Proof of Concept of the Electronic Spark Test Apparatus on Existing Known Power Supplies

This project continued a long running research program into an electronic spark tester (EST) for methane based (gas group I) hazardous area applications. The EST is an alternative to the Spark Test Apparatus (STA), mandated by the IEC standard 60079-11 for spark ignition testing, a requirement of explosion protection by intrinsic safety (IS). The STA is a mechanical safety testing device creating laboratory scale explosions with sparking electrical contacts, and has long standing and well documented issues with reliability and reproducibility.

In this phase of research, significant improvements to the EST's testing logic have been made. Additionally, incremental improvements to the EST's hardware platform for reliability and robustness were carried out. This enabled the use of the EST to test a broad range of seven commercial IS power supplies for gas group I applications. The test results showed that under carefully calculated worst case scenarios, some products do not meet the safety factors mandated in IEC 60079-11. These products are nevertheless still likely to be compliant, as the EST's worst-case scenario may occur rarely in practical testing with the STA.

Additional testing with the EST was conducted on simple resistive circuits, in an attempt to reconcile the results with the ignition limit tables published in Annex A of the standard. The comparison shows relatively good agreement up to around 20 V. As most practical group I equipment has voltages lower than 20 V, the EST can in this regard be considered fit for purpose.

The report discusses pathways towards recognition of the EST in the IEC 60079 standards framework, which is the long-term goal of the research.