Measurement of Helium Leakage Rates through Closures of Dangerous Goods Packagings for the Assessment of Potentially Explosive Mixtures in Freight Containers

Abstract

The objective was to find out whether an explosive atmosphere can be created in a freight container by gaseous leakage flow of vapour‐air‐mixture through leaks in the closures of dangerous goods packagings filled with hazardous liquids. Because of high temperatures during intercontinental carriage, there is a gauge pressure in the free vapour phase inside the packagings which can cause a gaseous leakage flow. Two different methods were applied: Helium limit leakage rates for 23 quantitatively important hazardous liquids concerning their lower explosion limit (LEL) were calculated for a worst case transport scenario (Method 1). Helium leakage rates of five closure types of dangerous goods packagings with volumes of approximately 6 l were measured using the pressure technique by accumulation (Method 2). All types of closures of steel packagings were uncritical. The maximum measured leakage was 33% of the limit leakage rate. The leakage rates of screw closures of plastic jerricans can exceed the LEL if there are production‐related patterns such as non‐concentricity of the closures and flashes on the neck. Especially for plastic packagings it is important to minimize gaseous leakage flow, because an explosive atmosphere can also be reached by permeation of the individual filling substance or by a combination of both effects. For the assessment of potentially explosive mixtures in freight containers, both mass transfer mechanisms have to be taken into account. Copyright © 2015 John Wiley & Sons, Ltd.

Leakproofness of dangerous goods packagings—comparison of worst‐case limit leakage rates and sensitivity of the bubble test

“…At present, there are no quantitative limit leakage rates for dangerous goods packagings in the International Dangerous Goods Regulations. Therefore, limit leakage rates of a vaporous release of 23 liquid hazardous substances in relation to their LEL were calculated for a worst‐case scenario (intercontinental container transport; 20‐ft freight container; air change rate: 0.012 h at maximum load; average transport temperature: 30°C; transport duration: 8 weeks) . The LEL was chosen as criterion for the calculation of limit leakage rates, as it ensures a good comparability between the different substances.…”

“…The measured leakage rates of various closures of representative types of dangerous goods packagings are listed in Table . The measurements were carried out using the pressure technique by accumulation . This method is classified as a quantitative leak test method .…”

“…Under real conditions of transport of a packaging filled with a flammable liquid, there is a gauge pressure in the free volume above the liquid level, provoked by the high temperatures during transport . This gauge pressure is the driving force for the flow of the vapour‐air‐mixture from the inside through leaks in the closure area towards the outer atmosphere (atmospheric pressure) …”

“…The aim of this work is to compare the sensitivity of the bubble test according to the UN test conditions with quantitative limit leakage rates under normal conditions of carriage. These limit values have already been developed with respect to the LEL for a worst‐case scenario (intercontinental transport of filled dangerous goods packagings in freight containers) for 23 representative liquid hazardous goods . For better comparability between the different substances, they were converted to 100% Helium limit leakage rates under test conditions.…”

Study on Low Carbon Transition for Hazardous Chemical Packaging Based on Life Cycle Assessment and Grey Model

“…As a special part of commodity packaging, hazardous chemical packaging has gained much attention, since its characteristics are inflammable, explosive and corrosive which could bring adverse impact on human being and environment. Research on hazardous chemical packaging was mainly focused on the influential ensure product safety [17][18][19], such as safety test technology, product design, etc. However, there have been fewer studies on life cycle and carbon footprint.…”