Testing, Evaluation and Development of Hydrogen Sensors for an Underground Mining Ventilation Test Facility

An underground mining ventilation testing facility (VTF) was designed and constructed at the HySA facility at the North-West University, South Africa. The purpose was to evaluate risks associated with different hydrogen storage technologies in a confined environment. The work included initial calculations of hydrogen movement in specific spaces and the development of simulation tools to compare these modelled results with experimental work. For this purpose, hydrogen sensors that could accurately measure hydrogen concentrations during a controlled hydrogen leak at the VTF were required. Hazardous hydrogen sensors capable of measuring >4% hydrogen are not readily available commercially. Typically, hydrogen sensors rated for hazardous environments are designed for safety actions (e.g., activating emergency measures when hydrogen is detected) at concentrations of 8%. (Measuring concentrations higher than this is not required for commercial use, hence there is no market for such sensors.) At the VTF, it is necessary to be able to measure hydrogen concentrations >4% in order to obtain information on the flammable hydrogen concentrations at specified distances and orientations around a controlled hydrogen leak. Initial experimental work was conducted at low pressures, resulting in very low hydrogen concentrations. Commercial available original equipment manufacturer (OEM) hydrogen sensors were capable of measuring 0.2% hydrogen, which, for the low pressures and gas flows here, proved sufficient to enable us to make sensible conclusions. However, higher pressures and gas flows are essential in practical use, hence higher concentrations of hydrogen need to be measured. A custom sensor was developed by HySA, while commercial sensors (OEM) were investigated. This work reports on the testing and evaluation of several hydrogen sensors. Results of initial ventilation tests are presented.