TABLES 1. Principal causes of injuries at metal and nonmetallic mines, 1932-54_.. 3. Frequency rates of injuries from explosives at opencut metal and non- 4. Selected explosives accidents, 1940-44 5. Injuries from explosives at metal and nonmetal mines, reported to National Safety Competition, 1933-54--. 6. American table of distances for storage of explosives. 7. Resistance of copper and aluminum wire___ 8. Resistance of electric blasting caps, ohms per cap. Page 4 6 7 11 11 24 55 55 ACCIDENTS FROM EXPLOSIVES AT METAL AND NONMETALLIC MINES1 Metal- and Nonmetallic-Mine Accident-Prevention Course-Section 4 Revised by Frank E. Cash 2 PURPOSE AND SCOPE The first metal-mine accident-prevention course was prepared and published in 1942-45 as a series of seven miners' circulars (Nos. 51-57). The scope of the course has been broadened, revised, and brought up to date, and it is being published as a similar series of seven miners' circulars on accident prevention in metal and nonmetallic mines. These circulars are: 1. Accident Statistics (Miners' Circular 51), dealing with general statistics on accidents and injuries at metal and nonmetallic mines, including causes, costs, and the uses of investigations and reports of all accidents. 2. Falls of Rock or Ore (Miners' Circular 52), discussing the selection of mining methods to minimize the hazards of falling and sliding ground, the use of various types of support, and the protection of employees from falls of ground. 3. Hoisting and Haulage (Miners' Circular 53), presenting the hazards of hoisting and haulage in metal and nonmetallic mines and means of preventing accidents. 4. Explosives (Miners' Circular 54), giving information on accidents and injuries due to storing, handling, and using explosives in metal and nonmetallic mines and precautions for preventing them. 5. Fires, Gases, and Ventilation (Miners' Circular 55), explaining the causes of fires in metal and nonmetallic mines and the measures used to prevent, control, and extinguish them; describing gases found in mines and methods of detection and personal protection; and discussing necessity for and standards of proper ventilation. 6. Electrical and Mechanical Hazards (Miners' Circular 56), covering accidents and injuries from electricity and machinery and their prevention and injuries from falls of persons. 7. Health and Miscellaneous Hazards (Miners' Circular 57), including data on dust hazards, means of protection and sampling devices, protective clothing and equipment; and illumination, supervision, discipline, and safety training for employees in metal and nonmetallic mines. be These seven circulars do not contain all the material that may desired on every phase of accident prevention at metal and nonmetallic mines, but they will serve as basic discussion. To them may be added supplementary material of particular interest in the field where the 1 Work on manuscript completed July 1956. 2 Mining engineer, Bureau of Mines. course is utilized. This accident-prevention course, offered to the mining industry by the Bureau of Mines, has been compiled from studies by the Bureau and experience and knowledge gained by its engineers, to which is added information on safe mining practices made available by mining companies and their officials. This is the fourth section of the revised series of circulars that cover various phases of accident prevention in metal and nonmetallic mines; it gives information on accidents and injuries from storing, handling, and using explosives in metal and nonmetallic mines and discusses the precautions by which they can be prevented. The practical basis for these precautions is afforded by the examples of actual accidents and by their relationship to efficient blasting. ACKNOWLEDGMENTS Much of the original text is retained in the revised course on Accident Prevention in Metal and Nonmetallic Mines. The revision was made under the general supervision of James Westfield, Assistant Director-Health and Safety; William J. Fene, chief, Division of Safety; and Simon H. Ash, former chief, Safety Branch, Bureau of Mines. Frank E. Cash revised this miners' circular; supplemental material was supplied by the following Bureau engineers: Arthur M. Evans, Dallas, Tex. Emil W. Felegy, San Francisco, Calif. Louis H. McGuire, Seattle, Wash. The manuscript was reviewed by Catharine S. Hower, Lester L. Naus, Douglas H. Platt, and Roy G. Stott. Many of the illustrations were supplied by mining and manufacturing companies and taken from Bureau of Mines publications. USE OF EXPLOSIVES IN MINING HISTORY OF EXPLOSIVES IN MINES There are few industrial projects in which explosives are not used for one purpose or another, from removing tree stumps to tunneling through rock. Mining in all its forms makes a larger use of explosives than any other industry. It is said that gunpowder was first employed in 1627 for blasting rock in the mines of Austria, and by 1689 the practice had spread to Cornwall, England. Electric firing was first used in 1823 and was followed by the invention of safety fuse in 1831. About 1862 the successful manufacture of guncotton provided the first alternative for black blasting powder. This was followed by the introduction of dynamite in 1867 and the use of mercury fulminate in detonators about the same year. Later it was discovered that guncotton and nitroglycerin could be combined to form gelatin dynamite, and many specialized forms of explosives have been perfected. CONSUMPTION OF EXPLOSIVES In 1952 metal mines in the United States used approximately 7 tons of black blasting powder, 31 tons of permissibles, and 75,574 tons of high explosives; quarries and nonmetallic mines consumed approximately 553 tons of black blasting powder, 381 tons of permissibles, and 82,793 tons (including 37 tons of LOX) of high explosives. Metal mines, nonmetallic mines, and quarries used about 10.6 percent of the black blasting powder and 42.1 percent of the high explosives (including permissible and LOX explosives) used during 1952. In metal mines, 99.9 percent of the explosives used were high explosives other than permissibles.3 NATURE AND HAZARDS OF EXPLOSIVES Explosives are substances (or mixtures of substances) that have the property of rapid and violent change to gaseous form upon the application of shock or high temperature. Except for black blasting powder, commercial explosives have been modified and improved over past years to a degree that makes possible their handling, storage, and use with reasonable safety as long as the utmost care is used at all times. The relative safety that can be maintained by careful observance of simple precautions is borne out by the infrequency of accidents during the storage and transportation of explosives and by the use of great quantities of explosives under properly controlled conditions without accident. The inescapable necessity for constant care to maintain safe conditions in utilizing explosives is plainly evident in the histories of those types of explosives accidents that regularly occur. EXPLOSIVES INJURY STATISTICS Explosives accidents have been and still are a major cause of fatalities in metal and nonmetallic mines. Falls and slides of rock or ore, hoisting and haulage, and falls of persons have caused greater numbers of fatal injuries, but explosives accidents still rank with these as one of the serious hazards of mining. The relative percentages of fatal and nonfatal injuries from these and other principal causes for 1932–54 are shown in table 1 in the order of the frequency of the total (fatal and nonfatal) injuries. The injuries attributed to explosives at metal and nonmetallic mines (underground and opencut) constitute 9.9 percent of the fatal and 0.8 percent of the nonfatal injuries from all causes. At underground mines these injuries make up 10.1 percent of the fatal and 0.8 percent of the nonfatal injuries. At opencut mines they are 7.6 percent of the fatal and 1.3 percent of the nonfatal injuries. 3 Harrington, D., and East, J. H., Jr., Safe Storage, Handling, and Use of Commercial Explosives in Metal Mines, Nonmetallic Mines, and Quarries: Bureau of Mines Inf. Circ. 7674, 1954, 28 pp. (rev. of Inf. Circ. 7380). TABLE 1.-Principal causes of injuries at metal and nonmetallic mines, 1932-54 A review 45 of injuries from explosives in the iron-ore mines of Lake Superior for 1944-54 revealed that there were 9 fatal and 59 nonfatal injuries (total, 68), which is approximately 0.7 percent of the total injuries from all causes. These 68 injuries resulted in a time charge of 66,898 days, which is 3.8 percent of the total days charged to injuries from all causes. The 9 fatal and 58 of the nonfatal 4 Cash, Frank E., Accident Experience, Iron-Ore Mines, Lake Superior District: Bureau of Mines Inf. Circ. 7410, 947, 11 pp.; and Inf. Circ. 7510, 1949, 16 pp. 5 Lake Superior Mines Safety Council, Review of Accidents in the Lake Superior District: Proc., 1949, pp. 21-34; 1950, pp. 16-30; 1951, pp. 90-107; 1952, pp. 150-164; 1953, pp. 121-137; 1954, pp. 69-88; 1955, pp. 98-117. |