Sold only by the Superintendent of Documents, U. S. Government Printing Office UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON PREFACE This handbook, Safety in Coal Mining, has been prepared at my request by the chairman of the mine safety board of the Bureau of Mines. The purpose of the handbook is to make available in convenient form a concise statement of practices and methods recommended by the bureau for the increase of safety in coal mining. Rapid growth in the use of machinery for cutting and loading coal, longer haulage ways, and the wider use of mechanical haulage have contributed toward economy in mining by making possible a larger output of coal without a corresponding increase in the number of workers. At the same time this mechanicalization of the mines has been accompanied by increased hazards from falls of roof and coal and from accidents in transporting the coal from the face to the tipple. Incidentally, also, the machines have introduced new hazards peculiar to themselves, although these hazards can not be classed among the major causes of mine accidents. Progress in accident prevention is indicated by either a larger output per accident or fewer accidents per employee; double progress is realized when increased production per accident accompanies a reduction in the accident rate per employee. It is hoped that this publication will prove helpful to safety engineers, mine owners, mine employees, and others in their endeavor to obtain the Nation's necessary fuel at a minimum cost in life and limb. The bureau plans to revise the handbook from time to time as developments in the industry, and further study and research, seem to warrant. SCOTT TURNER, Director. CONTENTS Preface__ Introduction__. Acknowledgments---. Accidents in coal mines, by causes-. Comparison of accident rates in mines_. Accident rates of mining and of surface industries. Page II 2 3 4 Detailed description of principal methods and instruments. Sampling and analysis. Analytical apparatus__. Analysis of hydrocarbon gases by fractional distillation at 25 Effect of inert gases on inflammability limits_ Classification of coal mines by gas content_. Notes on classification of mines by gas content__ Measuring the volume of mine air_ Methods of ventilating coal mines__ 25 26 28 29 29 30 31 Arrangements for ventilation in shafts, slopes, or drifts- Rock-dusting as a preventive of coal-dust explosions___ 46 Tentative Bureau of Mines specifications for rock-dusting to Summary of facts regarding coal-dust explosions and their prevention Coal-dust explosions in tipples and shafts_____ Ignition of gas or bituminous coal dust by explosives__ What are permissible explosives?_ 56 57 58 60 61 62 Specifications for a permissible explosive____ 63 Conditions prescribed for use of permissible explosives____ 63 Recommendations on preventing ignition of gas or coal dust. Explosives accidents other than those causing ignition of gas or Summarized recommendations on the transportation, storage, Lighting in and around the return exits of gassy mines__ Electrical machinery Electric power lines in gassy mines_ nes Portable storage batteries for mining machinery. Electric circuits in coal mines... Circuits leading underground_ Underground power, lighting, and miscellaneous circuits___ Liability of electrical machinery and circuits to ignite gas_ 81 Combination trolley locomotives, including trolley-- 82 Explosions and fires from leakage of natural gas and oil wells through coal mines--- Size of pillars around wells___. Precautions recommended for gas and oil wells driven through Entries--- Precautions_. Electric shocks_. Explosions of gas or coal dust-Continued. Barricades and refuge chambers_. Barricades___. Refuge chambers__. Falls of ground__- Timbering to minimize falls_. Discussion____ Timbering in rooms for roofs of average strength_ Timbering in pillar workings and retreating longwall. Haulage accidents___. Installations recommended for safety. Mine fires Page 85 85 86 88 88 89. 89 89 90 93 97 99 99 101 103 Speed of hoisting and lowering men in shafts and slopes |