SIST EN 13821:2003
(Main)Potentially explosive atmospheres - Explosion prevention and protection - Determination of minimum ignition energy of dust/air mixtures
Potentially explosive atmospheres - Explosion prevention and protection - Determination of minimum ignition energy of dust/air mixtures
This EN specifies a method of test to determine the minimum ignition energy of a dust/air mixture by an electrically generated spark. It is intended that the dust be tested in a form representing conditions of actual use so that assessment of the hazard present can be made. Ignition energies determined by this method would be compared with ignition by a pointed source. This EN is applicable to the determination of the minimum ignition energy of a combustible dust dispersed in air, referred to hereafter as a "dust/air mixture".
Explosionsfähige Atmosphären - Explosionsschutz - Bestimmung der Mindestzündenergie von Staub/Luft-Gemischen
Diese Europäische Norm legt ein Prüfverfahren zur Bestimmung der Mindestzündenergie eines Staub/Luft-Gemisches durch einen elektrisch erzeugten Funken fest.
Dieses Prüfverfahren ist nicht geeignet für die Anwendung bei Sprengstoffen, Schießpulvern, Dynamit, Stoffen, die keinen Sauerstoff zur Verbrennung benötigen, pyrophoren Stoffen, oder Stoffen oder Stoffgemischen, die sich gegebenenfalls ähnlich verhalten können wie die vorgenannten Stoffe. Wenn irgendein Zweifel über das Vorhandensein einer Gefährdung auf Grund von Explosivstoffeigenschaften des Staubes besteht, sollten Fachleute zu Rate gezogen werden.
WARNHINWEIS - Es ist wichtig, Vorsichtsmaßnahmen gegen Brand und Explosionsgefahr und/oder die Gefahr durch giftige Verbrennungsprodukte zu ergreifen, um die Gesundheit des Prüfpersonals zu schützen.
Atmospheres explosibles - Prévention et protection contre l'explosion - Détermination de l'énergie minimale d'inflammation des mélanges poussiere/air
La présente norme européenne spécifie une méthode d'essai pour déterminer l'énergie minimale d'inflammation d'un mélange poussiere/air sous l'effet d'une étincelle générée électriquement.
La méthode d'essai ne convient pas aux explosifs reconnus, poudre, dynamite, aux explosifs qui ne requierent pas d'oxygene pour leur combustion, aux substances pyrophoriques ou aux substances ou mélanges de substances qui peuvent, dans certaines circonstances, se comporter de maniere similaire. Lorsqu'il existe un doute sur l'existence d'un phénomene dangereux en raison de propriétés explosives, il convient de prendre l'avis des experts.
NOTE La Directive 94/9/CE relative aux équipements et aux systemes de protection destinés a etre utilisés dans des atmospheres explosibles peut etre applicable au type de machine ou d'équipement couvert par la présente Norme européenne. La présente norme n'est pas destinée a fournir des moyens de satisfaire aux exigences essentielles de santé et de sécurité de la Direction 94/9/CE.
AVERTISSEMENT - Des précautions doivent etre prises pour protéger la santé du personnel effectuant les essais contre le risque d'incendie, d'explosion et/ou les effets, y compris toxiques, de la combustion. La conformité avec la présente norme européenne en elle-meme ne confere pas l'immunité vis-a-vis des obligations légales.
Potencialno eksplozivne atmosfere - Protieksplozijska zaščita - Ugotavljanje najmanjših vžignih energij zmesi prahu z zrakom
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 13821:2003
01-februar-2003
3RWHQFLDOQRHNVSOR]LYQHDWPRVIHUH3URWLHNVSOR]LMVND]DãþLWD8JRWDYOMDQMH
QDMPDQMãLKYåLJQLKHQHUJLM]PHVLSUDKX]]UDNRP
Potentially explosive atmospheres - Explosion prevention and protection - Determination
of minimum ignition energy of dust/air mixtures
Explosionsfähige Atmosphären - Explosionsschutz - Bestimmung der
Mindestzündenergie von Staub/Luft-Gemischen
Atmospheres explosibles - Prévention et protection contre l'explosion - Détermination de
l'énergie minimale d'inflammation des mélanges poussiere/air
Ta slovenski standard je istoveten z: EN 13821:2002
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
SIST EN 13821:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 13821:2003
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SIST EN 13821:2003
EUROPEAN STANDARD
EN 13821
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2002
ICS 13.230
English version
Potentially explosive atmospheres - Explosion prevention and
protection - Determination of minimum ignition energy of dust/air
mixtures
Atmosphères explosibles - Prévention et protection contre Explosionsfähige Atmosphären - Explosionsschutz -
l'explosion - Détermination de l'énergie minimale Bestimmung der Mindestzündenergie von Staub/Luft-
d'inflammation des mélanges poussière/air Gemischen
This European Standard was approved by CEN on 16 October 2002.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13821:2002 E
worldwide for CEN national Members.
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SIST EN 13821:2003
EN 13821:2002 (E)
Contents
page
Foreword.3
1 Scope .3
2 Normative references .3
3 Terms and definitions.3
4 Test apparatus.4
4.1 Spark generation circuit.4
4.2 Test vessel.5
5 Test sample .5
6 Test procedure .5
6.1 Test description .5
6.2 Calibration .6
6.3 Conformity.7
6.3.1 Conformity tests.7
6.3.2 Criteria for conformity.7
6.4 Test report .8
Annex A (normative) Descriptions of spark generating systems .9
A.1 General.9
A.2 Triggering by high-voltage relay, using a two-electrode system .9
A.3 Triggering by electrode movement, using a two-electrode system .10
A.4 Triggering by auxiliary spark, using 3-electrode system .11
A.5 Triggering by voltage increase, using two-electrode system.12
A.6 Triggering by transformer, using two-electrode system .13
A.7 Example of a test apparatus .14
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other
provisions of EU Directives. .15
Bibliography .16
2
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SIST EN 13821:2003
EN 13821:2002 (E)
Foreword
This document EN 13821:2002 has been prepared by Technical Committee CEN /TC 305 "Potentially explosive
atmospheres - Explosion prevention and protection", the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by May 2003, and conflicting national standards shall be withdrawn at the latest by
May 2003.
This document has been prepared under a mandate given to CEN by the European Commission and the European
Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this document.
Annex A is normative.
This document includes a Bibliography.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard : Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland and the United Kingdom.
1 Scope
This European Standard specifies a method of test to determine the minimum ignition energy of a dust/air mixture by
an electrically-generated spark.
The test method is not suitable for use with recognised explosives, gunpowder, dynamite, explosives which do not
require oxygen for combustion; pyrophoric substances, or substances or mixtures of substances which can under
some circumstances behave in a similar manner. Where any doubt exists about the existence of a hazard due to
explosive properties, expert advice should be sought.
WARNING — It is essential that precautions are taken to safeguard the health of personnel conducting the
tests against the risk of fire, explosion and/or toxic effects, of combustion products.
2 Normative references
There are no normative references.
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
dust
small solid particles that are able to remain suspended in air for some time
NOTE Normally maximum particle sizes will not exceed 500 μm. This definition includes what are defined in ISO 4225 as
'dust' and 'grit'
3
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EN 13821:2002 (E)
3.2
combustible dust
dust able to undergo an exothermic reaction with air when ignited
3.3
explosive dust/air mixture
mixture of dust with air in which, after ignition has occurred, combustion spreads to the entire unburned mixture
3.4
spark discharge
transient discrete electric discharge which takes place between two electrodes which are at different potentials. The
discharge bridges the gap between the conductors in the form of a single ionisation channel
3.5
minimum ignition energy of an explosive dust/air mixture
lowest electrical energy stored in a capacitor which upon discharge is just sufficient to effect ignition of the most ignit-
able mixture of a given dust under specific test conditions
3.6
ignition
propagation of a sustainable flame away from the spark discharge position
3.7
ignition delay time
time between the onset of dispersion of the dust sample into a cloud and the occurrence of the spark discharge
3.8
(temperature, pressure)
test conditions
air having a temperature in the range from 20 °C to 25 °C and a pressure in the range from 0.8 bar to 1.1 bar,
absolute
4 Test apparatus
4.1 Spark generation circuit
Annex A describes some suitable forms of circuit for spark generation all of which shall have the following charac-
teristics:
a) inductance of discharge circuit: from 1 mH to 2 mH except when the data is to be used for the assessment of
electrostatic hazards. Then the total inductance of the discharge circuit shall not exceed 25 μH;
b) ohmic resistance of discharge circuit: as low as possible and not more than 5 W;
c) electrode material: tungsten, stainless steel, brass, or copper;
d) electrode shaft diameter: 2.0 – 0.5 mm;
e) electrode shape: pointed;
f) electrode gap: ‡ 6 mm (minimum);
g) capacitance of electrode arrangement: as low as possible. If the parasitic capacitance of the electrode system
is significant compared with the discharge capacitance, it shall be taken into account;
h) insulation resistance between electrodes: sufficiently high to prevent leakage currents.
NOTE For low spark energies together with pointed electrodes a significant fraction of the energy in the capacitance can
drain away as corona discharges prior to the spark discharge.
4
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SIST EN 13821:2003
EN 13821:2002 (E)
4.2 Test vessel
The recommended test equipment is the Hartmann apparatus described in references 7,8 and 10 in bibliography. This
apparatus is shown in A.7.
NOTE The minimum ignition energy is independent of the volume (V ‡ 1 l). Therefore it can also be determined in the 20-l-
3
sphere or in the 1 m -vessel.
Other vessels may be used provided that the conformity requirements according to 6.3 are met.
5 Test sample
The minimum ignition energy decreases with decreasing particle size. Therefore the particle size distribution shall be
determined for the sample as tested and shall be indicated in the test report.
The minimum ignition energy decreases with decreasing moisture content. Therefore the moisture content shall be
determined for the sample as tested and shall be indicated in the test report.
NOTE 1 Where the particle sizes of the material in the plant are not known, tests should be carried out on dust samples of
particle sizes e.g. less than 63 mm.
NOTE 2 The size of the dust particles can be reduced by the dispersion process. In cases, where this effect can be
important, its magnitude can be evaluated by measuring the particle size distribution after dispersion (without ignition).
NOTE 3 Grinding can alter the particle shape and surface condition, and sieving can alter the proportion of inert in the
sample. A rough classification of the shape of the dust particles may also be necessary („spherical“, „flat“ or „fibrous“).
NOTE 4 Where the moisture content in the plant is not known, the sample should be carefully dried, e.g. at 50 °C under
vacuum, or at 75 °C and atmospheric pressure until the sample weight has reached a constant value.
6 Test procedure
6.1 Test description
The dust to be tested is dispersed in air at test conditions (specified in 3.8) in the test-apparatus, and the dust cloud is
subjected to a spark discharge from a capacitor.
The energy value of the discharge is calculated from the equation
2
E = 0,5 C ⋅ U (1)
where:
E is the stored energy in joules [J];
C is the total capacitance of the discharge circuit in farads [F] and
U is the voltage of the capacitor in volts [V].
NOTE 1 Further information relevant to the calculation of spark energies is contained in annex A.
NOTE 2 The following possible influences on the test should be considered:
dust/air mixture dynamics/turbulence (a function of ignition delay time and dispersing pressure etc.);
dust concentration;
voltage of the capacitor;
capacitance of the discharge circuit capacitor;
inductance of the discharge circuit;
5
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SIST EN 13821:2003
EN 13821:2002 (E)
ohmic resistance of the discharge circuit;
materials and dimensions of the electrodes and the gap between the electrodes.
The minimum ignition energy is a function of the dust/air mixture dynamics/turbulence and the dust concentration. The
minimum ignition energy shall be measured at the optimum dust concentration and the lowest turbulence level
experimentally attainable. The turbulence level is reduced by extending the ignition delay time until as long a delay
time as is feasible for the apparatus is determined.
The optimum dust concentration and the lowest turbulence level cannot be obtained in one step. Therefore an
iterative procedure is required of which the main steps are as follows:
Step 1
Start with a value of ignition energy that will reliably cause ignition of a given concentration in air of the dust being
tested. Reduce the spark energy in steps (e.g. by 50%) at the given dust concentration until the dust cloud does no
longer ignite in any of 10 tests at a given energy.
Step 2
Continue the procedure varying the dust concentration at the lowest energy found in Step 1. If for any dust
concentration an ignition occurs, then repeat Step 1 at that concentration.
Step 3
Repeat the procedure by this combination of spark energy and dust concentration varying the delay time (turbulence)
until the maximum energy (E ) is found where no ignition occurs.
1
The minimum ignition energy MIE lies between the highest energy, E , at which ignition fails to occur in 10 successive
1
attempts to ignite the dust/air mixture, and the lowest energy, E , at which ignition occurs within up to 10 successive
2
attempts.
E < MIE < E (2)
1 2
6.2 Calibration
At regular intervals (at least every 12 months, or following any significant maintenance or repair) the apparatus shall
be calibrated by:
a) checks of components
1) energy of the discharge: capacitance of capacitors and voltage applied/generated;
2) inductance of the circuit;
3) ohmic resistance of the circuit;
4) capacitance of the circuit;
5) the dust dispersion systems: delay time and dispersion pressure.
b) calibration of total system
Calibration shall be carried out using one of the following tests:
internal calibration with at least one reference dust the MIE of which is known. The results of the E -value (see
S
section 6.3) shall differ by less than a factor of 3 to prove the positive outcome of the calibration.
comparative measurement of minimum ignition energy with at least one other laboratory with at least one
reference dust. The results of the E -value (see section 6.3) shall differ by less than a fa
...
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