US2892377A - Packages containing a material for use in blasting - Google Patents

Description

June 30, 1959 I s. H. DAVIDSON PACKAGES CONTAINING A MATERIAL FOR USE IN BLASTING Filed Nov. 21} 1955 FIG! INVENTOR SAMUEL HENRY DAVIDSON ATTORNEYS United States Patent PACKAGES CONTAINING A MATERIAL FOR USE IN BLASTING Samuel Henry Davidson, Largs, Scotland, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Application November 21, 1955, Serial No. 548,180

Claims priority, application Great Britain February 25, 1955 1 Claim. (Cl. 86-1) The present invention relates to the production and application of packages of materials suitable for use in blasting operations.

The explosive compositions employed for blasting operations are conventionally produced by mixing the ingredients together and packaging the resulting mixture as such in a container which, according to the nature of the explosive mixture and the situation in which it is required to be used, may be a thin paper wrapper, which may or may not be waxed, or a more substantial waterproof structure of a pliable or rigid construction, for example a rubberised cloth bag or a tinplate canister. More than 80 years ago, however, Sprengel proposed that there should be used for blasting operations explosive mixtures made up. from individually non-explosive constituents which were to be separately transported to the scene of the blasting operation and brought together into contact there for the first time. This practice would have obvious advantages as regards safety in storage and transport of the materials required and consequently in the cost of their carriage. Sprengel described three methods by which what have come to be known as Sprengel explosives could be made up.

Briefly Sprengels three methods consisted in mixing at the scene of the blast either a liquid non-explosive oxidising agent with a liquid non-explosive fuel or with a solid non-explosive fuel, or a liquid non-explosive fuel with a solid non-explosive oxidising agent. The present invention relates to a system corresponding to the lastmentioned method of Sprengels.

In certain countries the operation of bringing together the non-explosive oxidising agent and the non-explosive fuel at the scene of the blast is an operation that can only be carried out in accordance with the conditions laid down in Government regulations relating to explosives, but this does not detract from the advantage to be gained in respect of the cost of separate storage and transport of the non-explosive ingredients of the Sprengel explosive to the place where the oxidising agent and the fuel are to be brought together. The solid nonexplosive oxidising agents specified by Sprengel were the chlorates and perchlorates of the alkali metals and alkaline earth metals, and the nitrates of the alkali metals and alkaline earth metals which are not hygroscopic. The liquid fuels he suggested included carbon bisnlphide, nitro-benzene, alcohols and oils. plosives in which a stick or the like of potassium chlorate is dipped in an oil at the scene of the blast are obviously in accordance with the principle enunciated by Sprengel.

It does not appear to have occurred to Sprengel that in the production of explosives whose ingredients were to be mixed on the spot that ammonium nitrate would present certain advantages over the chlorates, perchlorates and nitrates of the alkali and alkaline earth metals, but explosives based on the use of ammonium nitrate and liquid organic fuels such as orthonitrotoluene and free from self-explosive sensitising ingredients have since been introduced into commerce. Such explosive compositions are not usually sensitive to initiation by means of commercial detonators and it is customary to employ a booster cartridge along with them.

The present invention depends on the fact that explosive compositions can readily be produced by wetting the surfaces of the particles of a mass of discrete ammonium nitrate particles with a non-explosive liquid organic fuel.

A package according to the invention consists at least essentially of discrete ammonium nitrate enclosed in a water-proof container having a cylindrical body portion longer than its diameter terminating at one end in an end wall and at the other end in a cover portion comprising an end wall at least a portion of which consists of soft elastic material which can be punctured by a needle of an injecting device and in which soft elastic material the resulting puncture closes at least sutficiently to render the container once more waterproof on removal of the needle.

The soft elastic material portion of the end wall may itself be of sealing characteristics so that on retraction of the needle the package will still prevent water surrounding it in the borehole from entering into contact with the explosive charge contained in it.

When it is required to make use of the package this is stood on end with the end wall comprising the portion of soft elastic material uppermost. The soft elastic material is next punctured and a predetermined quantity of the liquid non-explosive fuel is injected into the mass of ammonium nitrate particles. For this purpose a hypodermic syringe may conveniently be used, the needle servingto puncture the soft elastic material which may conveniently be india-rubber or a synthetic rubber. Provided this soft elastic material is of substantial thickness and is not under tension where it is punctured, the hole produced by puncturing it will tend to close itself when the needle of the syringe is removed and thus seal the package sufficiently to keep it waterproof until the moment when the blast is to be carried out.

The invention will now be described with reference to the diagrammatic drawing accompanying the provisional specification whereof Fig. 1 represents the package showing the ammonium nitrate particles and Fig. 2 is a detail showing the package in the act of being injected with the non-explosive organic fuel. 1 is a cylindrical sheet metal canister filled with a charge of discrete ammonium nitrate particles 2. 3 is an annular end wall of sheet metal on the lower side of which there is secured, in the central space, a rubber pad 4 of substantial thickness by means of an annular retaining member 5 soldered to the underside of the said sheet metal wall, as is best seen in Fig. 2. The rubber pad 4 is in compression between the metal of the wall 3 and the metal of the retaining member 5 and completely seals the space in the wall 3 out of which it bulges slightly from below. The circumferential portion of the end Wall 3 is turned over the cylindrical wall of the body portion of the sheet metal canister, so as to form a hermetic seal in known manner, for example with the interposition of a thin layer of rubber.

As is seen in Fig. 2 the operator pierces the rubber pad 4 with the needle 6 of a syringe 7 containing a charge 8 of the appropriate quantity of the non-explosive liquid organic fuel and discharges the syringe into the ammonium nitrate in the canister, which is desirably allowed to stand for some time in order that the ammonium nitrate particles may become as uniformly wetted as possible by the liquid fuel. To assist uniform wetting of the ammonium nitrate particles, the liquid fuel may advantageously contain a small percentage of liquid capable of reducing the surface tension between the ammonium nitrate and the liquid fuel, for example a long chain alkyl aryl dialkyl ester of phosphoric acid. When the operator withdraws the needle 6 after he has discharged the contents of the syringe 7, the rubber pad 4 resumes its former position and the puncture is sufficiently closed up to render the package substantially as waterproof as it was before. A primer cartridge furnished with a detonator is inserted into a borehole and the package containing the ammonium nitrate and the liquid fuel is super-posed on top of the primer cartridge for the purpose of carrying out the blast after the borehole has been stemmed. I

As the liquid organic fuel a wide Variety of compounds or mixtures may be employed, for example liquid aromatic and aliphatic hydro carbons, 'and non-explosive liquid aromatic nitro-hydrocarbons, alcohols, glyceride oils and other esters. The proportion of the liquid organic fuel should be such that an approximately oxygen balanced mixture will result from its admixture with the ammonium nitrate, for instance an accurately oxygen balanced mixture or one having an oxygen deficiency or excess not exceeding of that theoretically required to provide steam, carbon dioxide and nitrogen as the gaseous products of its self-combustion.

In general, the finer the grist of the ammonium nitrate the greater is the sensitivity to detonation, and the capacity of the resulting explosive to propagate its detonation. The capacity for such propagation is also greater, the greater the internal diameter of the container. Preferably the grist and bulk density of the ammonium nitrate are such that even in the absence of the liquid organic fuel it is still capable of propagating a detonation initiated in it, in the diameter corresponding to the internal diameter of the cartridge. For certain liquid organic fuels it is possible to obtain explosives in the above manner that are capable of having their detonation initiated by means of a commercial detonator, but sometimes it may be necessary to employ a primer cartridge in carrying out the blast. It has been found, for example, that propyl nitrate and a mixture of ethyl nitrate and ethyl alcohol in the proportion 2:1 by volume will produce explosives capable of being detonated by No. 8 lead azide detonators when added to ammonium nitrate of such grist that 100% passes a 36 B.S. screen,

passes a 100 B.S. oxygen balanced The ammonium nitrate used is of such a grist that passes a 100 ES. screen. The internal diameter of the tinplate containes 1 is 5" and the weight of the ammonium nitrate used in the cartridge which is 13.5 inches long is 9.2 lb., and the container 1 is sealed with a rubber pad 4 as shown in the drawing. By means of the needle 6 of the syringe 7 the ammonium nitrate is injected with orthonitrotoluene, the amount employed being 8 parts for every 92 parts of ammonium nitrate. Once the orthonitrotoluene has been injected the resulting explosive cartridge is allowed to stand for several hours before use. It is detonated in the borehole by means of a primer cartridge.

xampl 2 The procedure is the same as in Example 1, except that the liquid organic fuel is a hydrocarbon oil. The proportion used is 5 parts of hydrocarbon oil for every 95 parts ammonium nitrate.

What I claim is:

, A process for producing a blasting cartridge at the site of the blasting operation'comprising providing a waterproof container having a self-sealing end closure and being filled with discrete ammonium nitrate particles, inserting a syringe needle into said self-sealing end closure and'injecting a predetermined quantity'of a liquid fuel into said container thereby wetting the said ammonium nitrate particles, withdrawing said syringe needle from said self-sealing end closurethereby coincidentally sealing said container and achieving a blasting cartridge without loss of waterproof characteristics.

References Cited in the tile of this patent UNITED STATES PATENTS 861,209 Finch July 23, 1907 2,135,386 Crabbe Nov. 1, 1938 2,186,908 Page et al. Jan. 9, 1940 2,703,528 Lee et al. Mar. 8, 1955 2,754,755 Ruth et al. July 17, 1956

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