Miners' Circular, Issues 58-61

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Bureau of Mines, 1947 - Mineral industries

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Page 15 - (b) Charges exceeding one and one-half pounds, but not exceeding three pounds, shall be used only if boreholes are 6 feet or more in depth, and explosives are charged in a continuous train, with no cartridges deliberately deformed or crushed, with all cartridges in contact with each other, and with the end cartridges touching the back of the hole and the stemming, respectively, and class A or class B permissible explosives are used.
Page 43 - ... material. The roofs of magazines so located that it is impossible to fire bullets directly through the roof from the ground need not be bulletproof, but where it is possible to fire bullets directly through them, roofs shall be made bullet-resistant by material construction, or by a ceiling that forms a tray containing not less than a 4-inch thickness of sand, or by other methods.
Page 38 - Metallic frames, casings, and other electric equipment that can become "alive" through failure of insulation or by contact with energized parts shall be grounded.
Page 42 - Pilled construction, such as concrete blocks with the cells filled with screened sand, weak concrete, cement mortar or other effective bullet-resistant filler; or exterior and interior wooden walls not less than 6 inches apart with the space between filled with screened sand, weak concrete, cement mortar or other effective bullet-resistant filler, and the exterior walls covered with sheet iron not lighter than No. 26 gauge, or other fireresistant material...
Page 45 - Each door shall be equipped with two mortise locks; or with two padlocks fastened in separate hasps and staples; or with a combination of...
Page 70 - ... 4. The charge shall be detonated with a permissible shot-firing unit 5. Cardox shall not be shot off the solid, over heavy rock binders or shale, or in a "tight
Page 60 - ... 1. The bodies and covers of special cars and the containers shall be constructed of nonconductive material. 2. If explosives and detonators are hauled in the same explosives car or in the same special container, they shall be separated by at least a 4-inch substantially fastened hardwood partition or the equivalent. 3.

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