Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42D—BLASTING
  • F42D5/00—Safety arrangements
  • F42D5/04—Rendering explosive charges harmless, e.g. destroying ammunition; Rendering detonation of explosive charges harmless
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B33/00—Manufacture of ammunition; Dismantling of ammunition; Apparatus therefor
  • F42B33/06—Dismantling fuzes, cartridges, projectiles, missiles, rockets or bombs
  • F42B33/067—Dismantling fuzes, cartridges, projectiles, missiles, rockets or bombs by combustion

Definitions

• the present invention relates to a method of disarming an unexploded blasting charge in a drill hole.
• a cartridge for disarming an unexploded blasting charge in a drill hole comprising:
• said pyrotechnic composition including an igniting charge arranged to ignite said pyrotechnic composition, said pyrotechnic composition including a metal powder fuel and a metal oxide serving as an oxidizer, said composition upon ignition undergoing an exothermic reduction- oxidation (redox) reaction arranged to burn away said blasting charge.
• redox reduction- oxidation
• Dynamite is usually sold in the form of cardboard cylinders about 20 cm (8 in) long and about 3.2 cm (1.25 in) in diameter, with a weight of about 190 grams. It consists of a mixture of nitroglycerine, an absorbent, and possible additives, like a stabilizer, a freezing point depressant, and a brisance improver. Dynamite will not detonate by heat and is moderately sensitive to shock. Shock resistance tests are usually carried out with a drop-hammer: about 100 mg of explosive is placed on an anvil, upon which a weight of between 0.5 and 10 kg is dropped from different heights until detonation is achieved.
• mercury fulminate detonates with a drop distance of 1 to 2 cm, nitroglycerin with 4 to 5 cm, dynamite with 15 to 30 cm, and ammoniacal explosives with 40 to 50 cm.
• US 6,765,121 B2 discloses a method and an apparatus for neutralization of the explosive content of mines and unexploded ordnance ("UXO").
• UXO unexploded ordnance
• Such ordnance includes not only unexploded shells, rockets, and fuses, but also ordnance that is designed to explode on contact or is triggered to explode by another activation mechanism, such as a detonator, such as a land, underwater, or shallow water mine.
• a detonator such as a land, underwater, or shallow water mine.
• the method comprises reacting, on or near the surface of the mine or UXO, a charge of a compound that reacts with an extremely high heat-release rate.
• the intense exothermic reaction generates high temperature combustion products that will melt, burn, or otherwise disrupt, a metal, plastic, composite, or wooden casing, thus leading to combustion or decomposition of the explosive.
• the high temperature in the casing decomposes the content thereof, causing the pressure in the casing to rise, fracturing the casing before the explosive detonates.
• the disrupted casing enables ignition of a large area of the explosive charge and provides easy access for atmospheric air to support active burnout of the explosive.
• WO 2009/120139 discloses a powder charged rock cracker cartridge of the kind stated in the second paragraph above.
• the pyrotechnic composition is gun powder, and the cracker cartridge satisfies the requirements of lowest explosive classification, which allows transportation and storing without those rigorous safety rules that apply for higher explosive classifications. Further, the cracker cartridge is easy to manufacture and easy to use, including easy to prime as well as to unprime safely on the working place.
• the object of the present invention is to provide a method of and a cartridge for disarming an unexploded blasting charge in a drill hole.
• this object is achieved in that the method comprises the steps of:
• the invention may result in reduced costs, especially as in the preferred case a cartridge is used that already exist on the market. Moreover, the invention may result in increased safety, especially as in the most preferred case a specific extra safe cartridge is used that already exist on the market.
• the pyrotechnic composition contains thermite.
• Thermite is a pyrotechnic composition of metal powder fuel, e.g. aluminum (Al), and metal oxide, e.g. Fe 2 03 or Fe 3 0 4 .
• metal powder fuel e.g. aluminum (Al)
• metal oxide e.g. Fe 2 03 or Fe 3 0 4 .
• redox reduction- oxidation
• the reaction is used in thermite welding, e.g. to join rail tracks, and in demolition of munitions, and occurs, because aluminum forms stronger, more stable, bonds with oxygen than iron.
• the same reaction applies to other metal powder fuels and other metal oxides, but as aluminum has a high boiling point and a low melting point, so that the reaction can occur mainly in the liquid phase, and both aluminum and red iron(III) oxide are inexpensive, a mixture of aluminum and red iron(III) oxide is preferred.
• the object stated above is achieved in that the pyrotechnic composition referred to in the second paragraph above includes a metal powder fuel and a metal oxide serving as an oxidizer, said composition upon ignition undergoing an exothermic reduction-oxidation (redox) reaction.
• redox exothermic reduction-oxidation
• the pyrotechnic composition includes thermite.
• thermite is a pyrotechnic composition of metal powder fuel, e.g. aluminum (Al), and metal oxide, e.g. Fe 2 03 or Fe 3 0 4 .
• metal powder fuel e.g. aluminum (Al)
• metal oxide e.g. Fe 2 03 or Fe 3 0 4 .
• redox exothermic reduction-oxidation
• the metal fuel is selected from the group consisting of aluminum, magnesium, titanium, zinc, silicon, and boron.
• any reactive metal could be used instead of aluminum. This is rarely done, because the properties of aluminum are nearly ideal for this reaction:
• the oxidizer is selected from the group consisting of iron (III) oxide, iron (II, III) oxide, manganese (IV) oxide, chromium (III) oxide, silicon (IV) oxide, copper (II) oxide, bismuth (III) oxide, boron (III) oxide, and lead (II, IV) oxide.
• iron (III) oxide, iron (II, III) oxide, manganese (IV) oxide, chromium (III) oxide, silicon (IV) oxide, copper (II) oxide, bismuth (III) oxide, boron (III) oxide, and lead (II, IV) oxide hematite or red iron (III) oxide (Fe 2 0 3 ) is most preferred, but magnetite or iron (II, III) oxide (Fe 3 0 4 ) also works satisfactorily.
• fluoropolymers may be substituted for the metal oxides, PTFE with magnesium or aluminum being a relatively common example.
• Fluoropolymer containing pyrotechnic compositions are usually called “pyrolants”, but the word “thermite” is used interchangeably with, and more commonly than, "pyrolant”.
• the blasting cap may be a non-electric cap or a fuse cap. In most situations it preferably is an electric cap, e.g. an electrically triggered detonator, i.e. containing an easy-to-ignite primary explosive that provides the initial activation energy to start the detonation in the main charge.
• the igniting device is stored separately and not inserted into the main explosive charge until just before use, keeping the main charge safe.
• Fig. 1 shows a preferred embodiment of a cartridge in a cross sectional side view, suitable for disarming an unexploded blasting cartridge according to the invention
• Fig. 2 shows, at a larger scale, a preferred embodiment of an insert unit, which in Fig. 1 is shown inserted in the upper end of the cartridge, and
• Fig. 3 is longitudinal cross section through the primed cartridge of Fig. 1 and 2 inserted in a drill hole, where there is an unexploded blasting charge.
• the cartridge 1 may be seen to comprise basically two parts; an outer plastic sleeve 2 and an insert unit 25, which in turn comprises a plug 4 and an inner sleeve 7.
• the plug 4 and the inner sleeve 7 may, according to a preferred embodiment, be made of an acetal plastic material, more specifically of an acetal (POM) copolymer and are molded jointly to form an integrated unit.
• POM acetal
• the outer sleeve 2 may preferably be made of so called ABS plastic and has the shape of an elongated circular-cylindrical tube, preferably with a flat end wall 3.
• the interior of the outer sleeve 2 forms a main chamber 5 which is filled with a non-exploding pyrotechnic composition charge 6.
• the plug 4 has a circular-cylindrical outer wall 19, a preferably flat, annular end wall 20, which faces the main chamber 6 and applied against the powder charge 6, and a tubular portion 21, which defines a through hole 8 that is coaxial with the outer sleeve 2.
• Radial supporting beams 24 may be arranged to improve strength, preferably extending between the tubular portion 21 and the cylindrical wall. Wedge-shaped, material saving recesses 23 are preferably arranged between the beams 24.
• An upper flange is designated 22.
• the inner sleeve 7 preferably has a very thin wall 13. It may optionally be provided with longitudinal, external stiffening protrusions 14 in order to increase its strength. Its cylindrical inside surface is preferably completely smooth. Its nose portion 12 may be tapered. More specifically, the nose portion 12 is preferably tapered at an acute angle according to the disclosed embodiment.
• the plug 4 is pressed into the mouth section of the outer sleeve 2 so far that the flange 22 abuts the upper edge of the outer sleeve 2 and the end wall 20 of the plug with some pressure contacts the pyrotechnic composition charge 6.
• the inner sleeve 7 will be pressed into the non-exploding pyrotechnic composition charge 6, which is facilitated by its pointed nose portion 12.
• the amount of powder of the non-exploding pyrotechnic composition charge 6 is adapted to the space which shall accommodate the powder, e.g.
• the non-exploding pyrotechnic composition charge 6 will be compacted to some degree, which may be advantageous because that prevents the powder from moving to any essential degree during transportation, and it also guarantees a good contact between the outer surface of the inner sleeve 7 and the powder.
• the pressure exerted by the insert unit 25 may not be exaggerated such that the thin wall 13 of the inner sleeve 7 is damaged or pressed together to any significant degree.
• the interior inner sleeve forms a direct continuation of the through hole 8 in the plug 4 and it also has the same cross section shape and area as the hole 8.
• the hole 8 and the space in the inner sleeve 7 in combination form an integrated chamber, denominated priming chamber 9.
• that section of the priming chamber which is defined by the inner sleeve 7 is referred to as igniting chamber 11 in this context.
• a blasting cap 10 When priming the cartridge 1, which is carried out on the blasting site, a blasting cap 10 may be entered into the priming chamber 9.
• the blasting cap 10 may contain an igniting charge which can be ignited electrically, for example, and if desired also a delay element, all of which may be enclosed in a cylindrical capsule 15, e.g. of aluminum.
• blasting cap 10 When the blasting cap 10 is an electric one, it has two fuse wire leads 17, 18 (Fig. 3).
• blasting machine 26 Their outer ends are to be connected to an apparatus generally called a blasting machine 26.
• the cartridge 1 When the cartridge 1 is primed, it is inserted in a drill hole 100 in a surface of exposed rock 102 until it makes contact with the unexploded blasting charge 101 as shown in Fig. 3.
• the drill hole 100 may have a diameter within the range of 22-85 mm.
• the outer sleeve 2 of the cartridge 1 will have an adapted diameter to properly fit into the hole 100, i.e. in the range of 16- 80 mm, more preferred 30-50 mm.
• the inner ends of the fuse wire leads 17, 18 are connected to each other by a thin bridge wire in direct contact with the igniting charge.
• the non-exploding pyrotechnic composition 6 includes a metal powder fuel and a metal oxide serving as an oxidizer. Upon ignition, the composition undergoes an exothermic reduction- oxidation (redox) reaction producing a sufficiently high temperature.
• redox reduction- oxidation
• the non-exploding pyrotechnic composition 6 includes thermite.
• thermite is a pyrotechnic composition of metal powder fuel, e.g.
• the reactants are stable at room temperature, they burn with an extremely intense exothermic reaction when they are heated to ignition temperature.
• the products emerge as liquids due to the high temperatures reached (up to 2500 °C with iron(III) oxide) - although the actual temperature reached depends on how quickly heat can escape to the surrounding environment.
• Thermite contains its own supply of oxygen and does not require any external source of air. Consequently, it cannot be smothered and may ignite in any environment, given sufficient initial heat. It will burn well while wet and cannot be easily extinguished with water, although enough water will remove heat and may stop the reaction. Small amounts of water will boil before reaching the reaction. Even so, thermite is used for welding underwater. Consequently, even if the unexploded blasting charge 101 in a drill hole 100 is covered by rainwater, for example, the cartridge 1 of the present invention can be used to burn away the unexploded blasting charge 101.
• the thermites 6 are characterized by almost complete absence of gas production during burning, high reaction temperature, and production of molten slag.
• the fuel should have high heat of combustion and produce oxides with low melting point and high boiling point.
• the oxidizer should contain at least 25% oxygen, have high density, low heat of formation, and produce metal with low melting and high boiling point (so the energy released is not consumed in evaporation of reaction products).
• Organic binders can be added to the composition to improve its mechanical properties, however they tend to produce endothermic decomposition products, causing some loss of reaction heat and production of gases.
• the metal fuel is selected from the group consisting of aluminum, magnesium, titanium, zinc, silicon, and boron. In principle, any reactive metal could be used instead of aluminum. This is rarely done, because the properties of aluminum are nearly ideal for this reaction:
• the oxidizer is selected from the group consisting of iron (III) oxide, iron (II, III) oxide, manganese (IV) oxide, chromium (III) oxide, silicon (IV) oxide, copper (II) oxide, bismuth (III) oxide, boron (III) oxide, and lead (II, IV) oxide.
• hematite or red iron (III) oxide Fe 2 03
• magnetite or iron (II, III) oxide Fe 3 04
• Other oxides are occasionally used for special purposes but are not preferred in the present application, such as Mn0 2 in manganese thermite, Cr 2 0 3 in chromium thermite, quartz in silicon thermite, or copper (II) oxide (CuO) in copper thermite.
• fluoropolymers may be substituted for the metal oxides, PTFE with magnesium or aluminum being a relatively common example. Fluoropolymer containing pyrotechnic compositions are usually called “pyrolants", but the word “thermite” is used interchangeably with, and more commonly than, "pyrolant”.
• the temperature achieved during the reaction is dependent on the availability of oxygen.
• the type of metal oxide has dramatic influence to the amount of energy produced; the higher the oxide, the higher the amount of energy produced.
• a good example is the difference between manganese (IV) oxide (Mn0 2 ) and manganese (II) oxide (MnO), where the former produces a very high temperature and the latter is barely able to sustain combustion; to achieve good results a mixture with proper ratio of both oxides should be used.
• the reaction rate can be also tuned with particle sizes; coarser particles burn slower than finer particles. The effect is more pronounced with the particles requiring being heated to higher temperature to start reacting. This effect is pushed to the extreme with nano- thermites.
• ignition device 10 may be of various kinds a conventional blasting cap may be preferred.
• the blasting cap 10 may be a non-electric cap or a fuse cap, it preferably is an electric cap, more precisely an electrically triggered detonator.
• a blasting cap contains an easy-to-ignite primary explosive that provides the initial activation energy to start the detonation in the main charge.
• Explosives commonly used in blasting caps include mercury (II) fulminate (Hg(CNO) 2 ), lead azide (Pb(N 3 ) 2 ), lead styphnate (lead 2,4,6-trinitroresorcinate CeHNsOsPb) and tetryl (2,4,6- trinitrophenylmethylnitramine C7H5N5O8) and DDNP (diazodinitrophenol C6H 2 N 4 05).
• the cartridge 1 of the invention may advantageously be manufactured in a number of different standard lengths, corresponding to diameters and lengths of the blasting charges.
• Dynamite is usually sold in the form of cardboard cylinders about 20 cm (8 in) long and about 3.2 cm (1.25 in) in diameter, with a weight of about 190 grams (1 ⁇ 2 troy pound).
• a stick of dynamite thus produced contains roughly 1 MJ of energy.
• Other sizes also exist.
• the invention is not limited to what has been described above, but may be varied within the scope of the appended claims. It is evident for the skilled person, for example, that the expression plug has to be interpreted in a broad manner, e.g. also including use of an end wall member that may be arranged integrally with outer shell, and also other variations that are within the ambit of the normal design procedure of the skilled person producing such enclosures.
• the method of and a cartridge of the present invention are applicable for disarming an unexploded blasting charge in a drill hole by burning away the charge.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Drilling And Exploitation, And Mining Machines And Methods (AREA)

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• 2016
  • 2016-08-09 SE SE1651094A patent/SE542347C2/en unknown
• 2017
  • 2017-08-09 EP EP17751720.8A patent/EP3497399A1/de not_active Withdrawn
  • 2017-08-09 WO PCT/EP2017/070187 patent/WO2018029248A1/en unknown
  • 2017-08-09 CA CA3031356A patent/CA3031356A1/en not_active Abandoned

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