Handbook for Methane Control in Mining - AMMSA

130In the case of the abovementioned WestVirginia mine, any one of the followingmeasures would have reduced the chanceof an explosion:• Thoroughly ventilating the waterring space with compressed air.• Carefully checking for methaneusing a methane detector with aprobe inserted into the water ringspace.• Opening the access door withoutusing an acetylene torch.To avoid methane problems when dealingwith water rings, the appropriate action isto incorporate all three measures intostandard operating practice.Figure 9–3.—Water ring in shaft wall (adapted fromOakes et al. [2003].METHANE IN SHAFTS EXCAVATED WITH RAISE BORE DRILLSLike conventional shafts, raise bore shafts at coal mines must be well-ventilated and the methanelevel must be monitored frequently. Maksimovic [1981] reported on some methods to ventilateraise bore shafts. These involve moving air through the drill stem or the annular space betweenthe drill stem and the wall of the pilot hole. A more recent approach is to drill a second hole forventilation and methane sampling (Figure 9–4).The methods reported by Maksimovic involve the use of air compressors to inject air into theshaft in quantities ranging from 600 to 3,000 cfm, and vacuum pumps to withdraw air from theshaft in quantities ranging from 600 to 1,000 cfm. These are used separately or in combinationas follows:• Alternating the use of the air compressor and vacuum pump. Compressed air is injecteddown the drill stem 5 for a period of 2–4 hr, and then a vacuum pump is used for a shortinterval to bring an air sample through the drill stem to the surface for a methanemeasurement.5 At the same time, air can also be forced down through the annulus.