Mine fires remain one of the most potentially devastating underground incidents due to the prospect of multiple fatalities from the toxic products of combustion, the costly and time-consuming damage to critical underground infrastructure, and the damage to corporate standing and the ‘social license’ to operate. The behavior of mine fires is difficult to predict and often counter-intuitive, especially for intense fires where the amount of energy released by the fire in terms of natural ventilation pressures can dramatically change the volume and direction of airflow in ventilation circuits. This can have major and unexpected impacts on egress and entrapment, firefighting strategies, and the need for and design of fire protection systems.
This paper describes a technical study of the potential impacts of mine fires at the Freeport-McMoRan underground mining complex in Indonesia, examining seventeen potentially critical fire scenarios at PTFI as identified by a risk assessment. The range of fires examined includes mine mobile equipment fires, magazine fires, fuel bay fires, fire involving multiple light vehicles in a parking area, a compressor fire, an electrical sub-station fire, a conveyor fire, fire on an bus transporting personnel, spontaneous combustion fires, and fire in a long ‘naturally ventilated’ tunnel used by all vehicles to access the mine surface facilities, but physically unconnected to the mine.
A comprehensive review of available technical data from civil and mining sources in terms of the peak heat release rate (HRR) and HRR-time growth/decay curves was undertaken, as well as a careful review of existing data on human survivability limits. This led to the adoption of new design criteria for the modelling of fires as well as survivability limits. Modelling of each scenario was performed in VentSim Visual. To assist in communication of the complex fire behavior to management and workers, “real-time” animations showing direction, flow, and toxic gas concentrations were produced. The implications of the study in terms of egress and entrapment systems, incident management systems, and fire protection systems are also discussed.
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