Monitoring the potential for explosion in an underground coal mine traditionally centres on using the Coward Triangle, the Hughes Raybould Diagram, the USM explosibility diagram or the Ellicott diagram. None of these allow for analytical trending over time, it is difficult to determine rates of change of gas atmospheres using these techniques and thus predict if and when an atmosphere may become explosive. The Ellicott X Y diagram was an attempt to overcome this, This diagram suffers from the lack of bounds and the absence of an easy way to link the values to the limits of reality eg, fresh air, completely inert or completely fuel rich. In addition it requires separate plotting of the two parameters X and Y against time. Mines rescue guidelines and re-entry guidelines outline zones for safe entry and zones for no entry. Plotting these zones accurately on the X Y diagram is problematic, as there are four zones of interest – air rich, fuel rich, explosive and inert. Each of the three non-explosive zones would have different X and Y values to set as alarm points, making simple graphics impossible. This paper outlines a novel technique that allows for the plotting of the percent flammability independent of which zone the gases are in and indicating the zone separately. This enables easy time based trending to occur. This should enable wider acceptance and better understanding of explosion risk Monitoring the potential for explosion in an underground coal mine traditionally centres around using the Coward Triangle, the Hughes Raybould Diagram, the USM explosibility diagram or the Ellicott diagram. None of these allow for analytical trending over time, it is difficult to determine rates of change of gas atmospheres using these techniques and thus predict if and when an atmosphere may become explosive. The Ellicott X Y diagram was an attempt to overcome this, This diagram suffers from the lack of bounds and the absence of an easy way to link the values to the limits of reality eg, fresh air, completely inert or completely fuel rich. In addition it requires separate plotting of the two parameters X and Y against time. Mines rescue guidelines and re-entry guidelines outline zones for safe entry and zones for no entry. Plotting these zones accurately on the X Y diagram is problematic, as there are four zones of interest – air rich, fuel rich, explosive and inert. Each of the three non-explosive zones would have different X and Y values to set as alarm points, making simple graphics impossible. This paper outlines a novel technique that allows for the plotting of the percent flammability independent of which zone the gases are in and indicating the zone separately. This enables easy time based trending to occur. This should enable wider acceptance and better understanding of explosion risk.
History
Citation
David Cliff, An improved technique for monitoring explosibility of gases, Proceedings of the 2020 Coal Operators' Conference, University of Wollongong - Mining Engineering, 12-14 February 2020, University of Wollongong, 295-303.