Determination of the spontaneous ignition behaviour of dust accumulations

This European Standard specifies analysis and evaluation procedures for determining self-ignition temperatures (TSI) of combustible dusts or granular materials as a function of volume by hot storage experiments in ovens of constant temperature. The specified test method is applicable to any solid material for which the linear correlation of lg (V/A) versus the reciprocal self-ignition temperature 1/TSI (with TSI in K) holds (i.e. not limited to only oxidatively unstable materials).
This European Standard is not applicable to the ignition of dust layers or bulk solids under aerated conditions (e.g. as in fluid bed dryer).
This European Standard shall not be applied to dusts like recognised explosives that do not require atmospheric oxygen for combustion, nor to pyrophoric materials.
NOTE   Because of regulatory and safety reasons "recognised explosives" are not in the scope of this European Standard. In spite of that, substances which undergo thermal decomposition reactions and which are not "recognised explosives" but behave very similarly to self-ignition processes when they decompose are in the scope. If there are any doubts as to whether the dust is an explosive or not, experts should be consulted.

Bestimmung des Selbstentzündungsverhaltens von Staubschüttungen

Dieses Dokument legt Prüf- und Auswerteverfahren zur Bestimmung der Selbstentzündungstemperaturen (TSI) brennbarer Stäube oder Schüttgüter als Funktion des Volumens fest. Das geschieht durch Warmlagerungsuntersuchungen in Öfen bei konstanter Ofentemperatur. Das spezifische Prüfverfahren ist auf jeden Feststoff anwendbar, für den die Theorie der Wärmeexplosion nach A.2 gilt (d. h. nicht begrenzt auf ausschließlich oxidativ instabile Stoffe).
Die spezifische Prüfung ist auf jeden Staub oder jedes Schüttgut anwendbar, das primär mit Luftsauerstoff reagiert. Aus Sicherheitsgründen wird diese Prüfung nicht mit Stoffen durchgeführt, die mit festen/flüssigen Oxidantien gemischt sind (z. B. Schießpulver, Thermit, mit flüssigem Sauerstoff imprägniertes Holz) oder mit Stoffen, bei denen heftige nicht oxidative Reaktionen entstehen könnten (z. B. Peroxide, Explosivstoffe). Jedoch dürfen im Einzelfall einige Arten von Stoffen geprüft werden, bei denen nicht oxidative Reaktionen entstehen können (z. B. nicht heftige exotherme Zersetzungsreaktionen), vorausgesetzt, dass zusätzliche Sicherheitsvorkehrungen getroffen werden. Bei Zweifeln über Gefahren aufgrund der Eigenschaften des zu untersuchenden Stoffes (z. B. ob er toxisch oder explosiv ist), wird der Rat eines Expertes eingeholt.
Dieses Dokument ist nicht anzuwenden für die Entzündung von Staubschichten oder Schüttungen unter durchlüfteten Bedingungen (wie z. B. in einem Fließbett-Trockner).

Détermination de l'aptitude à l'auto-inflammation des accumulations de poussières

Le présent document spécifie des modes opératoires d’analyse et d’évaluation permettant de déterminer les températures d’auto-inflammation (TAI) de poussières combustibles ou de matériaux granulaires en fonction de leur volume par des essais en étuve isotherme dans des étuves à température constante. La méthode d’essai spécifiée s’applique à tout matériau solide pour lequel la théorie de l’explosion thermique, selon l’Article A.2, se vérifie (c’est-à-dire que son applicabilité ne se limite pas aux seuls matériaux instables par oxydation).
L’essai spécifié s’applique à toute poussière ou tout matériau granulaire réagissant principalement avec l’oxygène de l’air. Pour des raisons de sécurité, cet essai ne doit pas être utilisé avec des matériaux mélangés à des oxydants solides/liquides (tels que de la poudre noire, des thermites ou du bois imprégné d’oxygène liquide) ou des matériaux pouvant subir de violentes réactions non oxydantes (par exemple, peroxydes, explosifs). Certains types de matériaux subissant des réactions non oxydantes (telles que des réactions de décomposition exothermiques non violentes) peuvent toutefois être soumis à essai au cas par cas, à condition de prendre des mesures de sécurité supplémentaires. En cas de doute concernant l’existence d’un danger lié aux propriétés du matériau d’essai (toxiques ou explosives, par exemple), il convient de consulter l’avis d’experts.
Le présent document n’est pas applicable à l’inflammation des couches de poussière ou des solides en vrac dans des conditions aérées (par exemple, dans un sécheur en lit fluidisé).

Določanje lastnosti samovžiga usedlih plasti prahu

General Information

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Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
23-Dec-2020
Completion Date
23-Dec-2020

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SLOVENSKI STANDARD
SIST EN 15188:2021
01-april-2021
Nadomešča:
SIST EN 15188:2007
Določanje lastnosti samovžiga usedlih plasti prahu
Determination of the spontaneous ignition behaviour of dust accumulations
Bestimmung des Selbstentzündungsverhaltens von Staubschüttungen

Détermination de l'aptitude à l'auto-inflammation des accumulations de poussières

Ta slovenski standard je istoveten z: EN 15188:2020
ICS:
13.220.40 Sposobnost vžiga in Ignitability and burning
obnašanje materialov in behaviour of materials and
proizvodov pri gorenju products
13.230 Varstvo pred eksplozijo Explosion protection
SIST EN 15188:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 15188:2021
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SIST EN 15188:2021
EN 15188
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2020
EUROPÄISCHE NORM
ICS 13.230 Supersedes EN 15188:2007
English Version
Determination of the spontaneous ignition behaviour of
dust accumulations

Détermination de l'aptitude à l'auto-inflammation des Bestimmung des Selbstentzündungsverhaltens von

accumulations de poussières Staubschüttungen
This European Standard was approved by CEN on 18 October 2020.

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 CEN-CENELEC 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 CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 15188:2020 E

worldwide for CEN national Members.
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SIST EN 15188:2021
EN 15188:2020 (E)
Contents Page

European foreword ...................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

4 Test apparatus ................................................................................................................................................. 6

4.1 Sample baskets ................................................................................................................................................ 6

4.2 Determination of Basket Volume .............................................................................................................. 7

4.3 Oven and test conditions .............................................................................................................................. 7

4.4 Thermocouples ................................................................................................................................................ 9

4.5 Temperature recording equipment ......................................................................................................... 9

5 Preparation of dust samples ....................................................................................................................... 9

6 Procedure ........................................................................................................................................................ 10

6.1 Experimental Procedure ............................................................................................................................ 10

6.2 Evaluation of tests ........................................................................................................................................ 11

6.3 Calibration of thermocouples ................................................................................................................... 12

7 Test report ....................................................................................................................................................... 12

8 Precision .......................................................................................................................................................... 13

8.1 General.............................................................................................................................................................. 13

8.2 Uncertainty of extrapolation to larger volumes ................................................................................ 13

8.3 Uncertainty of single-basket-test (10 cm basket) ............................................................................. 14

Annex A (normative) Theoretical Basis to Determinations and Extrapolations .................................. 15

Annex B (informative) Extrapolation of induction times .............................................................................. 21

Annex C (informative) Extrapolation to Temperatures or Volumes of Interest by Numerical

solution of Fourier’s equation .................................................................................................................. 23

Annex D (informative) Alternative method for running tests adiabatically and interpreting

the results ........................................................................................................................................................ 26

Annex E (normative) Safety Precautions ............................................................................................................. 30

Annex F (informative) Significant Changes between this European Standard and

EN 15188:2007 .............................................................................................................................................. 31

Annex ZA Annex ZA (informative) Relationship between this European Standard and the

Essential Requirements of EU Directive 2014/34/EU ..................................................................... 33

Bibliography ................................................................................................................................................................. 34

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EN 15188:2020 (E)
European foreword

This document (EN 15188:2020) 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 June 2021, and conflicting national standards shall be

withdrawn at the latest by December 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN 15188:2007.

This document has been prepared under a standardization request given to CEN by the European

Commission and the European Free Trade Association, and supports essential requirements of EU

Directive 2014/34/EU.

For relationship with EU Directive 2014/34 EU, see informative Annex ZA, which is an integral part of

this document.

According to the CEN-CENELEC Internal Regulations, the national standards organisations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
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Introduction

The self-ignition behaviour of dusts and granular materials and their mixtures depends on their

chemical composition as well as on related substance and bulk properties. It also depends on the size

and geometry of the body of material, and, last but not least on the ambient temperature.

The reason for self-heating (with possible self-ignition) is that the surface molecules of combustible

dust or granular materials undergo exothermic reactions with air or other oxidising atmospheres

transported into the void volume between the particles even at normal ambient temperatures. Any heat

then released will cause the temperature of the reactive system to rise, thus accelerating the reaction of

additional molecules with oxygen, etc. A heat balance involving the heat produced inside the bulk

(quantity and surface of reactive surface molecules, specific heat producing rate) and the heat loss to

the surroundings (heat conductivity and dimension of the bulk, heat transfer coefficient on the outside

surface of the bulk and the size of the latter) is decisive as to whether a steady-state temperature is

reached at a slightly higher temperature level (the heat loss terms are larger than the heat production

term), or whether temperatures in the bulk will continue to rise up to self-ignition of the material, if

heat transport away from the system is insufficient (in this case the heat production term is larger than

all heat losses).

The experimental basis in this document for describing the self-ignition behaviour of a given dust or

granular material is the determination of the self-ignition temperatures (T ) of differently sized bulk

volumes by isoperibolic hot storage experiments (storage at constant oven temperatures) in

commercially available ovens. The results thus measured reflect the dependence of self-ignition

temperatures upon volume of the accumulation.

Different evaluation procedures – described in Annex A – allow interpolation and extrapolation, to

characterize the self-ignition behaviour of deposits of a different scale and of different bulk geometric

shapes. Primary method is the evaluation based on the thermal explosion theory according to Frank-

Kamenetskii (A.2) and Thomas (A.3).

Interlaboratory tests have shown, that it is necessary to provide prescribed test conditions, e.g. by

installation of a mesh wire screen into the oven, surrounding the dust samples and the thermocouples.

In this way the spread of results will be minimized. If it is possible based on suitable thermo-analytic

test procedures (adiabatic, isothermal or dynamic tests) to derive a reliable formal kinetic model, which

describes the heat production of the substance as a function of temperature, then the volume

dependency of the self-ignition temperature may be calculated according to the methods described in

Annex A.
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EN 15188:2020 (E)
1 Scope

This document specifies analysis and evaluation procedures for determining self-ignition temperatures

(T ) of combustible dusts or granular materials as a function of volume by hot storage experiments in

ovens of constant temperature. The specified test method is applicable to any solid material for which

the thermal explosion theory according to A.2 holds (i.e. not limited to only oxidatively unstable

materials).

The specified test is applicable to any dust or granular material that reacts primarily with oxygen from

the air. For safety reasons, this test is not used with materials mixed with solid/liquid oxidant (e.g.

gunpowder, thermites, wood impregnated with liquid oxygen) or materials that could undergo violent

non-oxidative reactions (e.g. peroxides, explosives). On a case by case basis, some types of materials

undergoing non-oxidative reactions (e.g. non-violent exothermic decomposition reactions) may be

however tested provided that additional safety precautions are taken. Where any doubt exists about the

existence of hazard due to the properties of the test material (e.g. toxic or explosive), expert advice is

sought.

This document is not applicable to the ignition of dust layers or bulk solids under aerated conditions

(e.g. as in fluid bed dryer).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 1127-1:2019, Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts

and methodology

EN 13237:2012, Potentially explosive atmospheres - Terms and definitions for equipment and protective

systems intended for use in potentially explosive atmospheres
3 Terms and definitions

For the purposes of this document, the following terms and definitions given in EN 13237:2012,

EN 1127-1:2019 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
self-ignition temperature
highest temperature at which a given volume of dust just does not ignite
Note 1 to entry: Self-ignition temperature is expressed in °C.
3.2
oven temperature

arithmetic mean of the measured values of two thermocouples, both freely installed in an oven at a

distance of 5 cm to the surface of the dust sample
Note 1 to entry: Oven temperature is expressed in °C.
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EN 15188:2020 (E)
3.3
sample temperature
temperature measured at the centre of the dust sample using a thermocouple
Note 1 to entry: Sample temperature is expressed in °C.
3.4
induction time

interval of time between reaching the storage temperature and start of ignition (defined by the

inflection point, see Figure 3 case C)
Note 1 to entry: Induction time is expressed in h.
3.5
ignition
initiation of combustion
[SOURCE: EN ISO 19353:2019, 3.20]
3.6
bulk density
sample mass divided by the determined volume of the basket
3.7
dust
finely divided solid particles, up to 500 µm in nominal size
3.8
granules
discrete particles larger than 500 µm
4 Test apparatus
4.1 Sample baskets

The samples have to be filled into mesh wire baskets of different volumes. The baskets have to be open

at the top and closed at the bottom. They shall consist of two layers of narrow-meshed wire net, made of

e.g. stainless steel. The width of the mesh for the inner sample container has to be chosen in such a way

that the dust cannot fall through the mesh, but the diffusion of the oven air into the dust sample is not

hindered (e.g. mesh opening of 0,05 mm). The outer basket should be made from coarser mesh wire

(e.g. mesh opening of 0,5 mm). The outer basket defines the test volume therefore the inner basket

should be tightly fitting within, such that it does not distort when inserted. Recommended shapes of the

mesh wire baskets are that of a cube, or that of a cylinder with a height to diameter ratio of 1.

To allow an assessment of the self-ignition behaviour of larger sizes of dust accumulations than the

laboratory-scale, by extrapolation, at least four mesh wire baskets of different volumes have to be used

for the tests.

The smallest volume should normally be in the order of 100 cm and the largest should normally not be

smaller than approximately 1 000 cm . The volume ratio of the baskets should be approx. 1 : 1,7 : 5: 8;

e.g. cubes with edge length of 5 cm, 6 cm, 8,5 cm and 10 cm.
NOTE 1 Larger baskets are acceptable when sufficient material is available.

If only a limited amount of sample material is available, even smaller baskets may be used.

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EN 15188:2020 (E)

NOTE 2 For the sake of comparing products with respect to their self-ignition behaviour in devices or

apparatus, where the sizes of the dust accumulations are limited for the reason of a specific design, often the

3 3

determination of the self-ignition temperature for a basket of 400 cm or 1 000 cm is sufficient.

4.2 Determination of Basket Volume

The volume of the sample baskets shall be determined by using suitable material consisting of

sufficiently small particles of spherical shape having a smooth surface and therefore of a known and

stable bulk density, e.g. glass beads with a diameter of approx. 0,3 mm. The baskets are filled with the

suitable material; any surplus material from the upper margin has to be removed. The basket is

weighed before and after filling. The volume results from the weight of the filled in material with known

bulk density (mean value of at least two measurements).
4.3 Oven and test conditions

Commercially available ovens (natural and forced convection) can be used. They shall have an air inlet

opening in the lower section and an air outlet opening in the upper section and should be controllable

in a temperature range from 35 °C to 300 °C. After reaching the test temperature the oven temperature

shall be stable over time within a range of ± 1 K.

The temperature field surrounding the sample shall exhibit maximum spatial temperature differences

of 4 K at an oven temperature of 120 °C. To determine the differences the temperature shall be

measured on 6 sides of a 10 cm sample cube in a distance of 5 cm, respectively. This measurement shall

be performed after installing the set-up and if the set-up (including hot storage oven) is changed. The

measurement shall be repeated once a year. Radiative heat transfer across the sample surfaces should

be minimized.

To achieve these conditions a mesh wire screen shall be installed into the oven. The minimum distance

between the screen and the oven walls shall be 5 cm. The screen consists of mesh wire with mesh

opening of e.g. 0,5 mm. The screen shall be equipped with a front door and a sample holder, see

Figure 1. The sample baskets shall freely hang in the oven. Additional metal sheets (thickness 0,25 mm

to 0,5 mm) can be installed at half height and on top to achieve the above conditions. The width of the

sheets shall be chosen in such a way, that the largest sample basket, hanging in the screen, is covered.

For measuring the oven temperature two thermocouples have to be installed on opposite sides at a

distance of 5 cm to the sample. The thermocouples have to be re-positioned for sample baskets of

differing sizes. The minimum distance between the thermocouples and the wall of the screen is 2,5 cm,

see Figure 2.
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SIST EN 15188:2021
EN 15188:2020 (E)
Key
1 front door
2 metal sheets (optional)
3 mesh wire
4 sample holder
5 thermocouples for measuring oven temperature
6 thermocouple for measuring sample temperature
7 mesh wire container with dust sample
Figure 1 — Mesh wire screen to be installed into the heating oven
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SIST EN 15188:2021
EN 15188:2020 (E)
Figure 2 — Position of sample and thermocouples

Alternative test arrangements can be used to provide the specified test conditions. In this case, the

uncertainty specified in Clause 8 may be not applicable.
4.4 Thermocouples

Both for measuring the sample temperature as well as for measuring the oven temperature, sheathed

thermocouples with an external diameter of e.g. 1 mm are recommended.
4.5 Temperature recording equipment

Appropriate data acquisition may be used for measuring and recording signals of the thermocouples.

5 Preparation of dust samples

To investigate situations occurring in practice a representative sample should be used (produced by the

operating conditions of the process). The sample characteristics shall be recorded in the test report.

The bulk density of the sample should be adjusted to the respective practical conditions (if known).

The bulk density shall be determined in the baskets and shall not vary by more than ± 2 % in the test

series.

Due to the limited size of the sample baskets used, it may be necessary to remove larger particles from

the sample (e.g. fraction > 20 mm)
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EN 15188:2020 (E)
6 Procedure
6.1 Experimental Procedure

The test basket shall be filled with the dust sample with the settled bulk density. Any surplus dust from

the upper margin has to be removed. It shall be checked by weighting if the settled bulk density is

reached with an accuracy of ± 2 %. Position the basket at the centre of the oven (see Figure 1) that has

been preheated to the test temperature.

NOTE It is also possible to position the basket at the centre of cold oven if the target oven temperature is

reached and is stable within 30 min.

The thermocouple for measuring the sample temperature is to be positioned with its hot junction

directly at the centre of the sample. The hot junctions of two additional thermocouples on opposite

sides will be freely installed in the air space at a distance of 5 cm to the sample (see Figure 2). These

two thermocouples are used to measure the oven temperature, corresponding to, in critical cases, the

T . The temperatures of these three thermocouples shall be recorded continuously over time.

In cases where the sample ignites the oven temperature may increase due to the heat released by the

burning sample. To prevent misinterpretation the oven temperature shall be taken at the crossing point

(where the temperature of the sample first reaches, and is equal to, the oven temperature) for the

evaluation of the test.

The temperature difference of both thermocouples measuring the oven temperature shall not exceed

2 K. If a larger temperature difference is observed the adjustment of the thermocouples and, if

necessary, the spatial temperature differences around the sample shall be checked.

The air inlet and air outlet openings of the oven shall be left open during the test to enable fresh air to

enter and combustion gases to leave the oven. A sufficient number of hot storage tests – with a fresh

dust sample for each test – shall be carried out to determine the highest oven temperature at which no

ignition occurs, as well as the lowest oven temperature at which the dust sample showed an ignition for

each sample volume chosen. Normally the test can be stopped if the temperature in the sample falls (see

case B in Figure 3) or if a situation like case C in Figure 3 occurs. Striking features during testing (e.g.

production of gases, physical changes to the sample) and the mass loss from samples shall be written

down.

Figure 3 is an idealised one. In some cases, the type B curve is followed by a steep increase of sample

temperature after the temperature drop has occurred. Attention should be paid to the fact that this may

happen after significantly long periods of time. In such cases, such modified type B curves have to be

evaluated as type C ones. This situation may also occur with type A curves.
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EN 15188:2020 (E)
Key

ϑ temperature of surrounding environment (for tests this is the oven temperature): shown by dashed lines

t duration of the test
P inflection point

t induction time (for Curve C): delineated by lines with dashes and dots. Starts at the time the sample

temperature crosses the oven temperature (ϑC) and finishes at the inflection point

A hot storage test type A
B hot storage test type B
C hot storage test type C

Figure 3 — Idealised temperature courses over time in dust samples of the same volume at hot

storage temperatures ϑ to ϑ
A C
6.2 Evaluation of tests

Figure 3 shows idealised temperature curves over time in samples from three hot storage tests of the

same volume and the same dust, but at different oven temperatures. The dashed horizontal lines show

the oven temperatures (ϑ to ϑ ) of the respective hot storage tests (A, B and C) where sample

A C
temperatures are shown by thick continuous lines.

If one works at temperatures significantly lower than the T the sample temperature will

asymptotically approach the oven temperature (curve A).

Higher oven temperatures show noticeable reactions with oxygen in the body of dust. Then sample

temperatures temporarily will be higher than oven temperatures. This indicates the beginning of the

self-heating processes, without self-ignition of the sample (curve B).
A test is evaluated as having ignited if one of two criteria is fulfilled:

a) when the temperature-time-curve, measured at the centre of the sample, shows an inflection point

during the heating phase at a temperature above the oven temperature
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b) when the temperature at the centre of the sample rises at least 60 K above its oven temperature.

Curve B relates to an oven temperature ϑ , slightly below the T . At its maximum, the sample

temperature surpasses the oven temperature by an amount Δϑ (to be less than 60 K). Thereafter the

sample temperature decreases to oven temperature.

Curve C relates to the oven temperature ϑ , a value just above the T . Heat production in the sample

has now reached a point at which it continuously surpasses the heat loss (by heat conduction,

convection and radiation). Stationary conditions are no longer possible. After an induction time the

temperature of the sample raises rapidly, until self-ignition occurs.

The self-ignition temperature lies between the oven temperatures of curves B and C.

The selection of the hot storage temperatures for the decisive final two tests shall be made in such a

way that the oven temperatures of the test just producing ignition (curve C) and that of the test not

producing an ignition (curve B) differ by not more than 2 K. The decisive test not producing an ignition

shall be repeated. The T is the highest oven temperature at which a given volume of dust just did not

ignite.

Besides the temperature recordings, the time interval between the positioning of a sample in the oven

and the achieving of the storage temperature as well as the complete storage period should be recorded

for every test. Additionally, the time interval between reaching the storage temperature and the ignition

(i.e. induction time: case C), or the time from exceeding the storage temperature until the maximum

sample temperature has been reached (case B), should be recorded.

Different methods allow extrapolation of the laboratory test results to larger storage volumes, see

Annex A. Primary method is the evaluation based on the thermal explosion theory according to Frank-

Kamenetskii (A.2) or Thomas (A.3). These methods also allow derivation of reaction kinetic data of the

self-ignition process.
A simplified, empirical method is described in A.5 (Pseudo-Arrhenius plot).

The results of these tests are documented in a table, comparing sample volumes tested, the respective

T values, and induction times. Further, results are represented in graphs, such as Figure A.1 and

Figure A.3.
6.3 Calibration of thermocouples

The whole measuring chain (thermocouples, compensating cables, A/D-converter, data acquisition

system) shall be calibrated at intervals according to internal fixed rules.
At least annually a function test and if necessary an adjustment shall be done.
7 Test report
The test report shall include at least the following details:
a) reference to this document (EN 15188:2020);
b) name and address of the test institute which carried out the tests;
c) name and address of the client;
d) characterization of the sample:

1) sample description (including when known particle size distribution and moisture content);

2) name or chemical composition of the sample;
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EN 15188:2020 (E)
3) bulk density;
4) sample preparation (if done e.g. for comparison of different dusts);

e) any changes to the test equipment or test procedures specified in this standard, the reasons

...

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