How to measure the angle of repose of hazardous substances in the test centres for dangerous goods packagings

Abstract

The flow properties of powdery or granular filling substances for dangerous goods packagings are safety‐relevant parameters. To specify the flow behaviour, the angle of repose is measured in the recognized test centres for dangerous goods packagings in Germany. Previous investigations performed on non‐hazardous substances revealed that some of the methods currently used have disadvantages in application. Additionally, for occupational health and safety reasons, it was generally viewed critically to carry out measurements of the angle of repose for dangerous goods at all. Instead, the dimensionless Hausner ratio to describe the flow behaviour was proposed. In this work, the investigations were extended to real hazardous substances to concretize the assessment. Five exemplary hazardous substances were tested for their angle of repose using the methods commonly applied in the test centres. The Hausner ratio was also determined. In addition, the influence of a different climatic preconditioning on the angle of repose measurement was examined using three selected non‐hazardous bulk materials. The results show that the measurement of the angle of repose is not fundamentally excluded for dangerous goods. However, for reasons of applicability, repeatability and occupational health and safety, only the ISO method can be applied for dangerous filling substances. This method provides conservative results regarding a safety‐related evaluation of flow properties for the transport of dangerous goods. In principle, both the ISO method and the determination of the Hausner ratio can be used for dangerous goods. It is also essential especially with finely powdered filling goods, to carry out controlled preconditioning.