Show permissible explosives bureau of mines making powder tests to determine efficiency washington D C feb 22 the united states bureau of mines charged with investigations looking toward a reduction in the number of death in the mines has just issued bulletin no 15 on the subject of explosives used in coal mines the investigations 1 were conducted by clarence hall W 0 snelling and S P howell and the purpose was to determine which explosives are the most suitable for use in coal rhines mines and the precise conditions under which they may be used with the greatest safety the general introduction to the bulletin written by charles E munroe consulting engineer of the bureau states the united states government does not compel nor prevent the use of any explosive or prescribe the conditions of use it only advises the public as to the character of explosives and asto as to the manner in which they should be used it is therefore gratifying to state that the manufacturers of explosives in this country operated cooperated co so promptly and so cordially in the endeavor to protect the lives and persons of those engaged in mining coal that by january L 1 1910 there had been received at the pittsburgh testing station of the bureau fifty one applications for the testing of explosives plo during that year sixty four of the explosives submitted were tested and thir ty six of these passed the tests required to place them on the list of permissible explosives plo the bulletin describes the method used in testing explosives and defines what a permissible explosive is on this subject W 0 snelling says in explosives for use in the open air such as for example quarrying or railroad excavation strength and efficiency in removing rock are the qualities that are most important and usually are the only ones that need consideration in the selection of a suitable explosive explosives that are to be used in tunneling must not only possess but also be of sc ss strength and efficiency such composition that upon exploding they will ivill not give off large quantities of poisonous or offensive gases in explosives intended for use in coal mines a further property is most important besides possessing the qualities es of strength efficiency in breaking down coal and f freedom from poisonous explosion products the explosives shou should id be of such nature as not readily to ignite explosive inix mixtures tures of gas or coal dust the underlying causes for one explosive being safer than another in the presence of explosive mixtures of gas or coal during the past dust have been investigated few years the many thousands ands of lives disasters have shown the lost in coal mine necessity of such investigations and have stimulated to a marked extent researches in regard to the preparation of explosives siAi suitable table for use in coal mining it has been found that every known explosive if fired in a sufficiently large charge will cause the ignition of an explosive gas mixture but explosives have been found to differ widely in regard to the amount that can be fired without causing such ignition ordinarily black blasting powder for example will cause the ignition of explosive gas mixtures very readily as little as 25 grams somewhat less than an ounce invariably serving to bring about this result certain other explosives in quantities as great as 1000 grams 2 15 1 5 pounds after repeated trials under conditions exactly similar to those used in testing black powder have invariably failed to cause ignition of the explosive gas mixtures in certain european countries where regulation of the manufacture and use of explosives is recognized as a proper means of safeguarding life and protecting users of explosives from dangerous compounds that might be made and sold by persons not possessing sufficient knowledge or technical skill all explosives ives intended for use in coal mining are subjected to tests to determine their fitness for such use in the united states authority controlling the use of explosives lies with the legislatures of several states up to the present day the regulations in diff different erent states have been far from and in many states have been inadequate accurate information in regard to the action of different kinds of explosive materials is necessary nece necessary for efficient legislation and such information has been nowhere available it is to remedy this condition and provide accurate data in regard to explosives that tests of coal mining explosives explosive sare are being made by the bureau of mines these tests serve to show which explosives are safe and which are dangerous for use in coal mining milling and to determine such other properties of explosives as are of importance in the safe and efficient use of these materials te rials all explosives that satisfactorily pass such tests as show that they can be fired in ill considerable qua qualities in explosive gas mixtures without causing ignition and in addition possess such qualities of stability etc as make them reasonably safe to handle and transport are termed permissible explosives only such explosives are deemed suitable le for use in coal mines in which dangerous quantities of fire damp or inflammable coal dust are likely to be met permissible explosives of most varied composition have been prepared but in all of them the explosive power is due to the reaction of oxygen with combus combustible tible elements such as carbon and hydrogen the composition of tile the explosives being such that the temperature res resulting uffing from this combustion is not so high nor so long continued as with ordinary explosives an inflammable gas mixture can be ignited either by a very high temperature acting for a short interval of time or by a low temperature acting through a longer space of time but if a low temperature only is produced by the explosive and this temperature is of very short duration the ignition of the explosive gas mixtures is much less likely accordingly the problem of making explosives for use in coal mines is seen to be in its simplest form the making of an all explosive that aI although though producing in a low temperature of short duration shall nevertheless produce a sufficient quantity of gases and at sufficient fent pressure to perform by their expansion the work for which the explosive is intended through scientific fie studies and experimentation manufacturers of explosives have found ways of obtaining this result nitroglycerin ammonium nitrate and other well known explosive materials are combined with various substances so as to form explosives that when properly used so greatly diminish the risk of accidental ignition of fire damp or coal dust that it may be said to be practically eliminated |