FUNDAMENTALS
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spontaneous combustion |
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Precautions |
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Precautions
Mines with seams liable to spontaneous combustion must pay particular attention to ventilation and to certain mining processes:
- It is desirable to avoid high pressure
differentials, which suggests low resistance circuits (i.e. multiple headings)
so low pressure fans are adequate.
- Ventilating through goaf areas is not good
practice or at least requires good control. Bleeder systems are usually
avoided.
- Pillars should be adequate to minimize
crush, and cleaning off failed coal on ribs may be necessary even if not
desirable from a strata control aspect
- Pillars with high pressure differentials
across them may require grouting or similar to seal them
- If a gas drainage system under vacuum is to
be used, care is required to minimise leakage through the ribs into boreholes.
- Good housekeeping to avoid storage of cut
or broken coal is desirable. Belt cleaning standards may need to be particularly
high.
- Care is required in sealing old areas. When
ventilation is cut off there is a risk that a heating will occur when there is
an explosive mix in the sealed area. It is normal for the atmosphere in such an
area to be monitored and for the mine to be evacuated while the atmosphere is
within the explosive range.
Environmental monitoring systems in mines prone to spontaneous combustion typically include extensive monitoring of returns adjacent to goaves, particularly for carbon monoxide and oxygen, whilst inspections of return areas require particular attention to indicators of heatings (increased temperatures, odours, "sweating" of strata, etc).
Although a seam has been worked for long periods without any incidence of spontaneous combustion, it should be kept in mind that this does not mean it can never occur and mine officials should be observant for indications at all times.