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Zur Bestimmung der Deflagrationsfähigkeit von energiereichen Stoffen/ Gemischen wurde zuletzt ein Vier-Liter-Autoklav vorgeschlagen, der im Vergleich zu den derzeit gängigen Prüfmethoden eine Reihe von Vorteilen bietet. In diesem Beitrag wird der Frage nachgegangen, wie nicht-atmosphärische Bedingungen das Deflagrationsverhalten beeinflussen. Zur Beantwortung dieser Frage wurden weitere Experimente im genannten Autoklaven und in einem kleineren Autoklaven durchgeführt. Im Wesentlichen lässt sich feststellen, dass der Druck im Probengefäß vor Versuchsbeginn, insbesondere reduzierter Ausgangsdruck < 1 bar Auswirkungen auf das Deflagrationsverhalten hat. Das Vorhandensein einer reinen Stickstoffatmosphäre hingegen, beeinflusst das Deflagrationsverhalten nicht.
Many substances react with water in such a way that flammable gases are formed. For transport issues this reaction may possess a considerable hazard especially if the cargo is wetted by rain or by water from other sources. In the UN Recommendations on the Transport of Dangerous Goods these kinds of problems are addressed. The UN test N.5 'Test method for substances which in contact with water emit flammable gases' corresponds to this hazard. Classification according to the test method is done by measurement of the gas evolution rate of the flammable gas by any suitable procedure. At BAM a gravimetric approach is used to measure the gas evolution rate. In this paper we present the evaluation of the apparatus by means of an absolute calibration routine utilizing a reaction where a known amount of gas is produced as well as the evaluation of important parameters influencing the gas evolution rate using different substances. It can be shown that the apparatus is capable of measuring absolute gas volumes as low as 6 mL with an acceptable error of about 17% as determined from the reaction of Mg with demineralized water.
Dieser Beitrag beschreibt Untersuchungen zu Deflagrationen von Azodicarbonamid, welche erstmals in einem Vier-Liter-Autoklaven durchgeführt wurden. Zunächst wird die Reproduzierbarkeit der Messungen mit der neuen Apparatur überprüft. Anschließend wird ein Vergleich mit Messungen in einer offenen Apparatur hergestellt, welche zur Prüfung der Deflagrationsfähigkeit in VDI 2263-1 erläutert ist.
Zur Beschreibung der deflagrativen Zersetzungen werden die Kenngrößen Induktionszeit, Deflagrationsgeschwindigkeit, maximaler Druck, maximale und mittlere Druck- und Tempe-raturanstiegsrate herangezogen. Zusätzlich werden in weiteren Versuchen die während einer Deflagration entstehende Gasmenge und die Gasentwicklungsrate bestimmt. Abschließend werden die Druck- und Gasentwicklungsraten miteinander verglichen.
Aus den Arbeiten lässt sich folgern, dass der Vier-Liter-Autoklav zur Bestimmung und Beschreibung der Deflagrationsfähigkeit von Azodicarbonamid gut geeignet ist und im Vergleich zu Messungen in offenen Prüfanordnungen eine Reihe von Vorteilen bietet.
A four-litre-autoclave was used to perform deflagration tests in a closed vessel. The aim was to investigate the suitability of this autoclave and to evaluate different parameters influencing the deflagration.
The validation of test results showed that the autoclave is suited for the performance of deflagration tests. In comparison to tests performed in an open system according to VDI 2263-1 the results are in good agreement. In the closed vessel same characteristics as in the open test were determined. In addition, pressure rise and rate of pressure rise have been determined and used to characterise deflagrations.
The influence of sample weight, tube diameter, bulk density, initial pressure and temperature was investigated. Furthermore, the emerging gas amount and the rate of gas evolution were determined and compared with pressure curves. The use of a four-litre-autoclave for performing deflagration tests offers several advantages in comparison to an open test.
Laboratory test results are of vital importance for correctly classifying and labelling chemicals as “hazardous” as defined in the UN Globally Harmonized System (GHS) / EC CLP Regulation or as “dangerous goods” as defined in the UN Recommendations on the Transport of Dangerous Goods. Interlaboratory tests play a decisive role in assessing the reliability of laboratory test results. Interlaboratory tests performed over the last 10 years have examined different laboratory test methods. After analysing the results of these interlaboratory tests, the following conclusions can be drawn:
1. There is a need for improvement and validation for all laboratory test methods examined.
2. To avoid any discrepancy concerning the classification and labelling of chemicals, the use of validated laboratory test methods should be state of the art, with the results accompanied by the measurement uncertainty and (if applicable) the probability of incorrect classification.
This paper addresses the probability of correct/incorrect classification (for example, as dangerous goods) on the basis of the measurement deviation obtained from interlaboratory tests performed by the Centre for quality assurance for testing of dangerous goods and hazardous substances (CEQAT-DGHS) to validate laboratory test methods. This paper outlines typical results (e.g. so-called “Shark profiles” – the probability of incorrect classification as a function of the true value estimated from interlaboratory test data) as well as general conclusions and steps to be taken to guarantee that laboratory test results are fit for purpose and of high quality.
Safety experts, carriers or traders must be able to rely on the validity of the method and on correct results of safety tests and assessments in the laboratory.
Bundesanstalt für Materialforschung und –prüfung (BAM), Berlin and Physikalisch-Technischen Bundesanstalt (PTB), Braunschweig have extensive experience in the field of testing and assessment of physical hazards of chemicals.
Interlaboratory tests on different test methods have been performed by BAM and PTB during the last 10 years. Significant differences between the results of the participating laboratories were observed in all interlaboratory test. The deviations of the test results were not caused only by laboratory faults but also by deficiencies of the test method; i.e. many of the method descriptions are too ambiguous and allow divergences for interpretation.
Therefore, it is necessary to know exactly how good the method is that is used to classify dangerous goods or hazardous substances or to determine safety-relevant parameters. A key criterion is the measurement uncertainty.
One can choose simple methods with large error limits, but the measurement uncer-tainties should be known and always communicated together with the test results. This would allow safety specialists to be able to assess test results correctly and make well-founded decisions, e.g. for adequate protective measures.
Interlaboratory tests play a decisive role in assessing the reliability of test results. Participation in interlaboratory tests is not only a crucial element of the quality as-surance of laboratories; as such it is explicitly recommended in DIN EN ISO/IEC 17025. In addition, interlaboratory tests are also used to develop and validate test methods and can be used for the determination of the measurement uncertainty.
Therefore, the BAM and PTB continue to support the further development of the interlaboratory test programme of CEQAT-DGHS (Centre for quality assurance for testing of dangerous goods and hazardous substances, www.ceqat-dghs.bam.de), established in 2007. This programme is run by BAM in collaboration with the PTB and the QuoData Gesellschaft für Qualitätsmanagement und Statistik mbH, Dresden.
A new interlaboratory test for methods validation on the test method UN Test N.5 "Test method for substances which in contact with water emit flammable gases” is currently being prepared and will be carried out in 2018. Laboratories that specialise in this test are invited to participate in the interlaboratory test. Interested laboratories can check the details and register to participate in the interlaboratory test at the CEQAT-DGHS website.
The UN Test N.5 "Test method for substances which in contact with water with flammable gases", according to the Chapter 33.5.4 of the UN Manual of Tests and Criteria is one of the tests performed at BAM and was already investigated in detail. As a conclusion from these investigations a new verification method for the verification of this gas flow measuring test apparatus for the method UN Test N.5 was developed at BAM and is presented in this presentation as well as general aspects in the development of verification procedures will be explained. The planned interlaboratory test to validate the new verification method is discussed in this presentation.
The results of the round robin test on the solid oxidiser test have already been presented at IGUS EOS. In this presentation, we will show how the findings from the round robin test can be transferred into the regulations as easily as possible. This proposal serves as a basis for a proposal that can be discussed in the ECOSOC Sub-Committee of Experts on TDG (30 June - 04 July 2025).
Experiments according to a test specified in the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, and numerical simulations by means of a finite element method are employed to determine the self-accelerating decomposition temperature of acrylic acid in a railroad tank car. The results demonstrate that the transport of acrylic acid in big tank cars is safe as long as some basic conditions are taken into account.