Patent Application
20170074625
The present invention relates generally to apparatuses, primer units, systems and methods for electronic blasting, e.g., systems for initiation of buried explosives in applications including surface mining, underground mining, quarrying, civil construction, and/or seismic exploration on land or in the ocean.
In blasting applications, e.g., surface mining, underground mining, quarrying, civil construction, and/or seismic exploration on land or in the ocean, explosives are buried, e.g., in boreholes in selected patterns. To initiate the buried explosives, various initiation apparatuses are used, e.g., detonating cord (also known as “det cord”), or electrically controlled detonators. The timing of the blasts of the explosives in different locations in a blasting pattern can be critical to the success of a blasting operation.
In some environments and complicated applications, it may be undesirable to connect buried explosives with physical connectors, e.g., det cord or electrical cables. For example, such connectors can cause problems if they are strung across a mining site.
Wireless communication with electronic detonators has been proposed, but existing systems remain inappropriate for some applications. For example, some proposed wireless systems using radio-frequency (RF) signals require a line-of-sight connection from a blasting machine to the collar of each borehole. Furthermore, being able to activate electronic detonators with wireless signals may make storing, transporting and deploying such detonators extremely dangerous if blasting signals are received and interpreted at the wrong time, or incorrectly interpreted.
A first class of wireless electronic blasting systems may employ conventional radio wave communications to and from the borehole. In these systems, the receiver or transceiver at each borehole has at least an antenna outside the borehole to communicate, since radio waves may not travel through rock or even through stemming material. A secondary communication channel may be needed between the “top box” and the in-hole device in which the timing is done and which, at the correct time, will cause initiation of the explosives train in the borehole.
A second class of wireless electronic blasting systems may employ through-the-rock wireless communication, in which communication is effected via generation over the blast pattern of a controlled magnetic field that is detected by magnetometers which are part of the initiation devices within each borehole.
Initiation that relies on radio communication to (and optionally from) each borehole has the disadvantage of requiring access by the radio waves to the receiver at the collar of the borehole at blasting time. Since line-of-sight communication is generally much more reliable, it is generally much preferred to reliance on wave reflection or refraction for communication at blasting time. In underground mining in particular, preservation of line-of-sight communication from the firing transmitter to each receiver at the borehole collar is sometimes difficult and may be impossible (for example due to unsafe ground conditions). Through-the-rock communication—which may be referred to as “through-the-earth” (TTE) communication—may be advantageous in allowing blasting to proceed when access to the collars of the holes to be blasted may not be convenient, or safe, or even possible.
The through-rock wireless systems that have been described include a detonator. In these systems, the magnetically-transmitted commands are received by the receiver devices in each borehole. The receiver device then sends an appropriate command to an electric or electronic detonator, which functions as the first element in a conventional explosives train. A disadvantage of this system is inclusion of the detonator which must either be factory or field assembled with the receiver device. Detonators generally contain primary explosives which are more sensitive to electromagnetic interference (EMI), heat, friction, spark and impact, in both manufacture and use, than secondary explosives. For example, a fusehead may pick up an electromagnetic (EM) signal as it generally has poor EM protection, even if electronic portions of a detonator are EM protected. Detonators may require special handling, transportation and storage, which adds to the inconvenience and cost of using detonators as essential components.
Laser initiation systems for blasting may use a laser outside a borehole, and an optical fibre for guiding energy to an explosive in the borehole, or a diode laser included with control electronics connected into the borehole; however, existing laser systems require electrical or optical connections from the initiating device out of the borehole, and are thus prone to failure in some applications, e.g., where the material surrounding the initiating device moves before firing (e.g., due to other earlier blasts in the same area), and may contribute undesirable wire or cable waste in a blasting site.
There is a need, at least in some applications, to simplify electronic blasting systems and to improve their safety.
It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative.
In accordance with the present invention, there is provided an initiator apparatus (IA) for blasting, the apparatus including:
a magnetic receiver for receiving a magnetic communication signal through the ground by detection of a magnetic field;
a controller, in electrical communication with the magnetic receiver, for processing the magnetic communication signal to determine a command for blasting; and
a light source in electrical communication with the controller for generating a light beam to initiate a light-sensitive explosive (LSE) in accordance with the command.
The present invention also provides an explosive primer unit including:
the IA described hereinbefore;
an explosive apparatus with LSE coupled to the IA; and
a booster explosive around the LSE.
The present invention also provides a blasting system, including:
a plurality of initiator apparatuses, each being the IA described hereinbefore;
a blast controller for generating the command; and
a magnetic transmitting system in electrical communication with the blast controller for receiving the command, and configured to generate the magnetic communication signal representing the command.
The present invention also provides a method of blasting, the method including the steps of:
receiving a magnetic communication signal through the ground by detection of a quasi-static magnetic field;
processing the magnetic communication signal to determine a command for blasting; and
generating a light beam to initiate a light-sensitive explosive (LSE) in accordance with the command.
The present invention also provides an initiator apparatus (IA) for blasting, the apparatus including:
a magnetic receiver for receiving a magnetic communication signal through the ground by detection of a magnetic field;
a controller, in electrical communication with the magnetic receiver, for processing the magnetic communication signal to determine a command for blasting; and
an electro-mechanical interface to control a light source, based on electrical communication from the controller, to generate a light beam to initiate a light-sensitive explosive (LSE) in accordance with the command.
The present invention also provides an initiator apparatus (IA) for blasting, the apparatus including:
a controller component for controlling the IA to follow a command for blasting; and
optical coupling for coupling the controller component to an encoder for communicating with the encoder prior to the blasting.
Preferred embodiments of the present invention are hereinafter described, by way of example only, with reference to the accompanying drawings, in which:
Described herein is a blasting system providing through-rock wireless initiation and in-hole light initiation (or photo-initiation) of a light-sensitive explosive. The described blasting system permits use of initiating apparatuses with electronics packages that contain no explosive, and are thus safer than detonators, and the like, which include explosives. The initiating apparatus need not be manufactured in a licensed explosives factory, and may be manufactured, transported and stored not as hazardous materials but as any other electronic apparatus. There is thus no need to attach long leg wires to the initiating apparatus: adding long leg wires to existing wireless detonators may add to their complexity and cost of manufacture, transport and storage. The described blasting system does not require wired connections from the buried initiating apparatus. The described blasting system does not require access to a collar of a borehole in which the initiating apparatus is buried at blasting time. The initiating apparatus can be controlled to initiate with a programmable timing based on in-hole delay, which can provide a controlled burning front during blasting. The described blasting system may require no detonator and no primary explosive.
A blasting system 100, as shown in
The system 100 includes a magnetic transmitting system 106 configured to send signals to the initiating apparatuses 200 through the ground 102. Through-ground wireless communication (which can be referred to as through-the-earth (TTE) communication; or through-rock wireless communication for ground comprising mostly rock) includes communication by wireless signal transmission along wireless through-ground signal paths 118 through the ground 102, through the bulk explosive 116, through the primer unit 300 and into the IA 200.
The through-ground wireless communication is provided by the system 100 between the transmitting system 106 and the initiating apparatuses 200 in their respective holes 104. For example, at the time of firing, the system 100 can provide one-way communication from the transmitting system 106 and each initiating apparatus 200 (or each selected initiating apparatus 200) in its hole 104 to initiate the initiating apparatus 200 and thus a blast.
The system 100 may include an encoder unit 112 (e.g., a hand-held computer equipped with a suitable interface) to program the initiating apparatuses 200 before deployment into the holes 104. Suitable interfaces may include a Universal Serial Bus (USB) cable, RS232 cable, optical coupling, short-range RF coupling, etc. . . . .
The magnetic transmitting system 106 (also referred to as a “transmitter”) can include a signal generator 108 that is configured to send a modulated current into a low-resistance conductive loop or coil 110. The coil 110 can include a coil with one or more turns of a conductor capable of carrying a large modulated electrical current, e.g., 50 amps.
The transmitting system 106 is configured to provide a selected transmit range and a selected field strength for magnetic communication signals generated by the transmitting system 106. The transmit range is selected based on application conditions, e.g.: (i) a planned size of a blast using the IAs 200; (ii) a predetermined sensitivity of the IAs 200; and (iii) ambient magnetic noise in an environment in and around the system 100 (i.e., ambient magnetic noise in the micro-Tesla or higher range that would be detected by the IAs 200 in the holes 104). The strength of the magnetic field generated can be controlled based on a diameter and a number of the turns of the coils in the coil 110, and an amplitude of the current flowing through the coils. The number of the turns in the coil of the transmitting coil 110 may be small, and may be one. The current amplitude may be tens to hundreds of amps, e.g., between 10 Amps (A) and 1000 A. The coil diameter may be tens to hundreds of meters e.g., between 10 metres (m) and 1000 m. The coil 110 may comprise a plurality of separate coils supplied from one shared current source and the signal generator 108: in such a multi-coil arrangement, the coils are arranged and configured such that the generated magnetic fields of the coils are additive, while each coil is small enough to be portable by a person, e.g., for placement by a person. The plurality of coils may have diameters between 0.1 m and 10 m.
Frequencies in the modulated electrical current in the coil 110, and thus frequencies in the generated magnetic field, may be in a range from 20 Hertz (Hz) to 2500 Hz.
The signal generator 108 includes one or more electronic modulation components (e.g., circuits, modules, processors, and/or computer-readable memory) configured to modulate signals for transmission by the magnetic field. The electronic modulation components may provide modulation based on Frequency-Shift Keying (FSK), Pulse Width Modulation (PWM), Amplitude Modulation (AM), and/or Frequency Modulation (FM).
The provided modulation is selected based on the type of a magnetic receiver 204 in the IA 200. If the magnetic receiver 204 includes one or more inductive sensors, the modulation includes an alternating current (AC) or oscillating carrier to induce current in the magnetic receiver 204. If the magnetic receiver 204 includes one or more magnetometers, the modulation is quasi-static modulation to allow detection of quasi-static components of the generated magnetic field.
The transmitting system 106 may include an electrical power source including a mains power connection, fuel-powered generators, and/or a supply battery e.g., commercially available generators or arrays of lead-acid batteries.
The transmitting system 106 may include a blast controller 109 (which may be referred to as a “blaster” or “blasting machine”) for controlling the signal generator 108. The blast controller 109 may be configured to generate blasting commands for the signal generator 108 to send to the IA 200. The blast controller 109 may include a commercially available computing device (e.g., a personal computer) and blasting software.
The transmitting system 106 may include a user interface (UI) for operation of the system 100. The UI may include a front panel on a box housing the signal generator 108. The UI may include a hand-held device in electronic communication (e.g., using a conductive wire, or optical communications, or short- or long-range radio-frequency transmitters and receivers) with the signal generator 108.
The transmitting system 106 may be placed as close to the blast as is practical to minimise distances through the ground between the transmitting system 106 and the IAs 200. In some embodiments, at close proximity to the blast, the box may be afforded protection, including a protective housing, for example a steel enclosure.
The coil 110 may be made to be disposable, allowing it to be placed very close to, or even amongst or surrounding, the holes 104. The coil 110 may be configured to be disposable by forming the coil 110 using low-cost conductive members, e.g., with insulation designed for a single use. A coil 110 placed very close to the holes 104 may require less transmitting power, and thus less current-carrying capacity, so higher-impedance conductive members could be used in the coil 110. By at least partially destroying or damaging the coil 110 during the blast, e.g., due to heating of the conductive members and/impact from the blasting, the possibility of commands being erroneously transmitted to undesirably unexploded IAs 200 is reduced.
The initiating apparatus (IA) 200, as shown in
The initiating apparatus (IA) 200, as shown in
The switch 214 may be a commercially available switch, e.g., a MOSFET device.
The light source 215 and electronic components 202 to 214 in the IA 200 are electrically connected by electrical conductors 218, e.g., conductive wires or conductive tracks on at least one printed circuit board.
The initiating apparatus 200 may be an integrated device with the components forming a unit inside the housing 216, as shown in
The magnetic receiver 204 includes one or more magnetic field sensors. The magnetic receiver 204 may be a magneto-inductive receiver with one or more magneto-inductive sensors, e.g., commercially available magneto-inductive receivers. The magnetic receiver 204 may be a quasi-static magnetic field sensor, or magnetometer, including one or more magnetometer sensors, e.g. commercially available magneto-resistive devices. The magneto-inductive devices may be coils of fine wire with a ferrite core. Such devices, when customised for the fields being generated (e.g., particular field strengths) may generally be more sensitive than magneto resistive devices. The magnetic receiver 204 may include electronic amplifiers having low noise and very high gain for amplifying electrical signals from the magnetic field sensors, e.g., including commercially available operational amplifiers. The receiver component 204, including the magnetic sensors, the amplifiers and one or more signal processors, can, for example, receive (i.e., detect with an acceptable signal-to-noise ratio) an oscillating magnetic field intensity of the order of about 100 nano-Teslas or less; in embodiments, the range can be about 1 nano-Tesla or less.
The IA controller 206 may be a digital signal processor (DSP) based on a commercially available DSP configured for demodulating and decoding the amplified electrical signal from the magnetic receiver 204. One or more programmable logic controllers (PLCs) or application-specific integrated circuits (ASICs) may be programmed to interpret the incoming signals as commands, and can initiate an appropriate sequence of events for each command. The IA controller 206 may include a state machine with the following statuses: a power-saving mode, an active listening mode, an armed mode, a charging mode, and a firing mode.
The following incoming commands can control the controller component 206 to perform the following tasks:
The timer 212 is configured to have a coefficient of variation that is equal to or less than about 0.1%, and preferably equal to less than 0.01%. The timing delay is configured to have a time delay that is selectable with a precision of about 1 ms. The timer 212 may be a commercially available timing component, e.g., a crystal oscillator.
The IA 200 may be programmed onsite by the encoder 112. The encoder 112 may be a hand-held device that is easily carried by a user and is suitably rugged for mining conditions. In embodiments, the encoder 112 may send instructions to the controller component 206 without any acknowledge or other back-signal from the controller component 206. In other preferred embodiments, two-way communication can occur between the encoder 112 and the controller component 206. The channel for such communication can be a wire or optical devices connected to the controller component 206 that temporarily connects to the encoder 112, a short range wireless connection such as BlueTooth®, a terminal on the outside of the controller component 206 that mates with a terminal on the encoder 112, or an optical coupling between the controller component 206 and the encoder 112. In order for this optical channel to be established, both the encoder 112 and the controller component 206 can be equipped with a light-emitting diode (LED) and a photocell, e.g., commercially available LED and photocell connected to and controlled by the IA controller 206. In embodiments, the optical channel can avoid having external electrical terminals on the IA 200, which could corrode in a harsh chemical environment, e.g., in mining applications. An example encoder may be based on a commercial hand-held computer (e.g., the Trimble NOMAD™) fitted with an external adapter that contains optical communications equipment, and the hand-held computer provides the user interface.
Encoding of each IA 200 can occur before deployment into the hole 104. Each IA 200 may be uniquely associated with its hole 104, or there may be more than one, sometimes up to ten, IAs 200 per hole 104. The encoder 112 sends to the controller component 206 its delay time (in milliseconds) and optionally its GID, and recovers from the controller component 206 its individual (factory-programmed) ID and optionally a condition report.
Since the IA 200 alone contains no explosive, the operation using the encoder 112 is safe provided that the user can not be subjected to an accidental pulse (or pulses) of light of harmful intensity and/or duration, e.g., if the IA 200 is defective. Having an IA 200 with no explosive allows full-power testing of the IA 200, including measuring the light beam power and/or duration from the light source 215.
Once encoding is complete with the encoder 112, the IA 200 is coupled, using a coupling, to a booster containing the light-sensitive explosive (e.g., in a capsule) to form the primer unit 300 (which may be referred to as the “primer”). The coupling includes means to keep the surfaces forming the optical interface clean, and provide a seal that is substantially impervious to the environment in the hole (e.g., as a minimum, the seal may withstand hydrostatic pressure of about 10 bar). This primer unit 300 may be deployed into the hole 104. For vertical boreholes, deployment is preferably via a tether so that free-fall of the primer unit 300 is avoided.
As shown in
Example light-sensitive explosives in the capsule 302 may be pentaerythritol tetranitrate (PETN) containing carbon black or another secondary explosives such as Research Department Explosive (RDX) or octagon or High Melting Explosive (HMX). Carbon black may be an effective dopant at a level of 2% to 5% to render the PETN more sensitive to light; the absorption of the visible and infrared light and its conversion to heat ignites the PETN. Detonation may occur via a deflagration-to-detonation transition (DDT), which may proceed more effectively under conditions of strong confinement. The amount and type of light-sensitive explosive initiated is sufficient to initiate an explosives train in a column of commercial explosives, and thus initiate a blast at the location of the initiating apparatus 200. In experiments, the run-up time to full detonation has been found to be less than 100 microseconds without sealing of the distal end of the PETN column.
The capsule 302 may include a hollow confining container, e.g., a short metal tube. The internal diameter of the tube may be in the range of 2 millimetres (mm) to 5 mm, and preferably about 3 mm. The length of the tube is selected based on the explosive that the PETN is required to initiate. For example, the PETN tube can be embedded in a commercial booster, e.g., including Pentolite (Pentolite may include about 40 to 60% TNT, the balance being PETN), and a 50/50 Pentolite blend may be preferred. The length of the pressed PETN column in the tube may be in the range of 10 to 20 mm to adequately initiate the Pentolite that surrounds it intimately.
The surface or volume of the LSE, e.g., at a proximal end of a doped PETN column that is configured to be illuminated by the light source 215, can be sealed for the purpose of efficient DDT by window 306 and seals 308. The window 306 is transparent to the wavelengths of light from the light source 215 e.g., quartz or sapphire can be used for the dual purpose of sealing and allowing the passage of the light pulse. A spherical sapphire lens may be used as a sealing window 306, e.g., with a diameter of about 2.5 mm. The window 306 is preferably extremely strong, resisting the pressure of the DDT event, and has excellent optical properties (e.g., high transmission, low absorption and low distortion of visible and infrared light). The window 306 can be attached in or to the proximal end of the capsule 302 or the IA 200 by providing a precision machined surface of a shape corresponding to the shape of the spherical lens, and optionally providing a thin gasket between the metal tube and the window (e.g., the spherical lens). The window 306 may include an optical lens or lens system, selected for transparency and the wavelengths of the optical source 215, that focuses (or defocuses) the light beam into a selected volume of the LSE (e.g., selected depth and diameter). The window 306 may include two co-operative windows, one in the IA 200 and the other in the capsule 302 that provides the window 306 when the capsule 302 is coupled to an IA 200. The window 306 and the connector 304 and the seal 308 form a coupling for connecting the IA 200 to the capsule 302.
In an embodiment, the light source 215 may not be an integral component of the housing 216, but may be housed within the booster explosive 310, in intimate association with window 306 and capsule 302. In this embodiment, connection of the IA 200 with the booster to form the primer 300 involves forming an electrical rather than an optical connection between the two components of primer 300: i.e., in this embodiment, the IA 200 may include electronic drivers for the light source 215, but not the light source 25 itself, until the IA 200 is assembled to form the primer 300. In this embodiment, IA 200 includes an electro-mechanical interface to control the light source 215, based on electrical communication from the IA controller 206, to generate the light beam to initiate the light-sensitive explosive (LSE) in accordance with command for blasting. The light source 215 and the electronic portions of the IA 200 are electrically and mechanically coupled using the electro-mechanical interface. The electro-mechanical interface includes electrical and mechanical components on the IA 200 that provide equivalent connections to those between the light source 215 and the switch 214. The electro-mechanical interface on the IA 200 may include connectors (electrical pins and plugs, and a bayonet or screw thread), and the light source 215 (in its own housing) may include corresponding connectors (corresponding to the electrical pins and plugs, and a bayonet or screw thread). The electro-mechanical interface for coupling to the light source may include a seal to be dust and/or water resistance, or proof. The seal may be a cover through which the connectors extend.
In seismic exploration applications, the LSE charge may initiate an explosive (e.g., Pentolite) to generate signals (shock waves) for analysis to determine geological characteristics in the search for oil and gas deposits.
In alternative embodiments, the booster may include or be replaced by a detonation cord that can then be connected to other boosters in a conventional manner.
The system 100 may provide a method 400 of, or for, blasting, including the following steps, as shown in
Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
The present application is related to U.S. Provisional Application No. 61/971,205, filed on 27 Mar. 2014 in the name of Orica International Pte Ltd, the entire specification of which is hereby incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2015/050122 | 3/23/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61971205 | Mar 2014 | US |
