RU2202100C2 - Electric detonator igniter - Google Patents

Abstract

FIELD: initiating and igniting means for mining, coal-extraction, oil-gas, and other industries. SUBSTANCE: molybdenum wire is used in igniter as fuse head and its igniter composition has following ratio, %: potassium perchlorate, 40- 80; boron (amorphous), 10-30; additional oxidant, 10-30; binder, 1.5-2.5 in excess of 100, where following compounds may be used as additional oxidants: lead dioxide, red lead, lead oxide, and lead chromate; for low-toxic igniters whose ignition products are free from highly toxic ignition products use may be made of bismuth oxide, barium chromate, and cupric oxide. Fluorine-containing elastomer, butadiene acrylonitrile rubber, and mixtures of butadiene acrylonitrile rubber and colloxylin may be used as binders. Igniter of proposed design is used to advantage as explosion means in extraction of minerals and in construction engineering due to increased safety current (minimum 1 A), improved protection against static electricity charges, reduced sensitivity of ignition head to heat and mechanical impacts. EFFECT: enhanced safety and reliability of igniter when used in group blasting. 4 cl, 3 tbl

Description

 The invention relates to the field of creating means of initiation and ignition and can be used in the manufacture of safe electric igniters (EV) for electric detonators (ED) for industrial use, used in mining, coal mining and other industries.

 At present, industrial EDs that are widely used in blasting in the mining and coal mining industries, geophysical explosions, have a high sensitivity to external influences (stray currents, charges of static electricity, etc.), which significantly increases the cost of mining and worsens the technical conditions safety due to possible premature explosions of charges.

 In recent decades, the risk of premature explosions has greatly increased. This is due to the fact that there are significantly more electrified mechanisms at the facilities where electric blasting is carried out, as well as a large number of products made from synthetic materials (pipelines, hoses, conveyor belts, etc.) that are capable of accumulating electrostatic charges under certain conditions.

 Electrically driven stray currents and leakage currents from electrical installations during mining can reach values up to 1 A (A.I. Lurie, "Electric Explosion of Charges", M., Nedra, 1973, p. 210).

 Thus, at present, there is a need for the creation of EV to ED with reduced sensitivity to stray currents, charges of static electricity, as well as with reduced sensitivity to mechanical and thermal effects of the ignition head of the EV. This is necessary both for the modernization of regular EDs, and for the creation of a new generation of safe EDs that do not contain initiating explosives.

 The use of EV is associated with the danger of premature operation under the influence of stray pickup currents or charges of static electricity. To prevent this danger, both different types of ignition compositions and various constructive solutions of EV were proposed. All known methods of protecting ED from charges of static electricity and stray currents can be divided into two groups: preventing the passage of a spark discharge through the composition of the ignition head of the EV and excluding ignition of the composition when passing through the incandescent bridge or discharge gap inside the head of the EV.

 The first group includes various methods of isolating the igniter head from the ED liner by coating the igniter head with insulating varnishes and enamels or using tubes and bushings (Czechoslovakia patent 152844 dated 04.15.74, class F 42 B 3/18), as well as due to applying a conductive coating to the head of the igniter, discharge discharge from the head to the wires of the EV (Austrian patent 291076 from 10.15.70, CL 06 C 3/02).

 These methods to some extent protect the EV head from discharges of static electricity, however, they do not protect against stray currents (they do not increase the safe current).

The second group of ways to protect ED from charges of static electricity, as well as stray currents include the use of incandescent bridges of increased diameters (nichrome, constantan), bypassing the incandescent bridge outside the ignition head using a piece of wire (Czechoslovakia patent 101556, class 78e ³ , 1961 ), as well as the use of igniter compositions with reduced sensitivity to thermal momentum.

 However, as the analysis of literature data shows, by increasing the diameter of the incandescent bridge, as well as bypassing it, it is impossible to increase the safe current to 0.8-1 A without a significant increase in the ignition pulse and a decrease in the number of products undermined in groups.

Known ED with EV, which has increased resistance to static charges and stray currents (US patent 3282828 from 11/22/66, CL 102-28). The essence of the invention lies in the use of igniter compositions boron - lead oxide, boron - lead minium (B - Pb ₃ O ₄ ), which have high levels of breakdown voltage.

 The disadvantage is the complexity of the design of the product, since the composition is low-gas, a new design of EV is needed. The low sensitivity to the heat pulse of the igniter composition requires a large ignition energy, which cannot be provided by explosive devices for group detonation of products.

An electrically igniter device is known (US patent 345045 dated 06/17/69, class F 42 C 11/00), which contains an incandescent bridge with a resistance of 0.3-1.0 Ohms, surrounded by an ignition composition of bulk density. The composition contains from 10 to 90% magnesium, from 90 to 10% tellurium dioxide and from 1 to 30% inert dielectric polymer. The igniter has a safe current of 1 A at a pulse power of 1 W for 5 minutes. The disadvantage is the use of a highly toxic deficient component of the igniter composition - tellurium oxide (TeO ₂ ). The disadvantages also include the use of the composition in bulk and high energy activation, which is almost not provided with a group explosion.

 Closest to the claimed EV for ED are EV according to OST 84-1380-76 (Schukin Yu.G., Lyutikov G.G., Pozdnyakov Z.G. "Means of initiation of industrial explosives", M., "Nedra", 1996, p.51 ) both with elastic fastening of the EV-E glow bridge, and with a rigid fastening of the EV-Zh glow bridge. EV consists of an igniter composition deposited on an incandescent bridge (nichrome, 30 μm), the igniter head on the surface is covered with a conductive composition based on iron oxide in a nitro-varnish. At both ends, the bridge is connected to the output wires passing (without insulation) through a plug made of polyethylene with conductive additives. The plug is inserted into the open end of the ED. In the case of rigid fastening of the incandescent bridge (EV-G), a frame is used, to the output brass strips of which the incandescent bridge is soldered. The frame is enclosed together with output wires that are soldered or welded to the legs of the contact strips of the frame, in the same plug (semiconductor plug), as in the case of EV-E.

 The following composition is used as an igniter: Bertoletova salt - rhodanide lead (49.5: 49.5) with the addition of 1% lead minium or Bertoletova salt - rhodanide lead (50:47) with the addition of 3% lead chromate (Schukin Yu.G., Lyutikov GG, Pozdnyakov ZG "Means of initiation of industrial explosives", M., "Nedra", 1996, p.23). Before applying to the incandescent bridge, the composition is kneaded on a nitro-varnish and applied to the incandescent bridge by dipping, followed by drying and then applying a conductive coating to the ignition head.

 The disadvantage of this design of the EV for ED is the low safe current (0.2 A), which does not guarantee the safety of the product in operation. It should also be noted that this EV for ED has insufficient protection against charges of static electricity, high sensitivity to mechanical stresses, which is largely due to the use of a highly sensitive igniter composition.

 In addition, this EV in the design of the CD has a short transmission time.

 It is known (A.I. Lurie, "Electric Explosion of Charges" M., Nedra, 1973, p. 22) that increasing the transmission time or conductivity of an incandescent bridge is one of the ways to increase the reliability of group detonation. By the time of transmission of EV is understood the time from ignition to the ejection of the force of fire from the head of the igniter, and for instantaneous ED - until the explosion of ED.

 The aim of the present invention is the creation of EV for ED, providing an increase in the safe current of at least 1 A, an increase in transmission time (conductivity of the incandescent bridge), increased protection of the ED with this EV from static charges and a decrease in sensitivity to mechanical and thermal effects of the ignition head of the EV. The proposed EM in the design of ED must, in addition, ensure reliable operation of successive groups of ED, reliably operate from domestic explosive machines, the manufacture of EM must be carried out on existing technological lines of production in Russia.

The real goal is achieved by the fact that molybdenum is used as an incandescent bridge (with a diameter of 30 microns) in the EV, and the composition of the following formulation is used as an igniter: potassium perchlorate - 40-80%; boron (amorphous) - 10-30%; additional oxidizing agent - 10-30%; binders - 1.5-2.5% in excess of 100%, where the following compounds can be used as an additional oxidizing agent: lead dioxide (PbO ₂ ), lead minium (Pb ₃ O ₄ ), lead (II) oxide (PbO), lead chromate (PbCrO ₄ ), and for low-toxicity EVs that do not contain highly toxic lead compounds, bismuth oxide (Bi ₂ O ₃ ), barium chromate (BaCrO ₄ ), and copper oxide (CuO) can be used. The introduction of a particular oxidizing agent in the composition allows you to change the thermal sensitivity of the composition and the response time.

 As a binder, fluororubber (for example SKF-26), colloxylin, nitrile butadiene rubbers (for example SKN-18, SKN-40, SKN-26) and a mixture of nitrile butadiene rubber with colloxylin, for example SKN-40, can be used colloxylin with a ratio of 1: 1-1: 4. Solutions of nitrile butadiene rubbers with a high acrylonitrile content are compatible with nitrocellulose solutions at certain proportions depending on the acrylonitrile content in the rubber (Polymer blends. Edited by D. Paul and S. Newman, Mir Publishing House, M., 1981, vol. 1, p. 47).

 Comparative characteristics of the compositions for the claimed EV are presented in table 1.

From the data given in table 1 shows that the inventive composition (compositions) has a higher combustion temperature (T _m ) at the maximum reaction rate, volume of gaseous products, greater strength (f) and thermal stability (higher T _sp ), less sensitivity to mechanical stresses, especially to friction.

Table 2 shows the formulations of the igniter composition used in EV with a change in the percentage of ingredients. The EV, on the bridge of which the corresponding formulation composition is applied using the above binders, is operable and corresponds to a safe current value of I _b ≥1 A and an ignition pulse (K _in ) of 15 to 30 ms A ² in a wide range of changes in the percentage of ingredients given in Table .2. With a change in the percentage of ingredients, the response time of the EV changes from 3 to 8 ms.

= 0,11 Ом•мм²/м). Он имеет высокую температуру плавления (Т_пл= 2620^oС), что обеспечивает большее время токопроводности (живучести) мостика накаливания. Заявляемый ЭВ с молибденовым мостиком накаливания, на который нанесен указанный выше воспламенительный состав, обеспечивает безопасный ток (I_б) 1,0 А, импульс воспламенения (К_в) составляет 16-25 мс • А², тогда как импульс плавления (К_пл) составляет более 35-40 мс • А², что обеспечивает высокую надежность срабатывания ЭВ в группе.The choice of molybdenum as an incandescent bridge provides the most favorable ratio between the value of the safe current and the ignition pulse. These ratios can be obtained when other pure metals are also used as an incandescent bridge: platinum, tantalum, tungsten. However, platinum and tantalum are very scarce and expensive metals, as for tungsten, its disadvantage is fragility, brittleness, and a decrease in its strength after heating. Therefore, molybdenum is the most optimal metal for incandescent bridges with a low specific resistance (ρ ₂₀ = 0.057 Ohm • mm ² / m) and a rather high temperature dependence (

= 0.11 Ohm • mm ² / m). It has a high melting point (T _PL = 2620 ^o C), which provides a longer conductivity (survivability) of the incandescent bridge. The inventive EV with a molybdenum filament bridge, to which the above ignition composition is applied, provides a safe current (I _b ) of 1.0 A, the ignition pulse (K _in ) is 16-25 ms • A ² , while the melting pulse (K _pl ) is more than 35-40 ms • А ² , which ensures high reliability of the EM operation in the group.

 Table 3 shows the main characteristics of the claimed EV and prototype.

 As can be seen from table 3, the inventive EV has a safe current of 1 A, increased transmission time (more than 3 ms), reduced sensitivity of the EV head to mechanical stresses, as well as a reduced sensitivity of the electric igniter head to thermal influences, which is associated with a higher heat resistance of the igniter composition (see table 1). In the table. Figure 3 also presents an EV with a molybdenum incandescent bridge with a diameter of 30 μm, on which the standard composition is applied (Bertoletova salt - rodanic lead - lead red lead). This EV does not provide a safe current of 1 A, the transmission time at the level of a standard EV. In addition, this EV is highly sensitive to mechanical stress (shock).

 Group undermining of the ED with the claimed EV was carried out with a serial connection of ED (type ED-3-N) from an explosive machine KVP-2/200 with a resistance of 10 ohms at the maximum length of the output conductors of the ED (length of conductors L = 2700 ÷ 4350 mm).

 The number of products of group detonation was at least 220 pcs., Which corresponds to the number of products, ceteris paribus, simultaneously undermined with a standard electric igniter (prototype).

 The ED with the proposed EV reliably withstands the effects of an electrostatic discharge of 25 kV voltage, both between the head and any of the wires, and with a direct discharge to the incandescent bridge through a 0.5 kΩ resistor. The inclusion of a resistor in the discharge circuit ensures safety at a discharge voltage of 25 kV from a 2500 pF capacitor.

Claims (3)

1. An electric igniter for an industrial electric detonator, comprising an incandescent bridge, an ignition composition, on which a conductive coating is applied, a rigid frame, lead wires, a plug of polymer material with conductive additives, characterized in that the composition of the following formulation is applied to the incandescent bridge,% :
Potassium Perchlorate - 40 - 80
Boron (amorphous) - 10 - 30
Additional oxidizing agent - 10 - 30
Binder in excess of 100% - 1.5 - 2.5
2. The electric igniter according to claim 1, characterized in that the following compounds can be used as an additional oxidizing agent: lead dioxide, lead minium, lead chromate, barium chromate, bismuth oxide, lead oxide.  3. An electric igniter according to claims 1 and 2, characterized in that fluorine rubber, colloxylin, nitrile butadiene rubber, a mixture of nitrile butadiene rubber with nitrocellulose or colloxylin can be used as a binder.  4. The electric igniter according to claims 1 to 3, characterized in that molybdenum is used as the material of the incandescent bridge.

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