Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B33/00—Compositions containing particulate metal, alloy, boron, silicon, selenium or tellurium with at least one oxygen supplying material which is either a metal oxide or a salt, organic or inorganic, capable of yielding a metal oxide
  • C06B33/12—Compositions containing particulate metal, alloy, boron, silicon, selenium or tellurium with at least one oxygen supplying material which is either a metal oxide or a salt, organic or inorganic, capable of yielding a metal oxide the material being two or more oxygen-yielding compounds
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06C—DETONATING OR PRIMING DEVICES; FUSES; CHEMICAL LIGHTERS; PYROPHORIC COMPOSITIONS
  • C06C5/00—Fuses, e.g. fuse cords
  • C06C5/04—Detonating fuses

Definitions

• the present Patent refers to a process for production of a thermal shock tube and product thereof, applied as signal transmission device for connecting and initiating explosive columns, or as a flame conductor, usually complemented by a delay element or used as a delay unit, which uses a pyrotechnic mixture with low sensitivity to ignition by shock or friction, with low toxicity, which generates a spark with superior thermal performance, said process having the possibility of continuous and separated dosing of the individual non- active components, in conjunction with the formation of the plastic tube, making the process safer, and with a more accurate dosing, and said product maintaining the advantages of the current pyrotechnic shock tube relative to the shock wave propagating tube: larger transmission sensibility and sensitivity, propagation even with cuts or holes in the tubes and low risk transport classification, and presents additional advantages: use of low toxicity components, use of ordinary, low cost, low adhesiveness polymers, generation of a spark that propagates through knots, closed kinks or tube obstructions, and resistance to failure by attack of components of hot explosive emulsions.
• non-electric detonators or “shock tubes” are broadly applied for connecting and initiating explosive charges in the mining and quarry sector.
• Such devices marketed with brands like NONEL, EXEL, BRINEL, etc., came to substitute electric blasting caps ignited by metallic wiring, and represented a revolution in the market of detonation accessories, due to its easiness of connection and application, and to the intrinsic safety against accidental ignition by induction of spurious electric current.
• pyrotechnic shock tube A further development in the low energy transmission fuses was the invention of tubes that make use of pyrotechnic mixtures inside the tube, in substitution for high-explosive-containing powders.
• pyrotechnic shock tube Some of the processes and products with pyrotechnic mixtures, hereinafter referred as “pyrotechnic shock tube”, are the following:
• the blasting caps connected to the plastic tube are necessarily instantaneous, without delay elements into the cap, and so there was no concern of the inventor in optimizing the thermal action of a spark, nor in eliminating toxic components, nor in guaranteeing the crossing through restrictions in the tube, nor in reducing the sensibility of the mixture to friction and mechanical shock, not even with the adhesiveness of the mixture to the tube, nor with the resistance to the attack by hot hydrocarbons from the emulsion explosive. It is evident, by the patent's descriptive report, and for all of the examples, that its use as a delay element is limited to the range of tens of milliseconds, not being adequate for most of the delays used in field practice.
• Signal transmission tubes are usually complemented with the insertion of a delay blasting cap in its tip, such cap made of a metal cap containing two layers of explosive powder pressed inside, the bottom layer being a secondary high explosive, and the upper layer being a primary, flame-sensitive explosive, complemented by a delay element consisting of a metallic cylinder containing in its interior a compacted column of powdery pyrotechnic delay mixture and, frequently, an additional column of pyrotechnic mixture sensitive to the heat generated by the tube's shock wave.
• a delay blasting cap in its tip, such cap made of a metal cap containing two layers of explosive powder pressed inside, the bottom layer being a secondary high explosive, and the upper layer being a primary, flame-sensitive explosive, complemented by a delay element consisting of a metallic cylinder containing in its interior a compacted column of powdery pyrotechnic delay mixture and, frequently, an additional column of pyrotechnic mixture sensitive to the heat generated by the tube's shock wave.
• the reaction products are basically hot gases which, when leaving the final extremity of the tube, expand themselves with loss of heat, such heat loss inhibiting the ignition of the pyrotechnic delay mixture.
• Slower delay powders are particularly insensitive to the shock tube output. It is necessary either to add an additional column of sensitive pyrotechnic mixture to give continuity to the explosive train or to use pyrotechnic mixtures more sensitive to heat and with larger column length.
• A) Pyrotechnic mixtures use toxic components (K 2 Cr 2 0 7 , Sb 2 0 3 , Sb 2 0 5 ) and flammable solvents, demanding recycling of the solvents, handling cares, and appropriate waste disposal;
• the process of extrusion of the plastic tube includes the dosing of previously prepared sensitive pyrotechnic mixture, during the formation of the plastic tube, with safety risks in handling and process;
• pyrotechnic shock tube Like conventional shock tube, pyrotechnic shock tube doesn't resist to the aggression by the hydrocarbons present in emulsion explosives, and prolonged exposure leads to failures in propagation;
• powdered pyrotechnic mixture also presents a low adherence to the tube polymer, particularly in LLDPE;
• Pyrotechnic mixtures are not optimized to allow propagation through to closed knots, cuts or kinks.
• the process also includes the dosing of previously prepared sensitive pyrotechnic mixture, during the formation of the plastic tube, with safety risks in handling and process;
• the system makes use of direct tube-to-tube connections for supplying a time delay exclusively through a predetermined length of tube, and is limited to fast delays, in the range of tens of milliseconds, while field blasting operations demand delay timing up to 10 s;
• the thermal shock tube employs an optimized pyrotechnic mixture with low toxicity
• the product maintains some advantages of the current pyrotechnic shock tube in relation to conventional shock tube: a larger sensibility and sensitivity of propagation, propagation to cuts or holes, and low risk classification for transport;
• the spark of signal transmission is formed so much by gases as by melted metals, and so it crosses knots, closed kinks or obstructions in the tube, and presents an optimized heat transport by thermal conduction and convection, igniting less sensitive, slower delay columns directly.
• the thermal shock tube resists to the environmental exposure to marine Diesel oil present in the hot explosive emulsions, maintaining functionality even after 72 hours of exposure at high temperature (65 °C for 24 h + 40 °C for 48 h in pure marine Diesel);
• - Thermal shock tube has a propagation speed accuracy within +/- 1 ,67% from the mean speed, i.e., an error of +/- 20 m/s in 1,200 m/s, adding to electronic delay detonators only +/- 0.3 ms of error in a 21 m long tube.
• mixtures of powdered aluminum, whose temperature of Tammann is 193°C and ferrous-ferric oxide, Fe 3 0 4 , whose temperature of Tammann is 632°C are particularly difficult to start and propagate, while mixtures of powdered aluminum and potassium chlorate, whose temperature of Tammann is only 47,5°C, is especially dangerous.
• One of the invention bases is to obtain enough activation energy to warranty the initiation and propagation of the pyrotechnic reaction even with the contamination of the interior of the tube by hydrocarbon fuel coming from explosive emulsion, such contamination decreasing the enthalpy pyrotechnic reaction.
• potassium perchlorate potassium chlorate, antimony trisulfide, sulfur, potassium nitrate, ammonium perchlorate, sodium chlorate, or any substance whose temperature of Tammann is adapted to this purpose.
• the invention is also based, without being limited to this, in the observation that a pyrotechnic reaction that generates products with high thermal conductivity and thermal convection coefficient, will allow a better propagation continuity, and will ignite delay elements with greater thermal efficiency, allowing the use of smaller, slower delay columns without additional ignition elements.
• oxidation-reduction reactions we have:
• Examples of appropriate components for gas generation are antimony trisulfide, potassium perchlorate, potassium nitrate, sodium nitrate, ammonium perchlorate, sodium perchlorate, etc.
• Another knowledge taken into account as base for the invention is that certain products present lubricating properties and superficial adherence properties, what reduces the sensibility to the friction and mechanical shock of the mixture, and provides adhesiveness even to difficult polymers like pure LLDPE. Examples of such products are: talc (magnesium and aluminum hydrosilicate) and graphite.
• Another objective of the invention is to obtain an unpublished process in that the mixture of the oxidizers and additive is done in separate from the fuels or reduction agents, and that the final active mixture is obtained in the own plastic extruder, in an automated, continuous or semi-batch process, so that just a very small amount of pyrotechnic mixture is formed at any instant, minimizing the risks and effects of an accidental ignition of the tube during the industrial production.
• Another aspect taken as base for the invention is that, to propagate through eventual cuts or holes accidentally done in the tube during field application, the spark should be constituted so much by products of high heat transfer, as by gaseous products, in a way to happen both the heat transfer to allow the continuity of the pyrotechnic signal transmission as to allow the mechanical impulse for releasing of the spark for the open portion of the tube.
• the development of the optimized formulation for the thermal shock tube was accomplished by several practical tests. For these tests, formulations of powdered pyrotechnic mixtures were dosed by spraying in the inner diameter of melted pure LLDPE in a extruder, the tube was cooled, and stretched to obtain a 3.1 mm outer diameter, 1.4 mm inner diameter flexible tube.
• Conventional SURLYN shock tubes obtained from a major manufacturer, as well as prior art pyrotechnic shock tubes from the applicant, were sampled and tested as a comparison.
• Low energy detonating cord initiation 100 samples of 1 m long tubes are connected to a line of detonating cord with a core loading of 2 grams/m of PETN, through a "J" type connector, and the line of detonating cord is initiated. The number of tubes which failed to propagate is recorded as "percentage of failures in initiation by 2 grams /m detonating cord";
• Tube-to-tube "air gap” a 3 m long thermal shock tube is transversally cut at the middle length and their half tubes are moved away with a measured spacing, maintaining there alignment through an aluminum guide in "half-pipe” format. The largest distance in than the spark, when crossing the free gap among the tube portions, initiate the second portion in 5 successive samples, is recording as "all-fire air gap";
• the tubes are ignited and the percentage of failed tubes is recorded as "failures after exposure to the hot emulsion"; 9) Adherence of the mixture to the tube: 10 tube samples 5 m long are weight in an analytical scale with and accuracy of 0.0001 g. Afterwards, the interior of the tubes is flushed by compressed air with a flow rate of 0.3 Nm 3 /minute for 2 minutes, to remove the non- adhered powder. The tube is weighed again and the weight is recorded. The interior of the tubes is washed with a flow of sodium hydroxide aqueous solution for dissolution of the aluminum and perchlorate, and dragging of iron oxide and talc, eliminating the adhered powder. The empty plastic tube is weighed. After determination of the tube's inner diameter the superficial area is calculated and, by difference, the free powder load by area rate, the adhered powder load by area rate, and the percentile rate of free powder mass by total powder mass are calculate.
• powdered aluminum - 32% to 60%
• powdered fuels or reduction agents able to generate a high temperature spark such as magnesium, silicon, boron and zirconium could be used;
• ferric-oxide - Fe 2 0 3 ferrous oxide - FeO
• cobalt oxide cupric oxide - CuO
• cuprous oxide - Cu 2 0 could be used; - 20% to 40% of potassium perchlorate - KCI0 4 .
• Another substances of low temperature of Tammann able to lower the energy of activation of the pyrotechnic reaction and to generate enough gaseous volume to propagate through kinks, knots, or tube restrictions such as potassium chlorate, potassium nitrate, ammonium perchlorate, sodium perchlorate, sodium perchlorate, sulfur and antimony trisulfide;
• the components of the pyrotechnic mixture formulation can have combined characteristics, in other words, the same substance component can have more than a function as mentioned above at the same time.
• the characteristics of the components of the formulation can be applied to conventional shock tubes, individually or combined, with the aim of optimizing them to obtain a better performance, a higher safety in production and a decrease in the environmental and occupational health risks.
• FIGURE 1 shows the block diagram of the process for production of the thermal shock tube
• FIGURE 2 that shows the thermal shock tube spark, leaving the tube tip
• FIGURE 3 that shows, as comparison, the basically gaseous products of a conventional shock tube (prior art) when leaving the tube tip;
• the process for production of thermal shock tube has the following sequence:
• Additional steps of processing could include tube cooling, stretching of the tube to obtain tensile strength, thermal treatment of the tube, and other techniques conventional in the plastic processing area, without loss for the invention teachings.
• thermal shock tube uses conventional plastic tube, such as EVA, POLYETHYLENE, LLDPE or SURLYN, with outer diameter ranging from 2.0 to 6.0 mm and inner diameter ranging from 1.0 to 5.0 mm and containing 5 to 40 mg/m of pyrotechnic mixture adhered to its internal walls;
• plastic tube such as EVA, POLYETHYLENE, LLDPE or SURLYN
• FIGURE 2 shows the thermal shock tube spark when leaving the tip of the tube during propagation, such drawing representing a high velocity photograph of the tube spark, where can be seen the high temperature solid and melted products (1), such products including highly thermal conductive and convective melted iron, the gaseous products (2), responsible for the melted jet projection at the tube tip.
• FIGURE 3 shows, for comparison, conventional shock tube (prior art) basically gaseous products, when leaving the tip of the tube during propagation, such drawing also representing a high velocity photograph of the tube flame, where can be seen the basically gaseous products (1) being dispersed by gas expansion at the tube's end.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Air Bags (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Pipe Accessories (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2003
  • 2003-09-19 BR BRPI0303546-8A patent/BR0303546B8/pt active IP Right Grant
• 2004
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  • 2004-09-17 PA PA20048612701A patent/PA8612701A1/es unknown
  • 2004-09-17 US US10/944,921 patent/US20050109230A1/en not_active Abandoned
  • 2004-09-17 PE PE2004000907A patent/PE20050272A1/es not_active Application Discontinuation
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• 2006
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