Document Type

Conference Paper

Publication Date


Publication Details

This conference paper was originally published as Mitchell, P, Controlling and Reducing Heat on Longwall Faces, in Aziz, N (ed), Coal 2003: Coal Operators' Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 2003, 234-245.


In recent years uncomfortably high ventilation temperatures have become more common on longwall faces in Australian coal mines. Increasing strata temperatures at relatively shallow depths in combination with high surface ambient temperatures, particularly in Queensland, have led to high intake temperatures. These have approached trigger levels that introduce reduced face operator exposure times. With the addition of heat from coal breakage and goaf caving on high production longwall faces the working environment has become uncomfortable and continuous exposure over a shift is potentially injurious to health. Typical strata temperatures at 200m depth are 35ºC increasing to 38ºC at 350m depth. The added heat from broken coal and rock on the face and in the goaf together with heat from machinery, that has been progressively increasing in capacity, results in wet bulb temperatures exceeding 30ºC and humidity of 95% to 100% on longwall faces. Management plans have introduced controls to limit continuous working times for personnel on longwall faces in the hot and humid conditions. This impacts on productivity and in some situations requires additional personnel in the panel crews. Increased ventilation quantities are a partial solution because evaporative cooling rates and reduction in effective temperatures are minimal in high humidity conditions and less effective in the already high air velocity currents on faces. High air velocities also introduce other face environment problems with dust, increased pressure differentials and goaf leakage quantities which re-enter as additional warm air back onto the face. Spontaneous combustion risks also increase in thicker seam environments. Depending on seam conditions more attractive approaches can be used such as three heading longwall development allowing a back return airway using the goaf as a partial heat sink and the introduction of direct cooling of air in the longwall panels by spray systems without disrupting the passage of employees and equipment.

Included in

Engineering Commons