ASTM E789-95
(Test Method)Standard Test Method for Dust Explosions in a 1.2-Litre Closed Cylindrical Vessel
Standard Test Method for Dust Explosions in a 1.2-Litre Closed Cylindrical Vessel
SCOPE
1.1 This test method covers the determination of the ignition of a dust dispersed in air, within a closed vessel.
1.2 This test method provides a measure of dust explosion pressure and rate of pressure rise. It does not provide a definitive determination of the flammability of a dust and has other severe limitations which are identified in Section 5. The preferred method for the design of safety equipment is Test Method E1226.
1.3 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. For specific safety precautions see Section 7.
1.4 The values stated in inch-pound units are to be regarded as the standard. The values in parentheses are for information only.
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Designation: E 789 – 95
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Dust Explosions in a 1.2-Litre Closed Cylindrical Vessel
This standard is issued under the fixed designation E 789; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
1.1 This test method covers the determination of the ignition 4.1 This test method provides a procedure for measuring
of a dust dispersed in air, within a closed vessel. pressure and rate of pressure rise.
1.2 This test method provides a measure of dust explosion 4.2 This test method may be used to determine whether a
pressure and rate of pressure rise. It does not provide a dust will ignite using an electric arc ignition source.
definitive determination of the flammability of a dust and has
5. Limitation
other severe limitations which are identified in Section 5. The
preferred method for the design of safety equipment is Test 5.1 The values determined by this test method are specific to
the material tested and equipment and procedure used and are
Method E 1226.
1.3 This standard does not purport to address all of the not to be considered inherent, fundamental properties.
5.2 The size and shape of the vessel have a direct bearing on
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- the data obtained. Extrapolation to vessels having a different
volume and shape should not be made.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific safety 5.3 The data cannot be used for direct calculation of
explosion venting or containment.
precautions see Section 7.
1.4 The values stated in inch-pound units are to be regarded 5.4 A dust cloud that does not ignite by this test method may
still be flammable. This test method does not provide a
as the standard. The values in parentheses are for information
only. definitive determination of the flammability of a dust.
6. Apparatus
2. Referenced Documents
2.1 ASTM Standards: 6.1 The equipment consists of a verticall mounted closed
steel combustion chamber (commonly known as the Hartmann
D 3173 Test Method for Moisture in the Analysis Sample of
Coal and Coke tube), a dust dispersion system using clean air, ignition source,
pressure sensor, and recording system.
D 3175 Test Method for Volatile Matter in the Analysis
Sample of Coal and Coke 6.2 Fig. 1 is a schematic diagram of the apparatus.
6.3 Construction details and tables are presented in the
E 1226 Test Method for Pressure and Rate of Pressure Rise
for Combustible Dusts annexes.
2.2 Other ASTM Document: 6.4 The pressure transducer should be installed and operated
according to the manufacturer’s recommendations.
STP 447A Manual on Test Sieving Methods
3. Summary of Test Method 7. Safety Precautions
7.1 Prior to handling a dust material, the toxicity of the
3.1 A dust cloud is formed in a closed steel combustion
chamber by a jet of clean compressed air and ignited by a sample and its combustion products must be considered; this
information is generally obtained from the manufacturer or
continuous electric arc.
3.2 The pressure is detected by a transducer and recorded by supplier. Appropriate safety precautions must be taken if the
material has toxic or irritating characteristics. Tests using this
appropriate measuring equipment from which pressure and rate
of pressure rise may be determined. apparatus must be in a ventilated hood or other area having
adequate ventilation.
7.2 Before initiating a test check and secure the Hartmann
This test method is under the jurisdiction of ASTM Committee E-27 on Hazard
apparatus, fittings, and gaskets to prevent leakage.
Potential of Chemicals and is the direct responsibility of Subcommittee E27.05 on
7.3 All testing should start using 0.1 g of sample to prevent
Dusts.
over-pressurization due to high-energy materials. No experi-
Current edition approved Nov. 10, 1995. Published January 1996. Originally
published as E 789 – 81. Last previous edition E 789 – 89.
emtns should be run so that the explosion pressure exceeds 175
Annual Book of ASTM Standards, Vol 05.05
psig (1.21 MPa).
Annual Book of ASTM Standards, Vol 14.02.
7.4 In assembling the electricl circuitry for this apparatus,
E 789
NOTE 1—Cam switch timer operates solenoid valve, spark ignition, and recording oscillograph.
FIG. 1 Schematic of Apparatus for Determining Pressure and Rate of Pressure in a Dust Explosion
during any grinding or pulverizing. In sieving the material, the operator
standard wiring and grounding procedures must be followed.
must verify that there is no selective separation of components in a dust
Since the high-voltage spark circuit presents an electric shock
that is not a pure substance.
hazard, adequate interlock and shielding must be employed to
prevent contact.
8.4 The moisture content of the test sample should not
7.5 All enclosures containing electrical equipment should
exceed 5 % in order to avoid test results being noticeably
be connected to a common ground, and shielded cables should
influenced.
be used.
NOTE 3—There is no single method for determining the moisture
7.6 The operator should work from a protected location in
content or for drying the sample. ASTM lists many methods for moisture
case of vessel or electrical failure.
determination in the Annual Book of ASTM Standards. Sample drying is
equally complex due to the presence of volatiles, lack of or varying
8. Sampling and Test Specimen
porosity such as coal (see Test Methods D 3173 and D 3175), and
8.1 It is not practical to specify a single method of sampling
sensitivity of the sample to heat. Therefore, each must be dried in a
dust for test purposes since the character of the material and its
manner that will not modify or destroy the integrity of the sample.
Hygroscopic materials must be desiccated.
available form affect selection of the sampling procedure.
Generally accepted sampling procedures should be used as
9. Calibration and Standardization
described in STP 447A.
8.2 Tests may be run on an as-received sample. However,
9.1 Calibration of the air dispersion system should be made
due to possible accumulation of fines at some location in a
to establish proper air flow into the dispersion cup and
processing system, it is recommended that the test sample be at
combustion bomb. A cylindrical calibration chamber as de-
least 95 % minus 200 mesh (74 μm).
tailed in Fig. A1.13 is secured to the combustion chamber base
after setting the mushroom four turns counterclockwise from
NOTE 1—It may be desirable in certain instances to conduct dust
its closed position. A pressure transducer is connected to the
explosion tests on materials as sampled from a process, since (a) process
dust streams may contain a wide range of particle sizes or have a calibration chamber. The air (100 psig, 690 kPa) in the
well-defined specific moisture content making it desirable to test the
dispersion reservoir is then released and a pressure-time record
material in the as-received state, (b) materials consisting of a mixture of
of the event is obtained from the appropriate measuring
chemicals may be selectively separated on sieves making it desirable to
equipment. The maximum pressure and rate of pressure rise
test the as-received material, (c) certain fibrous materials which may not
determined from this record should be within the following
pass through a relatively coarse screen may produce dust explosions if
limits:
tested in the as-received state, (d) when a material is tested in the
as-received state it should be recognized that the test results may not
9.1.1 Maximum Pressure: 256 2 psig (172 6 14 kPa)
represent the most severe dust explosion possible. Any process change
9.1.2 Maximum Rate of Pressure Rise: 975 6 50 psi/s
resulting in a higher fraction of fines than normal or drier product than
(6.726 0.34 MPa/s).
normal will increase the potential hazard from dust explosions.
9.2 A standardization of the equipment before starting the
8.3 To achieve this particle fineness ($95 % minus 200
3 3
testing and at the end of the day with 0.75 oz/ft (kg/m )of
mesh) the sample may be ground or pulverized or it may be
lycopodium is necessary. The test equipment must read a
sieved.
pressure of 100 6 12 psig (690 6 83 kPa) and rate of 6300
NOTE 2—The operator should consider the thermal stability of the dust psi/s 6 20 % before using.
E 789
10. Procedure
10.1 Separate the steel combustion chamber from the dis-
persion cup base. Clear the dispersion system with several
blasts of air. Remove the spark electrodes and insulators from
the tube and dry clean them with sandpaper, steel wool, emery
cloth, or similar material. Recheck the electrodes and repoint as
necessary. Clean the inside of the tube with a wire brush or
similar device and remove the loosened residue from the
preceding test with a blast of high-pressure air or a vacuum
cleaner. Thoroughly clean the dispersion cup, mushroom, and
pressure transducer.
10.2 Remove the mushroom and check the mushroom insert
(Fig. A1.7) making sure it is flush with the top of the air
dispersion cup (A1.6). Reinsert the mushroom by turning it
clockwise until the cap is snug against the dispersion cup; then
turn the mushroom counterclockwise four complete turns.
10.3 Spread a weighed amount of dust into a uniformly thin
layer around the bottom of the dispersion cup. Determine
concentration by dividing the weight of dust used by the
FIG. 2 Pressure Versus Time—Data Analysis
3 3
volume of the steel combustion chamber 75 in. (0.00123 m ).
Explosion tests are normally made at calculated dust concen-
3 3 12.1.2 Size distribution (sieve analysis) of the sample as
trations of 0.1, 0.2, 0.5, 1.0, and 2.0 oz/ft (or kg/m ).
received and as tested.
NOTE 4—To convert gram weight per 75 in. to ounces per cubic feet
12.1.3 Moisture content of the as-received and as-tested
multiply by 0.813.
material.
10.4 Secure the electrodes in the steel combustion chamber 12.1.4 Maximum pressure for all concentrations and par-
and adjust to a ⁄4)-in. (6.4-mm) gap. ticle sizes tested. Curves showing these data may also be
10.5 Place the O-ring on top of the dispersion cup, and lock included (see Fig. 3).
the steel combustion chamber in place with the hinged bolts.
13. Precision
10.6 Secure the O-ring and top assembly to the combustion
chamber by hand-tightening the locking ring handle. 13.1 The following criteria should be used for judging the
10.7 Adjust the air dispersing pressure in the 3-in. acceptability of results.
(0.00005-m ) reservoir to 100 psig (690 kPa). 13.1.1 Maximum Pressure:
10.8 Ensure that the dispersion system is airtight. 13.1.1.1 Repeatability—The average of duplicate tests
10.9 Attach the electrical source to the electrodes and set the should be considered suspect if they differ by more than 20 %.
desired recorder speed. 13.1.1.2 Reproducibility—The average of duplicate tests
10.10 Put shield in place. obtained by each of several laboratories should be considered
10.11 Actuate the firing circuit to conduct the test (see A1.6 suspect if they differ by more than 22 %.
for a description of the sequence of events following activation
NOTE 5—Precision is based on lycopodium reported in ASTM. Other
of the firing circuit).
materials may give results outside the above criteria.
11. Calculation
11.1 A pressure versus time trace for an explosion is
typically of the form given in Fig. 2, from which (1) maximum
pressure and (2) maximum rate of pressure rise can be
deduced.
11.2 The data points constituting the above curve can be
captured using high-speed analog to digital data capture
techniques and then the logged data can be analyzed.
11.3 It is important that the captured waveform is free from
noise and spikes which could cause errors during the analysis.
Filtering techniques in the data capture hardware should be
employed and additionally some software smoothing of the
data can be undertaken.
12. Report
12.1 Report the following information:
12.1.1 Complete identification of the material tested, includ-
FIG. 3 Maximum Pressure and Rates of Pressure Rise Developed
ing source, code numbers, forms, color, previous history. by Explosions of Zirconium Dust in the Hartmann Equipment
E 789
14. Keywords
14.1 dust explosion; dust ignition
ANNEXES
(Mandatory Information)
A1. METHOD OF OPERATION OF HARTMANN EQUIPMENT AND DETAILED DRAWINGS
A1.1 Fig. 1 is a schematic of the test apparatus and A1.3.1 The maximum pressure that can be developed in the
associated electronic instrumentation. Detailed constructional closed combustion tube from the introduction of the dispersing
drawings of each part of the apparatus are shown in Figs. air is 6.5 psig (45 kPa). Due to the rapid development of the
A1.1-A1.13. Part numbers and the figure for the drawings of explosion and action of the check valve, the pressure from the
each part are listed in Table A1.1. To serve as a guide, auxiliary dispersing air at the time of ignition is normally 2 to 3 psig (14
TABLE A1.1 Listing of Constructional Drawings for the Hartmann Apparatus
NOTE 1—Make combustion chamber base, six of one piece.
NOTE 2—Combustion chamber assembly, Parts 1, 12, 16, and 6, may be chromium-plated inside and outside except threads of Parts 12 and 16.
NOTE 3—All sliding fits shall be Class 3 medium fit ASA classification of fits. Nominal allowances are indicated.
Fig. Part Number To Fit Method of
Nomenclature Material
No. No. Required Part No. Assembling
Fig. A1.1 1 Hartmann combustion chamber 1 Seamless carbon mechanical steel . .
tubing
Fig. A1.2 . Hartmann base support and air control system 1 . 1 .
Fig. A1.3 2 Pressure transducer adapter ring 1 brass 1 slide fit
Fig. A1.3 3 Locking ring 1 brass 1 12 threads per inch
Fig. A1.3 4 Locking ring handle 3 brass 3 silver solder
Fig. A1.3 5 Electrode holder locknut wrench 1 steel 18 .
Fig. A1.4 6 Combustion chamber base 1 steel 1 12 threads per inch
Fig. A1.5 7 Holding lug screws 4 hardened steel 8 ⁄4-20 thread
Fig. A1.5 8 Holding lug base 4 steel 10 slide fit
Fig. A1.6 9A Dispersion cup 1 brass 6 slide fit
Fig. A1.7 9B Mushroom 1 brass 9C 2-56 thread
Fig. A1.7 9C Mushroom insert 1 brass 9A snug fit
Fig. A1.8 10 Dispersion cup base 1 brass 9A 6-
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