The measurement and comparison of methane drainage efficiencies in longwall advance and retreat workings

For monitoring the flow of gas in methane drainage boreholes a flowmeter has been developed which is both sensitive and robust for this duty and which is safe for use in coal mines. The flowmeter and ancillary equipment has been used to monitor continuously changes in gas flow and other parameters as a function of position in the borehole and distance of the hole from the face. Several borehole surveys have been carried out, the results of which show that individual boreholes have a limited life, performance being influenced greatly by the nature of the strata, the method of mining and the method of standpipe seal employed.