Gas Conditions in Mine Shafts
Gas Conditions in Mine Shafts
regulations to be implemented in shafts or pits that are hazardous because of escaping methane or hydrogen. So-called dust-and-gas conditions are implemented if, in addition to gas, a shaft is unsafe because of explosive dust.
Shafts in which the presence of methane has been detected, even if on only one occasion and in only one seam, are treated as hazardous. Shafts are classified in four categories (see Table 1) depending on the gas abundance.
| Table 1. Mine-shaft categories | ||||
|---|---|---|---|---|
| I | Categories II | III | Special category | |
| Note: In classifying mine shafts according to gas-abundance categories, 1 cu m of hydrogen is taken as equal to 2 cu m of methane | ||||
| Coal shafts | ||||
| Amount of methane escaping daily per ton of average daily output (cu m) ................ | 5 | 5-10 | 10-15 | Above 15, or shafts working seams in which there is a danger of blowouts of coal and gas and bleeding |
| Ore and nonore shafts | ||||
| Amount of flue gases (methane and hydrogen) escaping daily per cu m of average daily output (cu m)................to | 7 | 7-14 | 14-21 | 21 and above, or shafts working seams in which there is a danger of blowouts of coal and gas and bleeding |
The gas conditions provide for the implementation of systematic technical measures to prevent the accumulation of gas to dangerous levels and to prevent conditions that could ignite the gas. This is achieved by intensive ventilation of the mine workings and degassing of the minerals and surrounding rock, by the use of methods and machinery that provide for minimal gas accumulation, and by routine monitoring of the gas content in the air of underground workings by means of gas detectors and automatic control and emergency warning devices. The second group of measures consists in the prohibition of open flames, incandescent objects, and sparks in the shaft (this is achieved by the use of safety explosives and specially made electrical equipment and by observing precautionary measures during mining operations).
Gas conditions include a series of additional measures in the presence of bed accumulations of methane and during the working of seams in which there is a danger of sudden blowouts and bleeding.
S. IA. KHEIFITS