On energy discharge profile in spark test apparatus

Even if the prospects for using hydrogen as an energy vector fluctuate, current trends will increase the incidence of hazardous areas, especially those due to hydrogen. In the context of increased intelligence implemented to control and improve the efficiency of technological systems, low-current installations are of greater importance. Certification is a process that confirms the implementation of explosion protection in equipment and systems through a legal means. An important step in this process, in addition to evaluation, is the testing of the equipment. For confirmation of the type of intrinsic safety protection by test, reference curves from the specific standard or the spark test apparatus (STA) are used. The method, which is based on the use of the STA, is influenced by a stochastic process. This raises problems with the consistency of the results. This fact was highlighted in a proficiency testing session, which at the end showed a dispersion of relative values in the range of -100%400%. With the present work, the authors aim to statistically analyze the discharges in terms of energy, identify and characterize an emerging dispersion profile. Preliminary tests have revealed the existence of additional noise that may affect the measurements; therefore, part of the present effort is to identify and filter out this interference. In the first part of the paper, the STA and its relevant parameters are presented. Also on this occasion, the test stand used to obtain the energy discharged into the device in its calibration process is presented. The next part was devoted to the presentation of the results and discussions. An important conclusion of the work is that, for the test conditions used, the energy discharged in the STA exhibits nonuniform dispersion of energy values and is characterized by several attractors.