LJ. S. QEOLOOICAL SURVEY BULLETIN 423 PLATE I GAS AND DUST GALLERY NO. 1, PITTSBURG TESTING STATION. DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR ,ErrrN 423 A PRIMER ON EXPLOSIVES FOR COAL MINERS BY CHARLES E. MUNROE AND CLARENCE HALL WASHINGTON GOVERNMENT PRINTING OFFICE 1909 CONTENTS. Page. Introduction............................................................. 9 Combustion and explosion................................................ 11 Fire................................................................. 11 Combustible substances............................................... 11 Explosion ........................................................... 11 Dust explosions ....................................................^. 11 Air necessary to ordinary combustion.................................. 12 Oxygen of the air necessary for combustion............................ 12 Oxygen from saltpeter................................................ 12 Saltpeter supports combustion......................................... 12 Charcoal with saltpeter produces heat and gas.......................... 12 Sulphur is added to make the mixture ignite easily..................... 13 Chile saltpeter contains oxygen ..........................___:........... 13 Oxygen in other bodies............................................... 13 Nitric acid from saltpeter............................... .............. 13 Putting oxygen into cotton, glycerin, etc............................... 14 Sensitiveness and violence of fulminate of mercury..................... 14 Low explosives ....................................................... 14 High explosives...................................................... 14 Confinement essential to use of explosives............................. 15 Folly of attempting to make explosives ................................ 15 Explosives................................................................ 15 Gunpowder.......................................................... 15 Black blasting powder................................................ 15 Danger from dampness ............... ................................ 16 Keep powder dry .................................................... 16 Granulating powder.................................................. 16 Size of powder grains................................................. 16 Danger in using a mixture of different-sized grains...................... 17 Potassium chlorate................................................... 17 Nitrocellulose........................................................ 18 Nitroglycerin ......................................................... 18 Nitroglycerin freezes .................................................. 19 Liquid nitroglycerin is especially dangerous............................ 19 Dynamite............................................................ 19 Explosive gelatin and gelatin dynamite................................ 20 All explosives containing nitroglycerin freeze........................... 20 Dynamite cartridges.................................................. 20 Packing dynamite.......... i ......................................... 20 Nitrostarch ...................;...................................... 20 Ammonium nitrate................................................... 21 Nitro-substitutioii compounds......................................... 21 Why nitro-substitution compounds are so called......................... 21 Fulminates .^........................................................ 22 Danger with fulminates............................................... 22 Warning against manufacturing explosives ............................. 22 3 4 CONTENTS. 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Explosives for use in coal mines...---.-.....................__.....__...... 22 Number of explosives. ........_...................._.........._........ 22 Explosives in open work.. ........................._...___.____..__.__. 23 Explosives in inclosed work........................_..................' 23 Danger from flames in coal mines...................................... 23 Noxious gases ............ r ........................................... 23 Investigation by Geological Survey.................................... 23 Testing station at Pittsburg ........................................... 24 Explosives gallery No. 1.............................................. 24 Permissible explosives........-......-.---------...................... 24 Classification of permissible explosives................................. 25 Advantages of permissible explosives ................................... 25 Danger from permissible explosives.................................... 25 Freezing of permissible explosives..................................... 26 Danger from exposure to high temperatures............................ 26 Do not expose to sunlight.................................. '. .......... 26 Keep explosives dry.................................................. 26 Do not dry explosives too much ............................'...........' 26 Use explosives promptly.............................................. 26 Injury to cartridges from rough handling .............................. 27 Care in handling cartridges............................................. 27 . Shipment of explosives ............................................... 27 Storage of explosives ................................................. 27 Magazines ........................................................... 27 Detonators never to be stored with other explosives .................... 27 Opening boxes of explosives ................:......................... 28 Thawing frozen explosives............................................ 28 Thawers for explosives ............................................... 28 Complete thawing necessary ...................... .................... 28 Thaw houses......................................................... 29 Thaw houses not to be used for storage ................................ 30 Squibs, fuse, and detonators............................................... 30 Means of exploding explosives ........................................ 30 Miner's squibs ....................................................... 30 How sqnibs work...................^..................^.............. 30 Squibs should not be used in fiery mines............................... 30 Fuse ................................................................ 30 Action of fuse..............................................I......... 31 Testing fuse.......................................................... 31 Fuse injured by bad handling.......................................... 31 Care in cutting fuse ................................................... 31 Detonators.....-.-..--....--...-.--..........-...-.-.......-.....-... 31 Advantage in use of detonators........................................ 31 Grades of detonators ................................................. 32 Attaching detonators to fuse .......................................... 32 Fuse not to be used in fiery mines.......... i........................... 32 Fuse and detonators must be of'standard size........................... 32 Electric detonators................................................... 32 Grades of electric detonators .................'......................... 33 Firing electric detonators ............................................. 33 Delay-action electric detonators ....................................... 33 Danger in use of detonators........................................... 34 CONTENTS. 5 Page. Mining coal with explosives............................................... 34 Conditions in coal mines ............................................... 34 Shooting off the solid.....................'............................ 34 Need of slow-acting explosives........................................ 35 Dependent shots .....................................'................ 35 Overcharging ........................................................ 35 Undercutting and shearing............................................ 36 Shearing............................................................. 36 Charge of explosive in shearing ........'............................... 37 Undercutting ........................................................ 37 Charge in undercutting ......'......................................... 37 Placing of the shots.................................................... 37 Advantage of small charges ............................................ 38 Depth of undercutting ................................................ 38 Care in using permissible explosive's ................................... 39 Dust must be wet down and removed.................................. 39 Humidifying mines................................................... 39 Shot firera ....:............................................-......... 40 Loading and firing charges of explosives................................... 40 Loading bore holes ................................................... 40 Primer .............................................................. 40 Density of charge...............:.:1.................................. 40 Loading black blasting powder........................................ 41 Tamping stick.................................................. ...... 41 Placing fuse and tamping ............................................. 41 Danger of firing untamped holes .....................................