interlaboratory test 2012-2013 on the method en 14522_2005

Interlaboratory test 2012-2013 on the method

EN 14522:2005 Determination of the auto igni-tion temperature of gases and vapours /

IEC 60079-20-1, part 7 Method of test for auto-ignition temperature

Short name: Interlaboratory test 2012/13 on the auto ignition temperature of liquids

Final Report

Dr. Peter Lth Dr. Elisabeth Brandes

Thomas Stolz

reported by BAM Federal Institute for Materials Research and Testing

and Physikalisch-Technische Bundesanstalt PTB

Berlin, Braunschweig 06.05.2014

Authors

Dr. Peter Lth Dr. Elisabeth Brandes Thomas Stolz

Imprint

Interlaboratory test 2012-2013 on the method EN 14522:2005 Determination of the auto ignition temperature of gases and vapours / IEC 60079-20-1, part 7 Method of test for auto-ignition temperature

Final Report

Publisher: BAM Bundesanstalt fr Materialforschung und -prfung Unter den Eichen 87 12205 Berlin Telefon: +49 30 8104-0 Telefax: +49 30 8112029 Internet: www.bam.de

Copyright 2014 by BAM Bundesanstalt fr Materialforschung und -prfung

ISBN 978-3-9816380-0-4

http:www.bam.de

Organisation Panel

BAM Federal Institute for Materials Research and Testing Department 2 "Chemical Safety Engineering"

Dr. Peter Lth

Unter den Eichen 87, D-12205 Berlin

Phone: +49 (0)30-81041201, Fax: +49 (0)30-81041207

Email: [email protected]

Physikalisch-Technische Bundesanstalt PTB Department 3.7 Fundamentals of Explosion Protection

Dr. Elisabeth Brandes, Thomas Stolz

Bundesallee 100, D-38116 Braunschweig

Phone: +49 (0)531-592-3710 /-3412, Fax: +49 (0)531-5923705

Email: [email protected]

with support of the

Center for quality assurance for testing of dangerous goods and hazardous sub-stances

Operation & Administration

BAM Federal Institute for Materials Research and Testing Dr. Peter Lth

Physikalisch-Technische Bundesanstalt PTB Dr. Elisabeth Brandes, Thomas Stolz

Statistical Design, Analysis and Evaluation



Report



mailto:[email protected]:[email protected]

Contents 1 Glossary ............................................................................................................................................. 1 2 Introduction ........................................................................................................................................ 5 3 Aim ..................................................................................................................................................... 5 4 Interlaboratory test sample ................................................................................................................ 7

4.1 Manufacturing and delivery of the interlaboratory test sample .................................................7 4.2 Homogeneity and stability of the interlaboratory test sample ...................................................7

5 Special interlaboratory test equipment and prerequisites ..................................................................8 5.1 Special PTB lid to determine the temperature gradient inside the 200 ml Erlenmeyer

flask ........................................................................................................................................... 8 5.2 Calibration of the temperature measuring device .....................................................................8

6 Procedure of the interlaboratory test..................................................................................................8 6.1 Organisation.............................................................................................................................. 8 6.2 Participating laboratories ...........................................................................................................9 6.3 Test method ............................................................................................................................ 10 6.4 Interlaboratory test series TS .................................................................................................. 10 6.5 Interlaboratory test instructions and laboratory data input ......................................................11 6.6 Time schedule ......................................................................................................................... 13

7 Evaluation ........................................................................................................................................ 14 7.1 Test results .............................................................................................................................. 14

7.1.1 Quantity of test results ..................................................................................................14 7.1.2 Data check (inspection upon receipt) ...........................................................................15 7.1.3 Significant deviations from the method EN 14522:2005 or the interlaboratory test

instruction......................................................................................................................16 7.1.3.1 No data from TS 1 and TS 2 ............................................................................17 7.1.3.2 Droplet volume for Acetone and n-Heptane ....................................................17 7.1.3.3 Improper silicon tube ........................................................................................18 7.1.3.4 Temperature gradient inside the 200 ml Erlenmeyer flask ..............................18 7.1.3.5 Calibration of the thermocouple for measuring the auto ignition

temperature ......................................................................................................18 7.1.3.6 Lowest ignition temperature measurement ......................................................18 7.1.3.7 Incorrect calculation of Ti .................................................................................19

7.1.4 Results of the lowest temperature of ignition of TS 1 ...................................................21 7.1.5 Conformity of the test results (MIN lowest temperature of ignition) according to

EN 14522:2005, Annex A, Verification / IEC 60079-20-1, part 7 .................................22 7.2 Precision parameters of EN 14522:2005 / IEC 60079-20-1, part 7 of considered labs .......24

7.2.1 Statistical method..........................................................................................................24 7.2.2 Data base and selection of considered labs from all labs reporting results from

TS 1 .............................................................................................................................. 24 7.2.2.1 Selection of the results of the MIN lowest temperature of ignition of

Acetone ............................................................................................................25 7.2.2.2 Selection of the results of the MIN lowest temperature of ignition of

n-Heptane ........................................................................................................27 7.2.2.3 Overview of considered labs regarding all substances (Acetone and

n-Heptane) .......................................................................................................29 7.2.3 Values for verification of the apparatus for Acetone and n-Heptane ............................30

7.2.3.1 Total robust mean value, reproducibility and repeatability of the verification values of the MIN lowest temperature of ignition for Acetone and n-Heptane .................................................................................................31

7.2.3.2 Measurement uncertainty of the lab and validity for other test

substances .......................................................................................................36 7.2.4 Temperature gradient inside the 200 ml Erlenmeyer flask ...........................................38

7.2.4.1 Total robust mean value and reproducibility of the temperature gradient inside the 200 ml Erlenmeyer flask ..................................................................38

7.3 Laboratory performance .......................................................................................................... 43 7.3.1 Statistical method..........................................................................................................43 7.3.2 Data base and assessed laboratories ..........................................................................43 7.3.3 Target values of Ti and precision data .........................................................................45 7.3.4 Total robust mean value, reproducibility, repeatability and z score of the auto

ignition temperature Ti for Acetone and n-Heptane and assessment of the laboratories ................................................................................................................... 46

7.4 Influencing (disturbing) factors ................................................................................................ 51 8 Summary and conclusions ............................................................................................................... 67

8.1 Performance of the method EN 14522:2005 / IEC 60079-20-1, part 7 ..................................67 8.1.1 Values for verification of the apparatus for Acetone and n-Heptane according to

method EN 14522, Annex A of method EN 14522:2005 / IEC 60079-20-1, part 7 ......68 8.1.2 Temperature gradient inside the 200 ml Erlenmeyer flask ...........................................68

8.2 Possible influencing (disturbing) factors .................................................................................70 8.3 Performance of the laboratories according to the determination of the auto ignition

temperature Ti .........................................................................................................................70 8.4 Recommendations for the participants of the interlaboratory test to improve the

execution of the method .......................................................................................................... 71 8.5 Recommendations to improve the execution of the method...................................................72

9 References ....................................................................................................................................... 73 10 Appendix .......................................................................................................................................... 74

10.1 Order and Registration form ...................................................................................................74 10.2 Diameter input form.................................................................................................................76 10.3 Interlaboratory test instruction ................................................................................................. 77 10.4 Laboratory data input form...................................................................................................... 80

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Glossary

1 Glossary

Interlaboratory test

Lab.-No. ................................................... number of the anonymised participant (laboratory) in this

interlaboratory test

Considered labs ........................................ laboratories which meet the criteria for reporting acceptable

values for the review of the verification values of EN

14522:2005, Annex A / IEC 60079-20-1, part 7 and for the

derivation of the (new) orientation value of the temperature

gradient inside the 200 ml Erlenmeyer flask ( section

7.2.2)

TS 1 .......................................................... interlaboratory test series 1 (obligatory) according to the

interlaboratory test instruction ( Appendix 10.3)

TS 2 .......................................................... interlaboratory test series 2 (additional, optional) according

to the interlaboratory test instruction ( Appendix 10.3)

Technical terms

AIT measuring point ................................. position of the measuring thermocouple T1 on the outer

surface of the test vessel (200 ml Erlenmeyer flask) for

measuring the temperature according to EN 14522:2005,

Annex B, figure B.1 / IEC 60079-20-1, part 7

Hot air oven .............................................. oven to heat up the test vessel according to EN 14522:2005,

section 4.2.3 / IEC 60079-20-1, part 7

Test vessel and support ........................... 200 ml Erlenmeyer flask and the support according to EN

14522:2005, section 4.2.2 and Annex B / IEC 60079-20-1,

part 7

Temperature gradient

Temperature gradient inside the oven ...... temperature gradient in the hot air oven determined in ac-

cordance with EN 14522:2005, section 4.2.3 / IEC 60079-

20-1, part 7 (without test vessel)

Temperature gradient inside the 200 ml

Erlenmeyer flask ....................................... temperature gradient determined in accordance with the

interlaboratory test instruction TS 1, section 1 (hot air oven

with test vessel, Appendix 10.3)

BAM / PTB 1


Ignition temperature

AIT ............................................................ general abbreviation of the auto ignition temperature

Ti ............................................................... abbreviation of the auto ignition temperature in the sense of

EN 14522:2005 / IEC 60079-20-1, part 7 (MIN lowest tem-

perature of ignition reduced by 1,5 % and rounded to the

next 1 K.)

Lowest temperature of ignition ................. measured lowest temperature of the test vessel - at which

an ignition occurred - of each trial according to EN

14522:2005, section 4.5.2.2 Method S. Step 2 to step 7 of

Method S shall be carried out at least three times. If the re-

sults obtained (step 7) scatter more than 2 %, carry out two

additional test series. Thus, maximum 5 trials (and 5 lowest

temperatures of ignition) are possible.

MIN lowest temperature of ignition........... minimum value of the lowest temperatures of ignition of the

3 or 5 trials measured by Method S of EN 14522:2005, sec-

tion 4.5.2.2 / IEC 60079-20-1, part 7

MINLTI ...................................................... abbreviation of the MIN lowest temperature of ignition

Verification value ...................................... value for the verification of the apparatus according to EN

14522:2005, Annex A / IEC 60079-20-1, section 7.7

Statistics

Coverage factor k ..................................... multiplier to estimate the (expanded) measurement uncer-

tainty U of a result y [5]. The value of the coverage factor k is

chosen on the basis of the level of confidence required of

the interval y U to y + U ( Table 1-1)

Table 1-1: Value of the coverage factor k that produces an interval having a level of confidence assuming a normal distribution (source [5])

Coverage factor k Level of confidence [%]

1 68,27

1,645 90

1,960 95

2 95,45

2,576 99

3 99,73

Repeatability standard deviation, sr.......... precision under repeatability conditions, i.e. same laboratory,

same operator and same apparatus

BAM / PTB 2


Reproducibility standard deviation, sR ...... precision under reproducibility conditions, i.e. different labor-

atories, different operators, different apparatuses

Robust reproducibility / repeatability

Standard deviation .................................... calculated by using the Q method as described in DIN

38402-45 (=ISO/TS 20612) where outlier examination is not

required

Total robust mean value ........................... robust mean value over different laboratories (e.g. all or

considered labs) calculated by applying the so-called Ham-

pel estimator according to DIN 38402-45 (=ISO/TS 20612)

where outlier examination is not required

Expanded uncertainty of mean ................. parameter, associated with the total robust mean value of an

interlaboratory test, that characterizes the dispersion of the

values that could reasonably be attributed to the mean.

The confidence limits are represented as mean +/- k umean (coverage factor k, Table 1-1).

umean means standard uncertainty of mean value and the fol-

lowing equation applies:

in case of sr>0: (with repetitions of the measurement (replicates)):

and

in case of sr=0: (without repetitions of the measurement (replicates)):

95 % confidence interval of the mean ...... range, where in 95 of 100 interlaboratory tests the total ro-

bust mean value will be as expected (range within the green

strip of the figures e.g. Figure 7-6 on page 33). The inter-

val has been calculated on the basis of the expanded uncer-

tainty of mean (k=2).

Expanded measurement uncertainty U .... parameter, associated with the result of a measurement,

that characterises the dispersion of the values that could

reasonably be attributed to the measurand. In this interla-

boratory test the formula U = k sR was applied [6], [7].

95 % tolerance interval ............................ range, where in 95 of 100 laboratory tests the laboratory test

result will be as expected (range between the curve of the

lower tolerance limit value and the curve of the upper toler-

ance limit value). The tolerance interval has been calculated

on the basis of the expanded measurement uncertainty U

(k=2). BAM / PTB 3


Lower/upper tolerance limit of the

95 % tolerance interval ............................. = robust mean value -/+ expanded measurement uncer-

tainty (k=2)

BAM / PTB 4

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Introduction

2 Introduction For the classification, safe handling and use of chemicals, special standardised test methods have

been developed and are used worldwide. Safety experts must be able to fully rely on the precise exe-

cution of the respective laboratory tests and assessments. In this context interlaboratory tests (round

robin tests, interlaboratory comparisons / intercomparisons) are a crucial element of both the further

development and improvement of the methods and of a laboratory's quality system. Participation in

interlaboratory tests is explicitly recommended by the standard ISO/IEC 17025 [3].

This document reports on the results of the interlaboratory test 2012-2013 on the test method EN

14522:2005 Determination of the auto ignition temperature of gases and vapours[1] / IEC 60079-20-

1, part 7 Method of test for auto-ignition temperature [2].

The auto ignition temperature is an important safety characteristic for explosion protection and preven-

tion. It is the basis for classifying substances and explosion protected equipment into temperature

classes. Because safety characteristic data are not a pure substance constant but a figure which de-

notes a special property of the substance, the determination methods are standardised. Currently EN

14522 and IEC 60079-20-1, part 7 are under revision with the aim to combine both to a standard ac-

cepted worldwide. An important part of the standard is the laboratorys verification of their apparatus

and procedure. To base this forthcoming standard on reliable and up-to-date verification data an in-

terlaboratory test appears as the method of choice. The verification data given in the recent issues of

the standards are based on comparison measurements which date back to a long time ago and did

not include automated apparatuses.

3 Aim The initial idea of this interlaboratory test was born by the CEN/TC 305 WG 1 - Test methods for de-

termining the flammability characteristics of substances - in order to assess the performance of the

method EN 14522:2005 / IEC 60079-20-1, part 7 and to improve the method. Thus this interlaboratory

test should not be a proficiency test of laboratories.

Improvement and modification of the method EN 14522 The improvement of the method was focused on checking of the values for the verification of the ap-

paratus (verification values) (MIN lowest temperature of ignition of Acetone and n-Heptane) according

to EN 14522:2005, Annex A / IEC 60079-20-1, section 7.7.

In addition the criteria / requirements of the temperature characteristics of the test apparatus ( sec-

tion 4.2.3 EN 14522:2005) should be reviewed.

According to the current version of EN 14522:2005 the ability of the test apparatus should be checked

by the temperature gradient in two positions inside the oven without the test vessel in position (200 ml

Erlenmeyer flask, section 4.2.3 EN 14522:2005). However, differences between the temperature

conditions inside the oven without the Erlenmeyer flask and inside the Erlenmeyer flask may be possi-

ble. Thus the ability of the test apparatus (oven with Erlenmeyer flask) cannot be accurately checked

by the criteria of the temperature gradient inside the test oven without the Erlenmeyer flask.

BAM / PTB 5

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Aim

The organisation panel of this interlaboratory test therefore saw the necessity of an improvement of

the method by implementing a more appropriate criterion to assess the ability of the test apparatus. As

new approach it was suggested to generate orientation values of the temperature gradient inside the

200 ml Erlenmeyer flask mounted in the heated oven instead of the temperature gradient inside the

heated oven without a flask. For this purpose the temperature gradient inside the 200 ml Erlenmeyer

flask mounted in the heated oven should be determined by each participant of this interlaboratory test

( section 6.5 Interlaboratory test instruction).

Summary of the aims of this interlaboratory test 2012-2013 The aims of this interlaboratory test 2012-2013 on method EN 14522:2005 Determination of the auto

ignition temperature of gases and vapours / IEC 60079-20-1, part 7 Method of test for auto-ignition

temperature are:

Assessment of method EN 14522:2005 / IEC 60079-20-1, part 7 by the investigation of two in-

terlaboratory test samples in different laboratories by two series of the interlaboratory test

(TS 1 with a new 200 ml Erlenmeyer flask from BAM and TS 2 with a 200 ml Erlenmeyer flask

from the respective laboratory, Table 6-3) on the basis of the:

o recalculation of the values for the verification of the apparatus (verification values)

(MIN lowest temperature of ignition of Acetone and n-Heptane) according to EN

14522:2005, Annex A / IEC 60079-20-1, section 7.7

o derivation of orientation values of the temperature gradient inside the 200 ml Erlen-

meyer flask mounted in the heated oven in two positions (2,5 cm and 6 cm above the

bottom of the flask)

Assessment of laboratory performance on the basis of the determined auto ignition tempera-

tures Ti and formulation of recommendations for the participants of the interlaboratory test to

improve the execution of the method EN 14522:2005 / IEC 60079-20-1, part 7

Assessment of laboratory specific influence (disturbing) factors which may possibly have an

influence on the test result (Ti) of method EN 14522:2005 / IEC 60079-20-1, part 7.

BAM / PTB 6

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Interlaboratory test sample

4 Interlaboratory test sample The liquid interlaboratory test samples (Acetone and n-Heptane, Table 4-1) were chosen because

they are the verification substances in the recent edition of EN 14522:2005, Annex 1, Table A.1, / IEC

60079-20-1, part 7 [1], [2].

4.1 Manufacturing and delivery of the interlaboratory test sample

In January 2013 the interlaboratory test samples were prepared by BAM by decanting Acetone and n-

Heptane ( Table 4-1) from bottles of the supplier (each substance delivered from the supplier in

December 2102 in five 2.5 L bottles from one batch) into 250 ml borosilicate glass bottles to be deliv-

ered to the participating laboratories.

Table 4-1: Interlaboratory test samples Interlaboratory test samples

Substance and characteristics Quantity

A and B Acetone, 99,9 %, PESTINORM for pesticide resi-due analysis, MERCK 83656.320,

Supplier: VWR international,

VWR product code 83656.320,

Batch: 12Z4521, Spec. guaranteed until: 10.2015

approx. 250 ml of each

sample in a 250 ml borosil-

icate glass bottle

C and D n-Heptane, > 99.5%, puriss. p.a., AnalaR NOR-MAPUR, SIGMA/ALDRICH SIAL 51745-2.5L,

Supplier: VWR international,

VWR product: 24551.324,

Batch: 12H090509, Spec. guaranteed until: 08.2017, packaged under nitrogen

approx. 250 ml of each

sample in a 250 ml borosil-

icate glass bottle

The interlaboratory test samples A, B, C and D (four 250 ml bottles) together with the interlaboratory

test instruction, the data input form (files on USB stick), two 200 ml Erlenmeyer flasks to perform the

interlaboratory test on the method EN 14522:2005 ( section 6.5 / interlaboratory instruction, 1st test

series) and a special PTB lid were packed into transport containers and sent to the participants of

the interlaboratory test by BAM.

4.2 Homogeneity and stability of the interlaboratory test sample

Based on experience with the liquid substances Acetone and n-Heptane and the test method to de-

termine the auto ignition temperature Ti the interlaboratory test samples are known to be sufficiently

homogeneous and stable within the laboratory measuring period of this interlaboratory test (January

2013 to January 2014). No further tests to control the homogeneity and stability were performed.

Conclusion: The interlaboratory test samples Acetone and n-Heptane can be considered as suffi-ciently homogenous and stable for this interlaboratory test.

BAM / PTB 7

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Special interlaboratory test equipment and prerequisites

5 Special interlaboratory test equipment and prerequisites

5.1 Special PTB lid to determine the temperature gradient inside the 200 ml Erlenmeyer flask

Within the scope of this interlaboratory test the temperature gradient inside the heated 200 ml Erlen-

meyer flask should be determined. To avoid influences of uncontrolled air flows these measurements

have to be carried out with the Erlenmeyer flask closed by a well-fitting lid (special PTB lid) with a

hole for the thermocouple. This special PTB lid was manufactured by PTB with regard to the individ-

ual needs of the laboratories. For this purpose the participants were asked to determine the thickness

and diameter of the opening of the test vessel support ( Annex 10.1 and Appendix 10.2) to get a

really suitable special PTB lid.

The individual special PTB lid together with the interlaboratory test samples ( section 4.1) was

distributed to the labs by BAM.

5.2 Calibration of the temperature measuring device

The use of a calibrated temperature measuring device for measuring the AIT was a mandatory pre-

requisite for taking part in this interlaboratory test. For this purpose the participants were asked to

send information concerning the calibration of their temperature measuring devices ( Annex 10.1).

6 Procedure of the interlaboratory test

6.1 Organisation

The interlaboratory test was organised by BAM Federal Institute for Materials Research and Testing,

Berlin together with the PTB Physikalisch-Technische Bundesanstalt, Braunschweig within the context

of the interlaboratory test programme of the Center for Quality Assurance for Testing of Dangerous

Goods and Hazardous Substances.

BAM / PTB 8

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Procedure of the interlaboratory test

6.2 Participating laboratories

The interlaboratory test samples together with the test instruction and the laboratory data input form

( Appendix 10.1 and 10.4) were distributed to 15 participating labs ( Table 6-1).

Table 6-1: List of all 15 participating laboratories (14 laboratories submitted data from 16 testing apparatuses)

Laboratory / Agency Country

AkzoNobel Functional Chemicals B.V. The Netherlands

AQura GmbH Germany

Arkema Process And Product Safety Lab France

BAM Bundesanstalt fr Materialforschung und -prfung Germany

BASF SE Germany

Bayer Technology Services GmbH Germany

consilab Gesellschaft fr Anlagensicherheit mbH Germany

Dr. Krause GmbH Germany

F. Hoffmann-La Roche AG, Sicherheitslabor Switzerland

INERIS * France

Petrotest GmbH Germany

Physikalisch-Technische Bundesanstalt ** Germany

Siemens AG Germany

swissi Process Safety GmbH Switzerland

TNO Defence, Security and Safety The Netherlands

* ...... Participation with 2 different apparatuses: oven according to the IEC- and oven according to the EN-standard

** ..... Participation with 2 different apparatuses: automated apparatus and apparatus with visual observation

BAM / PTB 9


6.3 Test method

The interlaboratory test was based on method EN 14522:2005 Determination of the auto ignition

temperature of gases and vapours / IEC 60079-20-1, part 7 Method of test for auto-ignition tempera-

ture ( Table 6-2).

Table 6-2: Test method of the interlaboratory test

Test method Source

EN 14522:2005 Determination of the auto ignition temperature of gases and vapours

Beuth Verlag, Berlin [1]

IEC 60079-20-1, part 7 Method of test for auto-ignition temperature

International Electrotechnical Commission, Geneva [2]

EN 14522:2005 as well as IEC 60079-20-1, part 7 are designed to determine the auto ignition temper-

ature Ti of a flammable gas or vapour in mixture with air or air/inert gas, at ambient pressure up to 650

C. They are not suitable for describing interactions of hot surfaces with explosives.

The auto ignition temperature Ti is the lowest temperature (of a hot surface) at which under specified

test conditions, an ignition of a flammable gas or flammable vapour in mixture with air or air/inert gas

occurs. [1]

6.4 Interlaboratory test series TS

Within this interlaboratory test two test series ( Table 6-3) should be performed on two interlaborato-

ry test samples (Acetone and n-Heptane).

Test series 1 (TS 1) was obligatory for all participating labs.

Test series 2 (TS 2) was optional for the labs.

Table 6-3: Interlaboratory test series TS

Test series Special measures Remark

TS 1

Determination of the temperature gradient inside the 200 ml Erlenmeyer flask at 200 C and 500 C

Determination of the weight of the droplet Determination of the auto ignition temperature Ti with a

new 200 ml Erlenmeyer flask which BAM sent to the labs for determining the Ti

Obligatory for all labs

TS 2

Determination of the Ti under the conditions of TS 1 but with the 200 ml Erlenmeyer flask which was used typi-cally / normally in the past in the respective laboratory (instead of the new 200 ml Erlenmeyer flask of TS 1)

Additional, optional for the labs

BAM / PTB 10


6.5 Interlaboratory test instructions and laboratory data input

The test instruction of the interlaboratory test ( Appendix 10.3) which was distributed together with

the test samples included the following information:

1st Test series (obligatory)

1. Determination of the temperature gradient inside the 200 ml Erlenmeyer flask at 200 C and 500 C: 1.1. The oven shall be equipped with a 200 ml Erlenmeyer flask from the sample set. 1.2. Use the hole of the special PTB lid (which we have sent to you in the sample set) for a

thermocouple to determine the temperature gradient. 1.3. Mark this thermocouple (using e.g. a marker) so that it is possible to measure the tempera-

ture inside the Erlenmeyer flask at: the height of the AIT measuring point 6,0 cm from the bottom of the Erlenmeyer flask 9,0 cm from the bottom of the Erlenmeyer flask

1.4. Mount this thermocouple to determine the temperature gradient in the lid so that the temper-ature inside the Erlenmeyer flask is measured along the central vertical axis.

1.5. Close the opening of the 200 ml Erlenmeyer flask / upper part of lid with the special PTB lid equipped with the thermocouple. The lid is loose fitting.

1.6. Adjust the oven temperature to 200 C 5 C and 500 C 5C, resp. read at the AIT measuring thermocouple in its measuring position. Please start with 200 C 5 C.

1.7. Wait for temperature equilibrium ( T/ 2 min < 1 K). 1.8. Read the temperature at the thermocouple to determine the temperature gradient at:

9,0 cm from the bottom of the Erlenmeyer flask 6,0 cm from the bottom of the Erlenmeyer flask the height of the AIT measuring point

It is recommended to start the measurements at the height of 9 cm.

2. Determination of the weight of the droplet 2.1. Fill your metering device (e.g. pump, pipette, syringe) with the test substance (Acetone / n-

Heptane). 2.2. Determine the weight of 10 droplets of each substance in triplicate (3 values) with the aid of

a balance (precision 0,001 g).

BAM / PTB 11


3. Determination of the auto ignition temperature 3.1. Use a new 200 ml Erlenmeyer flask which we have sent to the lab for determining the AIT.

Use one new flask for Acetone and the other new flask for n-Heptane. 3.2. The tests should always be performed by one and the same laboratory assistant, otherwise

this should be noted. 3.3. The sample shall be tested as delivered (no special treatment is necessary like mixing etc.). 3.4. The sample shall be stored in the flask which you have received from BAM over the whole

testing period. The container shall be kept closed during storage. 3.5. It is mandatory to use only calibrated temperature measuring device(s) for measuring the ig-

nition temperature (e.g. calibrated measuring chain for AIT). 3.6. The AIT should be determined by the principles of EN 14522:2005, section 4.5.2.2 method S

or IEC 60079-20-1, section 7.3 3.7. Start the test series at the following temperatures (see Table 6-4):

Table 6-4: Starting temperature

Substance Starting temperature [C]

Acetone 560

n-Heptane 240

3.8. Record the ambient pressure before starting the measurements. 3.9. Perform the test for each sample (2 samples of Acetone and 2 samples of n-Heptane) as in-

dicated in EN 14522, section 4.5.2.2 or IEC 60079-20-1, section 7.3 with repetition. If possible, perform the determination of the AIT of one sample within one working day, other-wise it shall be noted.

3.10. For statistical purposes it is necessary to perform the tests in the following sequence (order): 1. Test sample A: Trial 1-3 (and 4-5 if necessary) 2. Test sample B: Trial 1-3 (and 4-5 if necessary) 3. Test sample C: Trial 1-3 (and 4-5 if necessary) 4. Test sample D: Trial 1-3 (and 4-5 if necessary) 5. Test sample A (repetition): Trial 1-3 (and 4-5 if necessary) 6. Test sample B (repetition): Trial 1-3 (and 4-5 if necessary) 7. Test sample C (repetition): Trial 1-3 (and 4-5 if necessary) 8. Test sample D (repetition): Trial 1-3 (and 4-5 if necessary)

3.11. All the other procedures as prescribed in EN 14522:2005 / IEC 60079-20-1, part 7 should be applied as usual in the respective laboratory.

2nd Test series (additional, optional)

We additionally asked the labs to perform a secondary test series (optional) using the following pro-cedure: 1. Use the 200 ml Erlenmeyer flask which used typically / normally in the past in the respective la-

boratory (instead of the new 200 ml Erlenmeyer flask, see above in point 3.1 of the 1st test series). This should be a used one in case the internal laboratory procedure does not prescribe to change the flask for each new AIT determination.

2. The other procedures in the 2nd test series should be performed under the same conditions as stipulated in point 3.2 - 3.11 of the 1st test series (see above).

Apart from this, the other details of the procedure were supposed to be applied as usual in the labora-

tory and in accordance with EN 14522:2005 Determination of the auto ignition temperature of gases

and vapours / IEC 60079-20-1, part 7 Method of test for auto-ignition temperature.

Laboratory specific parameters and test conditions were recorded with the laboratory data input form

( Appendix 10.4).

BAM / PTB 12


6.6 Time schedule

The following Table 6-5 shows the time schedule of the study.

Table 6-5: Time schedule of the interlaboratory test

Interlaboratory test procedure Time period

Conceptual design April 2012 to December 2012

Pre-announcement September 2012

Public announcement October 2012

Order and registration November 2012 to December 2012

Test sample preparation / distribution of the test sample and the test instruction December 2012 to January 2013

Laboratory measuring period January 2013 to April 2013 (January 2014)*

Final statistical evaluation January 2014 to February 2014**

Report and certificate May 2013 to May 2014 **

* ..... The laboratory measuring period was prolonged from April 2013 to 6th January 2014 because not all laboratories were able to perform the tests before 19th April 2013 (as originally arranged in January 2013).

** .... The statistical evaluation was postponed due to the prolonged testing period.

BAM / PTB 13

Interlaboratory test 2012-2013 on method EN 14522:2005 / IEC 60079-20-1, part 7 Evaluation

7 Evaluation

7.1 Test results

7.1.1 Quantity of test results

Seventeen participants (i.e. 15 different laboratories / agencies with a total of 17 test apparatuses

(oven)) were registered for this interlaboratory test in December 2012. One of these 17 participants

(Lab.-no 34) did not submit its test results (neither from TS 1 nor from TS 2).

The following Table 7-1 shows an overview of the submitted results from the participating labs.

Table 7-1: Results submitted from the labs (general overview)

Lab.-No.

Results submitted by labs in

Test series 1 (obligatory)

Test series 2 (additional, optional)

Sample A(Acetone)

Sample B(Acetone)

Sample C(n-Heptane)

Sample D(n-Heptane)

Sample A(Acetone)

Sample B(Acetone)

Sample C(n-Heptane)

Sample D(n-Heptane)

27 - - - - +* +* +* +*

34 - - - - - - - -

70 + + + + - - - -

106 + + + + - - - -

154 + + + + - - -

201 + + + + - - - -

233** + + + + - - - -

234** + + + + - - - -

248 + + + + + + + +

250 + + + + - +* - +*

251 + + + + - - - -

282 + + + + - - - -

472 + + + + + + + +

840 + + + + - - - -

908 + + + +* - - - -

961*** + + + + - - - -

962*** + + + + - - - -

- no data submitted + data submitted, data completed (with repetition) +* data submitted but not completed (missing values or without repetition of the measurements (replication)) ** Lab.-No. 233 and 234 belong to the same agency which operates with two different test apparatuses (oven) *** Lab.-No. 961 and 962 belong to the same agency which operates with two different test apparatuses (oven)

Conclusion: Measurements of the obligatory TS 1 were conducted by 15 participants. This quantity of test results of the obligatory TS 1 can be assumed as reliable for the statistical evaluation. However

the quantity of participating labs in TS 2 is very low and the quantity of results is insufficient for a relia-

ble statistical evaluation. In the case of lab 27 the results of Ti of TS 2 were used for the assessment

of the laboratory performance ( 7.2.4).

BAM / PTB 14


7.1.2 Data check (inspection upon receipt)

The following was checked upon receipt of the data:

Completeness of the data o e.g. missing data

Conformity, check of irregular deviations from o the testing method EN 14522:2005 / IEC 60079-20-1, part 7

o the interlaboratory test instruction

Plausibility, check of obvious incorrectness of the values of the submitted data o e.g. distorted data

Consistency, check of real incorrectness of the values in the submitted data input form by means of the additionally submitted raw data

o e.g. check of the Ti measurements against the original temperature.

Independent and stepwise data check The data check was performed directly after having received the data from the laboratory and before

starting the statistical analysis by different experts independently of one another:

First phase of data check by Elisabeth Brandes (PTB) and Peter Lth (BAM) directly after the submission of the data

from the labs

Second. phase of data check by Elisabeth Brandes (PTB) and Peter Lth (BAM) directly before starting the statistical analy-

sis.

Improving the data quality If possible, faulty data were corrected after consultation and by mutual agreement with the respective

laboratory. In case of missing data the labs were asked to complete their data.

BAM / PTB 15


16 BAM / PTB

7.1.3 Significant deviations from the method EN 14522:2005 or the interlaboratory test in-struction

Individual laboratory deviations from the requirements of the method EN 14522:2005 / IEC 60079-20-

1, part 7 and the interlaboratory test instruction, which may result in an incorrect statistical evaluation

and thus in incorrect conclusions, are shown in Table 7-2.

Table 7-2: Result of the data check significant deviations from the method EN 14522:2005 / IEC 60079-20-1, part 7 / interlaboratory test instruction 0 + green field = no deviation, 1+ red field = deviation, white field = no data (Note: The lab-no was not specified and the ranking of the column was changed for the sake of anonymity.)

Conclusion: Significant deviations from the requirements of the method EN 14522:2005 and / or the interlaboratory test instructions, which may result in an incorrect statistical evaluation and thus in in-

correct conclusions, were identified. These deviations are considered for the following statistical eval-

uation. The checked test results can be assessed as a sufficient basis for the statistical evaluation and

for reliable conclusions.

x x x x x x x x x x x x x x x x x

NodatafromTS1andTS2 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0

Nocorrectdropletvolumefor:Acetone 8

0 1 1 1 0 0 1 0 1 0 0 1 0 1 1 0

nHeptane 9 0 1 1 1 1 0 1 0 1 0 0 1 0 1 1 0

Impropersilicontube(DuetoreactionofAcetonewiththetubewhitesiliconprecipitatewasobservedontheflasksurface.) 1

0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0

Incorrecttemperaturegradientintheflaskdueto:missingvalues(valuesweresubmittedafterrequesting)

1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0

incorrectthermocouple(valueswerecorrectedafterrequesting) 1

0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0

NocalibrationofthermocoupleT1formeasuringtheT i(neitherofthethermocouplenorofthemeasuringchain)

2 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0

Incorrectlowestignitiontemperaturemeasurements:5Kintervalinsteadof(21)Kinterval(valueswerecorrectedafterrequesting)

1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0

missingsinglevalues(valueswerecorrectedafterrequesting) 4

0 0 0 0 0 0 0 0 0 0 1 1 0 0 1 1

incorrectdecimals(valueswerecorrectedafterrequesting) 1

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

norepetitionfornHeptaneatTS1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0

nomeasurementsfromtheobligatoryTS1 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0

missing2ndadditionaltrial(insummary5valuesarerequired) 1

0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0

IncorrectcalculationofT i(without1,5%reducing)(partialvalueswerecorrectedafterrequesting)

7 1 0 0 0 0 0 1 0 1 1 1 1 0 0 0 1

2 4 2 1 6 1 0 3 0 4 2 2 4 0 2 4 2Sum

LabNo.Parameter Sum


BAM / PTB 17

The following significant deviations have been observed.

7.1.3.1 No data from TS 1 and TS 2 One lab did not submit data during the laboratory measuring period.

7.1.3.2 Droplet volume for Acetone and n-Heptane EN 14522:2005, section 4.2.4 requires a metering device (e.g. pump, pipette, syringe) designed in

such a way that it is possible to meter droplets having a volume of 25 l 10 l. In eight labs the drop-

let volume for Acetone deviates from the required volume. In nine labs the droplet volume for n-

Heptane deviates from the required volume ( Table 7-3 and Figure 7-1).

Table 7-3: Mean volume of 1 droplet [l] for Acetone and n Heptane (green area = droplet volume conform to EN 14522:2005, section 4.2.4)

Acetone n-Heptane27 6,8 6,470 9,9 11,3

106 23,3 22,8154 23,5 23,3201 24,0 25,3233 23,5 17,2234 14,4 14,4248 24,2 22,5250 12,6 11,8251 11,1 12,1282 10,8 10,8472 10,9 12,3840 21,9 20,7908 8,1 10,4961 28,4 30,8962 30,7 36,7

Mean volume of 1 droplet [l] for sample

Lab.-No.


18 BAM / PTB

Figure 7-1: Mean volume of 1 droplet green area: target volume range according to EN 14522:2005, section 4.2.4 bold green line: target volume according to EN 14522:2005, section 4.2.4

7.1.3.3 Improper silicon tube One lab gave information about a white silicon precipitate which was observed on the flask surface. A

reaction of the silicone tube with Acetone was assumed by the lab.

7.1.3.4 Temperature gradient inside the 200 ml Erlenmeyer flask The instruction of TS 1 ( Appendix 10.3) asks to determine the temperature gradient.

One lab did not submit the effective temperatures at the AIT measuring point as required in the data

input form ( Appendix 10.4.). On request the lab has sent mean values of the effective temperatures.

One lab submitted incorrect values of the temperature inside the 200 ml Erlenmeyer flask due to a

wrong thermocouple type. The values were corrected by the lab by repeating the measurements after

replacing the wrong thermocouple type with the required correct type.

7.1.3.5 Calibration of the thermocouple for measuring the auto ignition temperature Two labs did not calibrate the thermocouple for determining the auto ignition temperature (neither the

thermocouple nor the measuring chain).

7.1.3.6 Lowest ignition temperature measurement 5 K interval instead of (2 1) K interval: In EN 14522:2005, section 4.5.2.2, step 4 it is required to lower the temperature of the test vessel in

intervals of (2 1) K. In one lab the investigations were performed in intervals of (5 1) K instead of

the in required intervals of (2 1) K. The values were corrected by the lab by repeating the tests.

0

5

10

15

20

25

30

35

40

27 70 106 154 201 233 234 248 250 251 282 472 840 908 961 962

Mea

n vo

lum

e of

1 d

ropl

et [

l]

Lab.No.

Acetone n-Heptane


BAM / PTB 19

Missing single values: Four labs did not submit all required single values.

Incorrect decimals: The decimals were prescribed in the data input form. One lab submitted values with incorrect deci-

mals. The values were corrected by the lab.

No repetition for n-Heptane at TS 1 One lab did not submit values for the repetition for the samples C and D (n-Heptane) in TS 1.

No values from the obligatory TS 1 One lab submitted measurements only from the additional, optional TS 2 but not from the obligatory

TS 1.

Missing 2nd additional trial In the method EN 14522:2005, section 4.6 stipulates carring out two additional trials if the results ob-

tained (step 7) scatter more than 2 %. One lab performed only one additional trial instead of two.

7.1.3.7 Incorrect calculation of Ti To obtain the auto ignition temperature Ti EN 14522:2005, section 4.5.2.2 states reducing the lowest

value of the lowest temperatures of ignition by the absolute deviation calculated using the reproducibil-

ity value (1,5 % rel.) and rounding this value to the next 1 K. Seven labs did not perform this calcula-

tion before submitting the results.

The individual Ti calculation procedure of the lab was checked by the statistical operator. Differences

are shown in Table 7-4 and Table 7-5.


20 BAM / PTB

Table 7-4: Difference between Ti from the lab and Ti recalculated by the statistical operator for Ace-tone in TS 1 [C] (green fields = calculation conform to EN 14522:2005 /, section 4.5.2.2)

Table 7-5: Difference between Ti from the lab and Ti recalculated by the statistical operator for n-Heptane in TS 1 [C] (green fields = conform to EN 14522:2005, section 4.5.2.2)

Conclusion: Differences between Ti from the lab and Ti recalculated by the statistical operator were identified. The reason for the differences is a improper calculation and / or rounding by the laboratory

assistants. Therefore, these deviations must be taken into account in the following statistical analysis.

Sample C Sample D Sample C (repetition)

Sample D (repetition)

2770 1 0 0 1

106 0 0 0 0154 2 2 1 0201 0 0 0 0233 1 0 1 0234 0 0 0 0248 0 0 0 0250 0 0 1 0251 1 0 0 0282 0 0 0 0472 1 1 0 0840 1 1 1 1908 1 0 0 0961 1 0 0 0962 0 0 0 0

n-HeptaneDifference between Ti from the lab and Ti recalculated

Lab.-No.



2770 1 0 0 1

106 0 0 0 0154 2 2 1 0201 0 0 0 0233 1 0 1 0234 0 0 0 0248 0 0 0 0250 0 0 1 0251 1 0 0 0282 0 0 0 0472 1 1 0 0840 1 1 1 1908 1 0 0 0961 1 0 0 0962 0 0 0 0

n-HeptaneDifference between Ti from the lab and Ti recalculated

Lab.-No.


BAM / PTB 21

7.1.4 Results of the lowest temperature of ignition of TS 1

The checked laboratory results ( section 7.1.2 and section 7.1.3) of the lowest temperature of igni-

tion are shown in Table 7-6 and Table 7-7.

Table 7-6: Lowest temperature of ignition [C] of the samples A and B (both Acetone) of TS 1 (conditional formatted table: red areas = comparatively high values, blue areas = comparatively low values)

Table 7-7: Lowest temperature of ignition [C] of the samples C and D (both n-Heptane) of TS 1

(conditional formatted table: red areas = comparatively high values, blue areas = comparatively low values)

Lab.-No.

Trial: 1 2 3 A1 A2 1 2 3 A1 A2 1 2 3 A1 A2 1 2 3 A1 A22770 541,0 541,0 541,1 528,6 527,3 533,7 534,4 531,8 534,2 529,4 531,1 528,1

106 536,0 537,0 538,0 540,0 533,0 539,0 532,0 538,0 539,0 531,0 536,0 534,0154 557,1 559,3 559,1 560,7 560,6 561,6 554,1 554,9 555,5 555,7 557,0 554,9201 536,0 530,0 528,0 536,0 530,0 530,0 529,0 528,0 530,0 531,0 531,0 530,0233 526,0 528,3 525,3 517,3 526,4 525,6 523,5 525,4 527,2 526,7 526,9 524,7234 525,0 528,1 528,1 527,5 527,9 528,0 523,7 529,6 530,9 520,2 519,4 518,1248 533,3 535,4 535,1 536,3 533,5 535,4 533,4 535,2 535,3 533,0 535,3 533,2250 543,0 540,0 544,1 538,0 541,5 542,0 530,3 532,8 534,6 534,6 533,6 532,4251 527,0 521,0 530,0 520,0 520,0 520,0 525,0 524,0 525,0 525,0 523,0 521,0282 544,0 548,0 546,0 547,0 545,0 546,0 561,0 559,0 559,0 567,1 551,0 553,0 551,0 551,0472 565,5 566,0 564,2 559,2 562,7 561,0 564,0 561,0 555,7 560,9 561,0 550,5 550,8840 531,5 531,5 531,5 534,5 536,5 534,5 536,6 536,6 534,5 536,6 536,6 539,6908 519,8 520,0 519,8 521,2 521,2 515,0 519,4 521,1 529,6 527,8 521,7 530,1961 531,9 531,8 532,3 530,5 529,5 528,7 529,4 529,6 527,3 526,3 526,8 527,0962 517,0 521,6 520,5 520,0 522,0 519,9 521,1 519,4 515,5 521,0 517,7 521,6

AcetoneLowesttemperatureofignition[C]

SampleA SampleB SampleA(repetiton)

SampleB(repetition)

Lab.-No.

Trial: 1 2 3 A1 A2 1 2 3 A1 A2 1 2 3 A1 A2 1 2 3 A1 A22770 223,8 223,7 221,9 220,7 224,0 227,3 221,9 221,9 223,7 221,6 222,8 220,7

106 222,0 222,0 218,0 222,0 222,0 223,0 219,0 226,0 222,0 220,0 222,0 224,0154 240,2 240,1 237,0 237,1 237,2 237,4 235,0 237,4 233,6 239,6 242,1 238,0201 220,0 225,0 220,0 222,0 221,0 223,0 221,0 221,0 220,0 220,0 220,0 223,0233 222,0 224,5 221,3 222,2 220,0 220,5 219,1 219,2 218,8 231,6 234,7 236,7234 214,9 216,1 216,0 218,3 216,7 215,2 216,6 214,1 214,5 215,2 215,3 215,3248 222,5 222,1 222,5 221,5 221,1 220,0 223,3 223,5 223,5 221,2 223,0 223,3250 220,5 220,9 219,4 219,7 220,5 221,4 218,1 217,2 217,5 216,5 217,3 219,5251 232,0 232,0 232,0 218,0 219,0 219,0 230,0 230,0 230,0 220,0 229,0 228,0282 239,6 241,6 239,6 245,6 243,6 238,6 238,6 239,6 239,6 239,6 237,6 238,6 239,6 239,6472 225,6 221,1 221,2 219,9 220,4 219,5 218,6 219,0 219,3 220,4 219,9 220,4840 224,1 224,1 224,1 224,1 222,1 224,1 224,1 224,1 224,1 222,1 222,1 224,1908 218,7 219,1 219,1 219,3 219,7 219,9961 219,8 221,3 220,8 222,7 219,6 221,8 219,8 221,5 217,5 218,7 218,8 220,9962 225,9 224,0 222,2 220,9 220,2 220,1 220,2 219,4 216,8 219,4 219,6 223,8

nHeptaneLowesttemperatureofignition[C]

SampleC SampleD SampleC(repetiton)

SampleD(repetition)


22 BAM / PTB

7.1.5 Conformity of the test results (MIN lowest temperature of ignition) according to EN 14522:2005, Annex A, Verification / IEC 60079-20-1, part 7

According to EN 14522:2005, Annex A a verification of the existing apparatus at the lab is required.

Verification will be confirmed if the values obtained for the MIN lowest temperature for ignition (not

corrected as described in 4.6.2.of EN 14522:2005) do not deviate more than 1,5 % from the values

given in Table A.1. The respective verification ranges for Acetone and n-Heptane are listed in Table

7-8.

Table 7-8: Values* for verification of the apparatus according to EN 14522:2005, Annex A, Table A.1 /

IEC 60079-20-1, part 7

Substance Measured MIN lowest temperature of ignition [C]

Verification range [C] (1,5 %)

Acetone 535* 527,0 543,0

n-Heptane 221* 217,7 224,3

* .... The values given are not corrected as described in section 4.6.1. of EN 14522:2005. The values given in Table A.1 are the respective mean values of the MIN lowest temperatures reached by former interlaboratory tests using method S of EN 14522:2005, section 4.5.2).

According to EN 14522:2005, Annex A / IEC 60079-20-1, part 7 existing apparatuses shall be checked

at least every 12 months or whenever parts of the apparatus, except the flask, have been changed or

renewed. Using this interlaboratory test the current results of verification of the participants are shown

in Table 7-9 and Table 7-10.


BAM / PTB 23

Table 7-9: MIN lowest temperature of ignition* [C] of the lab for the samples A and B (both Acetone) in TS 1, conditional formatted table according to the verification data of EN 14522:2005, Annex A / IEC 60079-20-1, part 7: green areas = values are within the verification range of Acetone orange areas = values outside the verification range of Acetone

*. The values are not corrected as described in section 4.6.2.of EN 14522:2005.

Table 7-10: MIN lowest temperature of ignition* [C] of the lab for the samples C and D (both n-Heptane) in TS 1 conditional formatted table according to the verification data of EN 14522:2005, Annex A/ IEC 60079-20-1, part 7: green areas = values are within the verification range of n-Heptane orange areas = values outside the verification range of n-Heptane

*The values are not corrected as described in section 4.6.2.of EN 14522:2005.

Sample A Sample B Sample A (repetition)

Sample B (repetition)

2770 541,0 527,3 531,8 528,1

106 536,0 533,0 532,0 531,0154 557,1 560,6 554,1 554,9201 528,0 530,0 528,0 530,0233 525,3 517,3 523,5 524,7234 525,0 527,5 523,7 518,1248 533,3 533,5 533,4 533,0250 540,0 538,0 530,3 532,4251 521,0 520,0 524,0 521,0282 544,0 545,0 559,0 551,0472 564,2 559,2 555,7 550,5840 531,5 534,5 534,5 536,6908 519,8 515,0 519,4 521,7961 531,8 528,7 527,3 526,3962 517,0 519,9 515,5 517,7

Acetone - MIN lowest temperature of ignition of trial 1-5 in TS 1 [C]

Lab.-No.



2770 221,9 220,7 221,9 220,7

106 218,0 222,0 219,0 220,0154 237,0 237,1 233,6 238,0201 220,0 221,0 220,0 220,0233 221,3 220,0 218,8 231,6234 214,9 215,2 214,1 215,2248 222,1 220,0 223,3 221,2250 219,4 219,7 217,2 216,5251 232,0 218,0 230,0 220,0282 239,6 238,6 237,6 238,6472 221,1 219,5 218,6 219,9840 224,1 222,1 224,1 222,1908 218,7 219,3961 219,8 219,6 217,5 218,7962 222,2 220,1 216,8 219,4

Lab.-No. n-Heptane - MIN lowest temperature of igition of trial 1-5 in TS 1 [C]


24 BAM / PTB

Conclusion: Deviations from the requirements of the standardised test method and / or the interla-boratory test instructions, which may result in an incorrect statistical evaluation and thus in incorrect

conclusions, were identified. Therefore, these deviations must be taken into account in the following

statistical analysis. When considering these deviations the checked test results can be assessed as a

sufficient data basis for the statistical evaluation and for reliable conclusions.

7.2 Precision parameters of EN 14522:2005 / IEC 60079-20-1, part 7 of con-sidered labs

Precision parameters were calculated based on the analysis of:

the MIN lowest temperature of ignition of Acetone and n-Heptane ( section 7.2.3, recalcula-

tion of the verification values in the sense of method EN 14522:2005, Annex A / IEC 60079-

20-1, section 7.7) and

the temperature gradient inside the 200 ml Erlenmeyer flask mounted in the heated oven (

section 7.2.4, calculation of the (new) orientation value of the temperature gradient inside the

200 ml Erlenmeyer flask).

7.2.1 Statistical method

The method according to DIN 38402-45 (=ISO/TS 20612) was applied to calculate the mean across all

considered labs ( section 7.2.2) as well as the corresponding repeatability and reproducibility

standard deviations. This method is a robust method and no outlier examination is required.

The evaluation of the data was performed using the software package PROLab Plus 2014 [8], [9].

PROLab Plus is widely employed for the evaluation of interlaboratory tests and laboratory proficiency

tests.

7.2.2 Data base and selection of considered labs from all labs reporting results from TS 1

Due to the identified deviations ( section 7.1.3) it is necessary to check the results of TS 1 with re-

spect to their usability for the statistical analysis and for reliable conclusions. Only results from labora-

tories which are able to generate acceptable values of the MIN lowest temperature of ignition1 in the

sense of the EN 14522 should be considered. These labs are referred to in the following as consid-

ered labs.

Criteria for selection of labs reporting acceptable values (considered labs) The criteria for the selection of labs with acceptable values (considered labs) from all labs are:

Labs with values of the MIN lowest temperature of ignition which are not obviously outlier

values.

Labs with values of the MIN lowest temperature of ignition which belong to an accepted main

mode (main sub-group) concerning the Kernel density estimation.

(Note: In general, distributions with only one mode are called unimodal, while distributions 1 The results of Ti were not used as a criterion because of the calculation errors of several labs ( section 7.1.3.7).


BAM / PTB 25

with two or more modi are called bimodal or multimodal. Multimodal distributions indicate

that there might be two or more groups of participants with clearly differing results. However,

only a mode which is based on at least 25 % of the measurement values by one group of

labs should be considered as forming a sub-group.)

Labs with values of the MIN lowest temperature of ignition within the verification values of

EN 14522:2005, Annex A or not far from these verification values.

Labs with results not fulfilling these criteria must be assessed as not acceptable for the further statisti-

cal analysis and should be ignored. These labs are referred to in the following as unconsidered labs.

7.2.2.1 Selection of the results of the MIN lowest temperature of ignition of Acetone The distribution of the results of the MIN lowest temperature of ignition of Acetone of all labs of TS 1 is

given in Figure 7-2.

Figure 7-2: Kernel density estimation for MIN lowest temperature of ignition of sample A and B (Acetone) in TS 1 of all labs green area: verification range for Acetone of EN 14522:2005, Annex A/ IEC 60079-20-1, section 7.7 ( Ta-ble 7-8)

Figure 7-2 shows a bimodal distribution pattern of the MIN lowest temperature of ignition of the Ace-

tone samples. At least two sub-groups of labs can be identified. A small group of labs (approx. 20 % of

0,00

0,01

0,02

0,03

0,04

0,05

480 490 500 510 520 530 540 550 560 570 580 590 600

Prob

abilityden

sity

MINlowesttemperatureofignition[C]

KernelDensityPlot

AA(repetition)BB(repetition)MeanofA,B


26 BAM / PTB

all labs) has submitted a higher MIN lowest temperature of ignition than the main group of the labs

(approx. 80 % of all labs). The main mode group relating to distribution pattern can be assessed as

nearly a normal distribution of both the MIN temperature of ignition of the single test and the mean of

the MIN temperature of ignition (although not a perfect normal distribution). The interval of the main

mode MIN lowest temperature of ignition of Acetone ranges from approx. 510 C to approx. 545 C.

As demonstrated in Figure 7-2 the main mode interval covers the verification range for Acetone of EN

14522:2005, Annex A / IEC 60079-20-1, part 7 ( Table 7-8).

Conclusion: Figure 7-2 shows a bimodal distribution pattern of the MIN lowest temperature of ignition of the Acetone samples. The interval of main mode between approx. 510 C and approx. 545 C can

be assessed as sufficient for the selection of considered labs with acceptable results of the MIN low-

est temperature of ignition of the Acetone under the conditions and instructions of this interlaboratory

test.

Figure 7-3 shows the results of the MIN lowest temperature of ignition of the Acetone samples A and

B and their repetition.

Figure 7-3: MIN lowest temperature of ignition values of Acetone of trial 1-5 in TS 1 of all labs green area: verification range for Acetone of EN 14522:2005, Annex A/ IEC 60079-20-1, section 7.7 ( Table 7-8) bold green line: verification temperature of EN 14522:2005, Annex A/ IEC 60079-20-1, section 7.7 ( Table 7-8)

With regard to the selection criteria ( section 7.2.2) the following laboratories do not meet the main

mode interval for Acetone from approx. 510 C to approx. 545 C.

Labs with results outside of this interval ( Figure 7-3) must be assessed as not acceptable and are

ignored as unconsidered labs:

Lab 154, Lab 282, Lab 472.

500505510515520525530535540545550555560565570

70 106 154 201 233 234 248 250 251 282 472 840 908 961 962

MIN

low

est t

empe

ratu

re o

f ign

ition

[C

]

Lab.-No.

Sample ASample BSample A (repetition)Sample B (repetition)Mean of MIN


BAM / PTB 27

Thus the Acetone results of these three labs have to be ignored for the further statistical evaluation to

determine the final precision data of EN 14522:2005 / IEC 60079-20-1, part 7.

The considered labs for Acetone are the following 12 labs:

Lab 070, Lab 106, Lab 201, Lab 233, Lab 234, Lab 248, Lab 250, Lab 251, Lab 840, Lab 908, Lab 961, Lab 962.

7.2.2.2 Selection of the results of the MIN lowest temperature of ignition of n-Heptane The distribution of the results of the MIN lowest temperature of ignition of n-Heptane of all labs of TS 1

is given in Figure 7-4.

Figure 7-4: Kernel density estimation for MIN lowest temperature of ignition of sample C and D (n-Heptane) in TS 1 of all labs green area: verification range for n-Heptane of EN 14522:2005, Annex A / IEC 60079-20-1, part 7 ( Ta-ble 7-8)

0,00

0,05

0,10

0,15

0,20

0,25

200 205 210 215 220 225 230 235 240 245 250

Prob

abilityden

sity

MINlowesttemperatureofignition[C]

KernelDensityPlot

CC(repetition)DD(repetition)MeanofC,D


28 BAM / PTB

Figure 7-4 shows a multimodal distribution pattern of the MIN lowest temperature of ignition of the n-

Heptane samples. At least two sub-groups of labs can be identified. A small group of labs (approx. 20

% of all labs) has submitted higher MIN lowest temperatures of ignition than the main group of the labs

(approx. 80 % of all labs). The distribution pattern main mode group can be assessed as nearly a

normal distribution of both the MIN temperature of ignition of the single test and the mean of the MIN

temperature of ignition (although not a perfect normal distribution). The interval of the main mode MIN

lowest temperature of ignition of n-Heptane ranges from approx. 214 C to approx. 228 C. As demon-

strated in Figure 7-4 the main mode interval covers the verification range for n-Heptane of EN

14522:2005, Annex A ( Table 7-8).

Conclusion: Figure 7-4 shows a multimodal distribution pattern of the MIN lowest temperature of ignition of the n-Heptane samples. The interval of main mode between approx. 214 C to approx.

228 C can be assessed as sufficient for the selection of considered labs with acceptable results of

the MIN lowest temperature of ignition of the n-Heptane under the conditions and instructions of this

interlaboratory test.

Figure 7-5 shows the results of the MIN lowest temperature of ignition of the n-Heptane samples A

and B and their repetition.

Figure 7-5: MIN lowest temperature of ignition values of n-Heptane of trial 1-5 in TS 1 green area: verification range for n-Heptane of EN 14522:2005, Annex A / IEC 60079-20-1, part 7 ( Ta-ble 7-8) bold green line: verification temperature of EN 14522:2005, Annex A / IEC 60079-20-1, part 7 ( Table 7-8)

210

215

220

225

230

235

240

245

70 106 154 201 233 234 248 250 251 282 472 840 908 961 962

MIN

low

est t

empe

ratu

re o

f ign

ition

[C

]

Lab.-No.

Sample C

Sample D

Sample C (repetition)


Mean of MIN


BAM / PTB 29

With regard to the selection criteria ( section 7.2.2) the following laboratories do not meet the main

mode interval for n-Heptane from approx. 214 C to approx. 228 C.

Labs with results outside ( Figure 7-5) of this interval must be assessed as not acceptable and

should be ignored as unconsidered labs:

Lab 154, Lab 282.

Thus the results of n-Heptane of these two labs cannot be considered at the further statistical evalua-

tion for determining the final precision data of EN 14522:2005 / IEC 60079-20-1, part 7.

The considered labs for n-Heptane are the following 13 labs:

Lab 070, Lab 106, Lab 201, Lab 233, Lab 234, Lab 248, Lab 250, Lab 251, Lab 472, Lab 840, Lab 908, Lab 961, Lab 962.

7.2.2.3 Overview of considered labs regarding all substances (Acetone and n-Heptane) Table 7-11 shows the considered labs which meet the criteria for the selection of labs with accepta-

ble values for the recalculation of the verification values of method EN 14522:2005, Annex A / IEC

60079-20-1, part 7) and for the derivation of the (new) orientation value of the temperature gradient

inside the 200 ml Erlenmeyer flask.


30 BAM / PTB

Table 7-11: Selected labs for the statistical evaluation yes = considered labs, no = not considered

Lab.-No. Selected labs for further statistical evaluation in dependence on interlaboratory test sample: Acetone n-Heptane

70 yes yes

106 yes yes

154 no no

201 yes yes

233** yes yes

234** yes yes

248 yes yes

250 yes yes

251 yes yes

282 no no

472 no yes

840 yes yes

908 yes yes

961*** yes yes

962*** yes yes

** Lab.-No. 233 and 234 belong to one (the same) agency which operates with two different test apparatuses (oven) *** Lab.-No. 961 and 962 belong to one (the same) agency which operates with two different test apparatuses (oven)

Conclusion: Not all data of all labs can be included in the statistical procedure to generate reliable precision data for the method. Nevertheless, the number of valid results from 12 considered labs for

Acetone and 13 considered labs for n-Heptane is sufficient to generate reliable precision indicators

and to recalculate the verification values for Acetone and n-Heptane of EN 14522:2005, Annex A / IEC

60079-20-1, part 7 and to derive the (new) orientation value of the temperature gradient inside the

200 ml Erlenmeyer flask.

7.2.3 Values for verification of the apparatus for Acetone and n-Heptane

The calculation of the precision parameters of the re-calculated values for verification of the apparatus

according to EN 14522:2005, Annex A / IEC 60079-20-1, section 7.7. was based on the results of the

mean of the MIN lowest temperature of ignition of TS 1 of the considered labs ( Table 7-11) of the

interlaboratory test samples Acetone and n-Heptane (purity and other characteristics of the samples

Table 4-1).

Important note: For the calculation of the above-mentioned precision parameters it is not mandatory that the requirements according to EN 14522:2005, Annex A / IEC 60079-20-1, part 7 (verification of

the apparatus by checking of Acetone and n-Heptane) are met. This is due to the intention to validate

and adjust verification values of Acetone and n-Heptane by this interlaboratory test.


BAM / PTB 31

7.2.3.1 Total robust mean value, reproducibility and repeatability of the verification values of the MIN lowest temperature of ignition for Acetone and n-Heptane

A summary of the obtained total robust mean values, reproducibility and repeatability standard devia-

tions ( section 7.2.1) of the interlaboratory samples Acetone and n-Heptane across the considered

labs are given in the following Table 7-12.

The expanded uncertainty of the mean (k=2, 95 % confidence interval of the total robust mean value)

and expanded measurement uncertainty (k=2) with the 95 % tolerance interval with the lower and

upper tolerance limits for the MIN lowest temperature of ignition of the interlaboratory samples Ace-

tone and n-Heptane according to EN 14522 / IEC 60079-20-1, part 7 are derived from the repeatability

standard deviation sr and the reproducibility standard deviation sR. These values are also given in Table 7-12.

Table 7-12: Precision parameters of the results of the MIN lowest temperature of ignition of the interla-

boratory samples Acetone and n-Heptane across the considered labs obtained by the in-terlaboratory test 2010 - 2011 on method EN 14522:2005 / IEC 60079-20-1, part 7

Precision parameter according to DIN 38402-45 ( section 7.2.1)

MIN lowest temperature of ignition of

Acetone n-Heptane

Number of involved laboratories (considered labs) 12 13

Rob

ust

Total robust mean value2 expanded uncertainty of mean (k=2)3 [C]

527,5 4,4

220,4 1,3

Repeatability s.d. sr [C] 2,4 1,2

Rel. repeatability s.d. rel. sr [%] 0,5 0,5

Reproducibility s.d. sR4 [C] 7,9 2,5

Rel. reproducibility s.d. rel. sR [%] 1,5 1,1

Expanded measurement uncertainty (k=2)5 [C] 15,8 5,0

Lower tolerance limit of the 95 % tolerance interval [C] 511,6 215,4

Upper tolerance limit of the 95 % tolerance interval [C] 543,3 225,4

2 The non rounded total robust mean values (527,467 C and 220,407 C respectively) of the MIN lowest temperature have been used as basis for calculating the target mean values of the auto ignition temperature Ti in section 7.3, Table 7-15. 3 The 95 % confidence intervals of the total robust mean value in Figure 7-6 and Figure 7-7 have been calculated on the basis of this expanded uncertainty of mean (k=2). 4 The non rounded sR values (7,919 C and 2,513 C) of the MIN lowest temperature of ignition have been used as the basis for calculating the target reproducibility standard deviations of the auto ignition temperature Ti in section 7.3, Table 7-15 5 Validity of the values of the expanded measurement uncertainty (k=2): section 7.2.3.2.


32 BAM / PTB

The results of the MIN lowest temperature of ignition for Acetone and n-Heptane of the considered

labs are shown in the following Figure 7-6 and Figure 7-7.

In these figures the blue boxes symbolise the laboratory's repeatability standard deviation sr of the MIN

lowest temperature of ignition for Acetone and n-Heptane. The larger the box, the higher the variability

of the results. The horizontal line in the middle of the blue boxes indicates the laboratory mean value,

while the blue diamonds indicate the individual MIN lowest temperature of ignition of TS 1 of the con-

sidered labs.

The figures include ( Glossary 1 and Table 7-12):

the total robust mean value ( section 1 Glossary) across the considered labs as a dark

blue horizontal line, together with the 95 % confidence interval of the total robust mean value

(green strip) ( section 1 Glossary)

the repeatability standard deviation sr (right yellow box)

the reproducibility standard deviation sR (left yellow box)

the lower and upper tolerance limits of the 95 % tolerance interval ( section 1 Glossary) for

the laboratory mean values (red lines).


BAM / PTB 33

Figure 7-6: Analysis for the MIN lowest temperature of ignition of Acetone of the considered labs, blue diamonds: single values of the MIN lowest temperature of ignition SR: reproducibility s.d., sR Sr: repeatability s.d., sr

Figure 7-7: Analysis for the MIN lowest temperature of ignition of n-Heptane of the considered labs, blue diamonds: single values of the MIN lowest temperature of ignition SR: reproducibility s.d., sR Sr: repeatability s.d., sr

PROLab Plus

Laboratory

962

908

251

233

234

961

201 70 106

248

840

250

C

542540538536534532530528526

524522520518516514512

Mean

SR

Sr

Sample: Acetone - MIN low est temperature of ignitionMeasurand: MIN low est temperature of ignitionMethod: DIN 38402 A45No. of laboratories: 12

Assigned value: 527,467 C (Empirical value)Rel. target s.d.: 1,50% (Empirical value)Rel. repeatability s.d.: 0,46%Range of tolerance: 511,629 - 543,305 C (|z-score|


34 BAM / PTB

The Youden plot of the laboratory mean of the MIN lowest temperature of ignition of Acetone and n-

Heptane of the considered labs of TS 1 is shown in Figure 7-8.

Figure 7-8: Youden plot of the laboratory mean of the MIN lowest temperature of ignition of Acetone

and n-Heptane of the considered labs The Youden plot demonstrates that all means of the MIN lowest temperature of ignition of Acetone

and n-Heptane of the considered labs are inside the 95 % confidence area (green market ellipse)

and no substantial systematic errors are incorporated in the techniques of the different labs.

Acetone - MIN low est temperature of ignition [C]560550540530520510500

n-H

epta

ne -

MIN

low

est t

empe

ratu

re o

f ign

ition

[C]

230,0

227,5

225,0

222,5

220,0

217,5

215,0

212,5

210,0

0,1 % level

1 % level

5 % level

70

106201

233

234

248

250

251

840

908 961962


BAM / PTB 35

The z scores of the laboratory mean of the MIN lowest temperature of ignition of Acetone and n-

Heptane of the considered labs of TS 1 are demonstrated in Figure 7-9. The z scores are explained

in detail in section 7.3. Summarised, a laboratorys result is:

satisfactory if ........... |z score| 2

questionable if ....... 2 < |z score| < 3

unsatisfactory if ....... |z score| 3.

Acetone n-Heptane

Figure 7-9: z scores of the laboratory mean of the MIN lowest temperature of ignition of Acetone and n-Heptane of the considered labs

The z scores demonstrate that almost all considered labs are able to determine a satisfactory mean

of the MIN lowest temperature of ignition of Acetone and n-Heptane. All these labs are within the

range from -2 to 2 (satisfactory). One lab has a result with a z-score just over 2, which is a questiona-

ble result. No lab has unsatisfactory results.

Conclusion: The aim of this interlaboratory test is met. A clear picture concerning precision parame-ters of the MIN lowest temperature of ignition of the method EN 14522 ( section 3) could be deter-

mined. The ratio between repeatability s.d. sr and reproducibility s.d. sR of Acetone for the considered

labs is approximately 1:3. Thus, at the testing of Acetone a potential of improvement of the method

exists. However, due to the application of a robust statistical method (DIN 38402-45 (=ISO/TS 20612))

the recalculated robust mean values of the MIN lowest temperature of ignition of the considered labs

for Acetone (527,5 C) and for n-Heptane (220,4 C) can be recommended as reliable values for the

verification of the apparatus according to EN 14522, Annex A / IEC 60079-20-1, part 7.

PROLab Plus

z-score-3 -2 -1 0 1 2 3 -3 -2 -1 0 1 2 3

Labo

rato

ry

70

106

201

233

234

248

250

251

472

840

908

961

962


36 BAM / PTB

7.2.3.2 Measurement uncertainty of the lab and validity for other test substances The results of the MIN lowest temperature of ignition (MINLTI) according to method EN 14522 / IEC

60079-20-1, part 7 are generally affected by the measurement uncertainty of a laboratory.

Expanded measurement uncertainty (k=2) on the basis of the reproducibility s.d. sR Results and especially the reproducibility s.d. sR obtained in interlaboratory tests are a valid basis for

measurement uncertainty evaluation ([6], [7]).

The following equation applies:

Laboratorys result = MIN lowest temperature of ignition MINLTI U [C],

at which in this interlaboratory test U denotes the expanded measurement uncertainty with k=2 (cov-

erage factor k section 1 Glossary)

Furthermore, the measurement uncertainty depends on the test sample ( Table 7-12). For the sam-

ples considered in this interlaboratory test the expanded measurement uncertainties (k=2) are given

as follows, where the values of the reproducibility s. d. sR (depending on the sample) were taken from

Table 7-12:

Acetone

Laboratorys result = MINLTI 2 7,9 C = MINLTI 15,8 C (k=2)

n-Heptane

Laboratorys result = MINLTI 2 2,5 C = MINLTI 5,0 C (k=2)

at which in this interlaboratory test MINLTI denotes the MIN lowest temperature of ignition.

Conclusion: It can be generalised that the expanded measurement uncertainty U (for k=2) for the MIN lowest temperature of ignition is not higher than 16 C for Acetone and n-Heptane. The meas-urement uncertainty cannot be ignored and must be considered if results of the MIN lowest tempera-

ture of ignition should be used in practice.


BAM / PTB 37

Validity of the measurement uncertainty for other test substances

Please note! It must be considered that the expanded measurement uncertainty U (k=2) calculated by the equations above can only be used by the lab, if the following criteria are fulfilled (Table 7-13),

[6]:

Table 7-13: Criteria to express the expanded measurement uncertainty U (k=2) by the aid of the repro-ducibility s.d. sR obtained by the interlaboratory test [6]

Criterion Content

Criterion 1 Method EN 14522:2005 / IEC 60079-20-1, part 7 is applied.

Criterion 2 Test conditions must be comparable to those of the interlaboratory test and the tested substance must be comparable to the interlaboratory test samples Acetone and/or n-Heptane.

Criterion 3 Trueness of the results of the lab must be established.

Criterion 4 Near agreement between the lab-specific repeatability standard deviation for certain samples and the repeatability standard deviation obtained in this interlaboratory must be established.

Conclusion: The aim of this interlaboratory test was to check and if necessary to recalculate the veri-fication values of Acetone and n-Heptane (MIN lowest temperature of ignition) of the method EN

14522:2005, Annex A / IEC 60079-20-1, part 7 and to assess the method ( section 3). The meas-

urement uncertainties determined can be assessed as highly acceptable for these interlaboratory test

substances. However, it must be considered that the expanded measurement uncertainty U (k=2) can

only be used by the lab, if special criteria are fulfilled (Table 7-13).


38 BAM / PTB

7.2.4 Temperature gradient inside the 200 ml Erlenmeyer flask

An acceptable precision of the method EN 14522 / IEC 60079-20-1, part 7 was demonstrated by the

results of the considered labs ( section 7.2.3.1). Thus the quality of the temperature conditions in

the 200 ml Erlenmeyer flask of these labs can be assumed as suitable for measuring the MIN lowest

temperature according to method EN 14522:2005 / IEC 60079-20-1, part 7. Therefore, the tempera-

ture gradient inside the 200 ml Erlenmeyer flask at two positions (2,5 cm and 6 cm above the bottom

of the flask) was determined based on the results of the considered labs (including lab 472) of TS 1

of this interlaboratory test ( Table 7-11).

7.2.4.1 Total robust mean value and reproducibility of the temperature gradient inside the 200 ml Erlenmeyer flask

A summary of the obtained total robust mean values and the reproducibility standard deviations6 (

se

interlaboratory test 2012-2013 on the method en 14522_2005

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