Validation of a new standard for safety characteristics of hybrid mixtures: HYBRID II

Abstract

Safety characteristics are used for the safe operation of processes. In a first step it is checked whether the used component is combustible and if so, in which quantities respectively in which concentration if mixed with air (explosive region) determining the lower and the upper explosion limit. If it can't be guaranteed that the process is run outside the explosive region, constructive measures may be undertaken, as for technical processes it is often assumed that an ignition source is available. Designing protection measures requires explosion characteristics to be determined, namely the maximum explosion pressure (p_max) and the maximum rate of pressure rise (dp/dt)_max.Safety characteristics of single-phase components (solid, liquid or gas) can be determined according to standards that were developed 40 years ago and are continuously improved. For hybrid mixtures containing a flammable gas and a combustible dust there has been an approach in the 80^s but it has never been improved nor applied ever since (ISO 6184-3). A new approach by four German research facilities and the German Institute for standardization (DIN) with the aim of developing a new standard was launched in 2019. In 2022 the key findings led to a first international round robin test with eleven participating facilities from seven countries (Spitzer et al. (2023)). The dust component was corn starch and methane was chosen as gas component.

In order to strengthen the data foundation before finalizing and publishing the new standard, a second round robin test was initiated with hydrogen as gas component and lycopodium as dust. The dust was provided by Otto-von-Guericke University of Magdeburg (OvGU), tested and sent by the German National Metrology Institute (PTB) to the participating facilities.

The paper will summarize the findings and their influence on the new standard.