commercial hotplate, should satisfy the
9.4 260
following requirements:
12.7 240
25.4 210
7.1.1.1 The plate should be capable of attaining a maximum
temperature of 400°C without a dust layer in position,
5.4 This hot plate test method allows for loss of heat from
the top surface of the dust layer, and therefore generally gives 7.1.1.2 Thetemperaturecontrollermustbecapableofmain-
a higher ignition temperature for a material than Test Method taining the temperature of the plate constant to within 65°C
E771, which is a more adiabatic system. throughout the time period of the test,
7.1.1.3 When the temperature of the plate has reached a
5.5 This test method for dust layers generally will give a
constant value, the temperature across the plate should be
lower ignition temperature than Test Method E1491, which is
uniform to within 65°C, as shown in Fig. 2,
for dust clouds. The layer ignition temperature is determined
7.1.1.4 The temperature control should be such that the
while monitoring for periods of minutes to hours, while the
recorded plate temperature will not change by more than 65°
dust cloud is only exposed to the furnace for a period of
C during the placing of the dust layer and will be restored to
seconds.
within 2°C of the previous value within 5 min of placing the
NOTE 1—Much of the literature data for layer ignition is actually from
dust layer, and
a basket in a heated furnace (4), known as the modified Godbert-
7.1.1.5 The thermocouple in the plate and its readout device
Greenwald furnace test. Other data are from nonstandardized hot plates
(5-9). should be calibrated and should be accurate to within 63°C.
FIG. 1 Schematic of Hotplate Layer Ignition Apparatus
E2021 − 09 (2013)
8.5 Tests should be conducted in a ventilated hood or other
area having adequate ventilation to remove any smoke or
fumes.
9. Sampling and Test Specimens
9.1 It is not practical to specify a single method of sampling
dust for test purposes because the character of the material and
its available form affect selection of the sampling procedure.
Generally accepted sampling procedures should be used. See
MNL 32 Manual on Test Sieving Methods.
9.2 Tests may be run on an as-received sample. However,
since finer dusts have lower hot-surface ignition temperatures
(2) and due to the possible accumulation of fines at some
locations in a processing system, it is recommended that the
test sample be at least 95 % minus 200 mesh (75 µm). To
achieve this particle fineness, grind, pulverize, or sieve the
sample.
NOTE 2—The operator should consider the thermal stability and the
friction and impact sensitivity of the dust during any grinding or
FIG. 2 Uniformity of Aluminum Plate Temperature at Set Tempera-
pulverizing. In sieving the material, the operator must verify that there is
ture of 250°C
no selective separation of components in a dust that is not a pure
substance.
NOTE 3—It may be desirable in some cases to conduct dust layer
ignition tests on a material as sampled from a process because (a) dust
7.1.2 Metal Ring, to be placed on the heated metal plate, for
streams may contain a wide range of particle sizes or have a well-defined
containing the dust layer. Stainless steel is suitable for most
specific moisture content, (b) materials consisting of a mixture of
dusts. The standard ring is 12.7 mm ( ⁄2 in.) in depth and chemicals may be selectively separated on sieves, and (c) certain fibrous
materialsmaynotpassthrougharelativelycoarsescreen.Whenamaterial
approximately 100 mm (4 in.) in diameter. Rings may be of
is tested in the as-received state, it should be recognized that the test
other depths.
results may not represent the lowest dust layer ignition temperature
7.1.3 Dust Layer Thermocouple—Slots on opposite sides of
possible. Any process change resulting in a higher fraction of fines than
theperimeteroftheringaccommodatethepositioningofatype
normal or drier product than normal may decrease the ignition tempera-
ture.
K bare thermocouple (0.20 to 0.25 mm or 10 mil in diameter)
through the dust sample. This bare thermocouple is positioned
10. Calibration and Standardization
parallel to the surface of the metal plate with its junction at the
10.1 The calibration of the dust sample thermocouple and
geometric center of the dust layer. This thermocouple should
be connected to a digital thermometer for observing the the thermocouple embedded in the circular metal plate must be
checked using appropriate standards.
temperature of a dust layer during a test. Temperature mea-
surements with the thermocouple should be made either
10.2 The temperature across the metal plate should be
relative to a fixed reference junction temperature or with
uniform to within 65°C when measured across two diameters
automatic cold junction compensation. Most digital thermom-
at right angles, as shown in Fig. 2. This requirement must be
eters have built-in compensation.The thermocouple in the dust
satisfied at two plate temperatures, one in the range of between
layer and its readout device should be calibrated and should be
200 and 250°C and the second in the range of between 300 and
accurate to within 63°C.
350°C, measured at the center of the plate.
7.2 Ambient Temperature Thermometer, placed in a conve-
10.3 Verify the performance of the apparatus using at least
nientpositionwithin1mofthehotplatebutshieldedfromheat
two dust layers having different hot-surface ignition tempera-
convection and radiation from the hot plate. The ambient
tures. Representative data including both publishedandunpub-
temperature should be within the range of 15 to 30°C.
lished values (2) for 12.7-mm thick layers of three dusts are:
Brass 155-160°C
8. Hazards
Pittsburgh coal dust 230-240°C
Lycopodium spores 240-250°C
8.1 The user should consider the toxicity of the sample dust
The brass was a very fine flake (100 % minus 325 mesh)
and possible combustion products.
with a small amount (<1.7 %) of stearic acid coating. The
8.2 This test method should not be used with materials
lycopodium is a natural plant spore having a narrow size
having explosive or highly reactive properties.
distribution with 100 % minus 200 mesh and mass median
8.3 Metal dusts can ignite and burn with high temperatures.
diameter of ;28 µm. This is the reticulate form Lycopodium
If a flame is observed, the dust layer should be covered with a
clavatum. The Pittsburgh seam bituminous coal has ;80 %
flat metal sheet to exclude the air and extinguish the flame.
8.4 The user should use due caution around the hot surfaces
Some data are from unpublished work of the Fenwal (Marlborough, MA) and
present on the test apparatus. Fike (Blue Springs, MO) companies.
E2021 − 09 (2013)
minus 200 mesh, a mass median diameter of ;45 µm, and any self-heating is evident. Self-heating may be indicated by
36 % volatility.Additional data that can be used for calibration localized heavy smoke, or increasing temperature. Terminate
arethoselistedin5.3fordifferentlayerthicknessesof this coal
the test if the layer has completely melted, ignited, or reached
dust. a maximum temperature without igniting and is cooling down.
NOTE 5—Ignition in particulate or fine dusts exposed to elevated
11. Procedure
temperatures generally is preceded by a more or less protracted period of
11.1 GeneralSet-Up—Setuptheapparatusinapositionfree
self-heating, usually due to atmospheric oxidation. Depending on the
from drafts while exhausting smoke and fumes. Ensure that the temperature of exposure, self-heating may result in no more than a
transient, although sometimes substantial, rise in temperature within the
air flow in the hood is sufficient for removing smoke and
material that does not lead to the propagation of combustion. It is
fumes, but low enough so as not to disturb t
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.