CA2048735A1 - Low energy fuse - Google Patents
Low energy fuseInfo
- Publication number
- CA2048735A1 CA2048735A1 CA 2048735 CA2048735A CA2048735A1 CA 2048735 A1 CA2048735 A1 CA 2048735A1 CA 2048735 CA2048735 CA 2048735 CA 2048735 A CA2048735 A CA 2048735A CA 2048735 A1 CA2048735 A1 CA 2048735A1
- Authority
- CA
- Canada
- Prior art keywords
- low energy
- tubing
- fuse
- energy fuse
- electric low
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Abstract
Abstract of the Disclosure Low Energy Fuse A non-electric low energy fuse comprises plastics tubing within which there is provided a core loading of mixed particles which are reactive or detonable to provide signal transmission means wherein the plastics tubing is an extruded tubing and has dispersed therein discrete extrusion flow-orientated units of a melt incompatible material in sufficient concentration and aspect ratio to present a barrier to the penetration of hot oil and thereby effectively enhance the oil resistance of the fuse.
Description
8~35 LOW ENERGY FUSE
This invention relates to non-electric low-energy fuses, that is to say, transmission devices in the form of elongate plastics tubing housing reactive or detonable particulate substances at a core loading sufficiently low for there to be no cross-initiation of a similar tube placed alongside (or lateral direct initiation of a surrounding commercial emulsion blasting explosive) when such a device is fired. Ordinarily the core material detonates but in some types rapid deflagration or pyrotechnic reaction suffices as when the tubing i5 connected to a detonator within which a deflagration to detonation transaction occurs. The signal transmission tubing is itself initiated by an electric cap, a non-electric detonator, an electric discharge device or indeed by any other means capable of initiating the required self-sustaining reaction or detonation of the core material. A favoured type of low energy fuse is the so-called shock tube or signal tube as described in, and cross-referenced in, European Patent Specification No 327219 (ICI). Another distinct class of low-energy fuse is that described in US Patent Specification No 4290366 (Atlas Powder Company). The contents of these prior Specifications and their references are incorporated by reference herein, in their entirety.
The mining, quarrying and construction industries who are the principal users of commercial explosives and accessories and are continually extending the frontiers of their operations into new situations that challenge the reliability of current accessories. Of present relevance is 2 ~ 3 ~
the trend towards increasing use of emulsion explosives and ANF0 and heavy ANFO blasting agents, the deployment of non-electric low-energy fuse initiation down-hole as well as on the surface as inter-hole link-ups, coupled with long sleep times (that is the periods of time when the fuse is in contact with the explosive before firing). Commonly the hydrocarbon fuel phase of such explosives is an oil or a petroleum fraction such as diesel, and invariably the plastics from which transmission tubes have been formed have been wholly or mainly of polyethylene (e.g. LLDPE) or a related (co)polymer in which the back-bone chain is a polyethylene and the chain carries side substituents which may be hydrocarbyl or functional groups such as carboxyl and its salt and ester derivatives (e.g, 'Surlyns'). All such pol~mers are prone to ingress of hydrocarbons of the explosive's fuel oil phase when in prolonged contact therewith. This is so to a greater or lesser extent depending upon the nature of those hydrocarbons, the _ chemical and physical structure of the polymer of the transmission tubing, and the temperature of the fuel phase (as when an emulsion explosive is loaded hot). Even surface transmission tubing may be in prolonged contact with oil where there is spillage of emulsion explosive or engine oils, and this too may become hot in many of the inhospitable environments in which blasting operations take place.
The Applicants have contrived mis-fires of non-electric transmission devices of the types above-described attributable to penetration of deleterious amounts of 3 ~
hydrocarbons into the interior core of the transmission tubing after prolonged contact.
This invention provides an improved plastics transmission tubing for use as a low-energy fuse wherein the starting plastics material is equivalent to any of the currently used plastics which are susceptible to oil penetration over an extended period of time of being in contact therewith e.g. wholly or predominantly made from addition polymers such as a polyolefin or derivatised polyolefin of the kinds hereinbefore described or another oil absorbing plastics material e.g a condensation polymer such as polyamide or polyester, and which contains in its central core a detonable signal transmitting particulate material (such a~ loose, consolidated, bound and/or thread/filament carried material) wherein the plastics tubing is an extruded tubing but is modified such that it has dispersed therein discrete flow orientated units of a melt incompatible material in sufficient concentration and aspect ratio to present a barrier to the ingress of hot fuel, such as diesel, and thereby effectively enhance the oil resistance of the fuse.
The dispersed units are preferably in the form of platelets or flakes to act as an effective barrier and mitigate the effect of penetrating hot fuel to thereby extend the sleep time of the transmission tubing.
Although flow orientated as the tube is formed, the barrier units will be randomly dispersed and will be advantageously up to about 1 mm across. The optimum dispersed proportion of barrier units is determined by ~ ~8 ~3~
experimentation having regard to the sleep time required.
To date, 1 to 5% w/w of PTFE flakes have been found to give suitable results. These results also suggest that other melt incompatible polymer or copolymer flakes or platelets wi]l also be useful. Thus the invention also provides a method of manufacturing a signal transmission tubing for use as a low energy fuse, the method comprising extruding a plastics tubing from a melt wherein discrete units of a melt incompatible material are dispersed to provide tubing having a random distribution of flow-oriented units therein to thereby enhance the oil resistance of the fuse.
According to a further aspect of the invention there is provided a method of extending the operational life of a transmission tubing for use as a low energy fuse which will be in contact with hot fuel oil such as diesel, the method comprising forming a transmission tubing of which the plastics material is wholly or predominantly a polyolefin or a derivatised polyolefin of the kinds above described (but may also be another oil absorbing plastic such as polyamide or polyester) and which contains in its central core a reactive signal transmitting particulate substance (such as loose, consolidated, bound or thread/filament carried material), wherein discrete units of a melt incompatible material are dispersed within the tubing during forming thereof to present a barrier to the ingress of hot fuel.
This modification has been shown to be capable of giving a substantially extended operational life to the transmission tube.
2~87~
In an example of the invention, a polyethylene transmission tube was constructed as follows.
A blend of 85% linear low density polyethylene (LLDPE) and 15% low functionality (2%) ethylene-vinyl acetate (EVA) to which about 1% w/w of polytetrafluoroethylene (PTFE) flakes of about 1 mm across were added was extruded by a Battenfelder extruder (5.0 cm diameter, 24:1 l/d metering screw), throuqh a 3.0 cm outer die and a 1.4 cm inner mandrel to form a transmission tubing having the flakes of PTFE randomly dispersed throughout. The melt was subjected to a 15:1 drawdown over 25 cm through a 7.6 mm diameter sizing die and processed as known per se in the art. The large tube dimensions were about 7.6 mm outer diameter (O.D.) extruded at a rate of about 5 m per minute. After stretching, the tube size was about 3 mm O.D. and produced at a rate of 45 m per minute. A reactive/detonable core mixture comprising explosive powder (HMX/A1) was added to the large tube at a rate sufficient to give a final core load of about 20 mgLm (4 4 g/m2 of internal area). The tensile strength of this tube was about 140 N/m2. A break load of 80 kg was required at an extension of 160%. The finished tubing was then immersed in hot diesel at 50C and after more than 100 hours the transmission tube was successfully detonated.
The mixed particles which are reactive or detonable to provide for signal transmission may be selected from a variety of reagents known per se in the field of pyrotechnics and would include oxidisers such as perchlorates, permanganates and peroxides; secondary high 2~73~
explosives such as PETN, RDX, HMX, TNT, dinitroethylurea;
and tetryl and metal/quasi metal fuels such as aluminium and silicon.
It will be appreciated that the core loading will be variable depending on the sleep time field conditions, and strength required but typically it will be in the range of 15 to 25 mgm~1.
Of course the temperature (and therefore penetration) of the fuel used in the field will vary considerably (from say 25C to 70C) and therefore this should be borne in mind when constructing a low energy fuse of the invention which must have a specified minimum sleep time.
The invention also extends to low-energy fuse assemblies comprising delay elements and/or detonators connected to one or both ends of the transmission tubing as described hereinbefore.
This invention relates to non-electric low-energy fuses, that is to say, transmission devices in the form of elongate plastics tubing housing reactive or detonable particulate substances at a core loading sufficiently low for there to be no cross-initiation of a similar tube placed alongside (or lateral direct initiation of a surrounding commercial emulsion blasting explosive) when such a device is fired. Ordinarily the core material detonates but in some types rapid deflagration or pyrotechnic reaction suffices as when the tubing i5 connected to a detonator within which a deflagration to detonation transaction occurs. The signal transmission tubing is itself initiated by an electric cap, a non-electric detonator, an electric discharge device or indeed by any other means capable of initiating the required self-sustaining reaction or detonation of the core material. A favoured type of low energy fuse is the so-called shock tube or signal tube as described in, and cross-referenced in, European Patent Specification No 327219 (ICI). Another distinct class of low-energy fuse is that described in US Patent Specification No 4290366 (Atlas Powder Company). The contents of these prior Specifications and their references are incorporated by reference herein, in their entirety.
The mining, quarrying and construction industries who are the principal users of commercial explosives and accessories and are continually extending the frontiers of their operations into new situations that challenge the reliability of current accessories. Of present relevance is 2 ~ 3 ~
the trend towards increasing use of emulsion explosives and ANF0 and heavy ANFO blasting agents, the deployment of non-electric low-energy fuse initiation down-hole as well as on the surface as inter-hole link-ups, coupled with long sleep times (that is the periods of time when the fuse is in contact with the explosive before firing). Commonly the hydrocarbon fuel phase of such explosives is an oil or a petroleum fraction such as diesel, and invariably the plastics from which transmission tubes have been formed have been wholly or mainly of polyethylene (e.g. LLDPE) or a related (co)polymer in which the back-bone chain is a polyethylene and the chain carries side substituents which may be hydrocarbyl or functional groups such as carboxyl and its salt and ester derivatives (e.g, 'Surlyns'). All such pol~mers are prone to ingress of hydrocarbons of the explosive's fuel oil phase when in prolonged contact therewith. This is so to a greater or lesser extent depending upon the nature of those hydrocarbons, the _ chemical and physical structure of the polymer of the transmission tubing, and the temperature of the fuel phase (as when an emulsion explosive is loaded hot). Even surface transmission tubing may be in prolonged contact with oil where there is spillage of emulsion explosive or engine oils, and this too may become hot in many of the inhospitable environments in which blasting operations take place.
The Applicants have contrived mis-fires of non-electric transmission devices of the types above-described attributable to penetration of deleterious amounts of 3 ~
hydrocarbons into the interior core of the transmission tubing after prolonged contact.
This invention provides an improved plastics transmission tubing for use as a low-energy fuse wherein the starting plastics material is equivalent to any of the currently used plastics which are susceptible to oil penetration over an extended period of time of being in contact therewith e.g. wholly or predominantly made from addition polymers such as a polyolefin or derivatised polyolefin of the kinds hereinbefore described or another oil absorbing plastics material e.g a condensation polymer such as polyamide or polyester, and which contains in its central core a detonable signal transmitting particulate material (such a~ loose, consolidated, bound and/or thread/filament carried material) wherein the plastics tubing is an extruded tubing but is modified such that it has dispersed therein discrete flow orientated units of a melt incompatible material in sufficient concentration and aspect ratio to present a barrier to the ingress of hot fuel, such as diesel, and thereby effectively enhance the oil resistance of the fuse.
The dispersed units are preferably in the form of platelets or flakes to act as an effective barrier and mitigate the effect of penetrating hot fuel to thereby extend the sleep time of the transmission tubing.
Although flow orientated as the tube is formed, the barrier units will be randomly dispersed and will be advantageously up to about 1 mm across. The optimum dispersed proportion of barrier units is determined by ~ ~8 ~3~
experimentation having regard to the sleep time required.
To date, 1 to 5% w/w of PTFE flakes have been found to give suitable results. These results also suggest that other melt incompatible polymer or copolymer flakes or platelets wi]l also be useful. Thus the invention also provides a method of manufacturing a signal transmission tubing for use as a low energy fuse, the method comprising extruding a plastics tubing from a melt wherein discrete units of a melt incompatible material are dispersed to provide tubing having a random distribution of flow-oriented units therein to thereby enhance the oil resistance of the fuse.
According to a further aspect of the invention there is provided a method of extending the operational life of a transmission tubing for use as a low energy fuse which will be in contact with hot fuel oil such as diesel, the method comprising forming a transmission tubing of which the plastics material is wholly or predominantly a polyolefin or a derivatised polyolefin of the kinds above described (but may also be another oil absorbing plastic such as polyamide or polyester) and which contains in its central core a reactive signal transmitting particulate substance (such as loose, consolidated, bound or thread/filament carried material), wherein discrete units of a melt incompatible material are dispersed within the tubing during forming thereof to present a barrier to the ingress of hot fuel.
This modification has been shown to be capable of giving a substantially extended operational life to the transmission tube.
2~87~
In an example of the invention, a polyethylene transmission tube was constructed as follows.
A blend of 85% linear low density polyethylene (LLDPE) and 15% low functionality (2%) ethylene-vinyl acetate (EVA) to which about 1% w/w of polytetrafluoroethylene (PTFE) flakes of about 1 mm across were added was extruded by a Battenfelder extruder (5.0 cm diameter, 24:1 l/d metering screw), throuqh a 3.0 cm outer die and a 1.4 cm inner mandrel to form a transmission tubing having the flakes of PTFE randomly dispersed throughout. The melt was subjected to a 15:1 drawdown over 25 cm through a 7.6 mm diameter sizing die and processed as known per se in the art. The large tube dimensions were about 7.6 mm outer diameter (O.D.) extruded at a rate of about 5 m per minute. After stretching, the tube size was about 3 mm O.D. and produced at a rate of 45 m per minute. A reactive/detonable core mixture comprising explosive powder (HMX/A1) was added to the large tube at a rate sufficient to give a final core load of about 20 mgLm (4 4 g/m2 of internal area). The tensile strength of this tube was about 140 N/m2. A break load of 80 kg was required at an extension of 160%. The finished tubing was then immersed in hot diesel at 50C and after more than 100 hours the transmission tube was successfully detonated.
The mixed particles which are reactive or detonable to provide for signal transmission may be selected from a variety of reagents known per se in the field of pyrotechnics and would include oxidisers such as perchlorates, permanganates and peroxides; secondary high 2~73~
explosives such as PETN, RDX, HMX, TNT, dinitroethylurea;
and tetryl and metal/quasi metal fuels such as aluminium and silicon.
It will be appreciated that the core loading will be variable depending on the sleep time field conditions, and strength required but typically it will be in the range of 15 to 25 mgm~1.
Of course the temperature (and therefore penetration) of the fuel used in the field will vary considerably (from say 25C to 70C) and therefore this should be borne in mind when constructing a low energy fuse of the invention which must have a specified minimum sleep time.
The invention also extends to low-energy fuse assemblies comprising delay elements and/or detonators connected to one or both ends of the transmission tubing as described hereinbefore.
Claims (14)
1. A non-electric low energy fuse formed from plastics tubing having a core loading of mixed particles which are reactive or detonable to provide for signal transmission wherein the plastics tubing is an extruded tubing and has dispersed therein discrete flow-orientated units of a melt incompatible material in sufficient concentration and aspect ratio to present a barrier to the ingress of hot oil and thereby effectively enhance the oil resistance of the fuse.
2. The non-electric low energy fuse of claim 1 wherein the units are in the form of platelets or flakes.
3. The non-electric low energy fuse of claim 1 or claim 2 wherein the content of flakes is from about 1 to 5% w/w.
4. The non-electric low energy fuse of claim 1 or claim 2 or claim 3 wherein the units are made from a plastics material differing from that from which the tubing is extruded.
5. The non-electric low energy fuse of claim 4 wherein the plastics material from which the units are made is polytetrafluoroethylene (PTFE).
6. The non-electric low energy fuse of claim 5 wherein the plastics tubing is extruded from a polymer selected from the group consisting of addition polymers and copolymers thereof other than PTFE.
7. The non-electric low energy fuse of claim 6 wherein the plastics tubing comprises a polymer selected from the group consisting of polyolefin(s), branched polyolefin(s), polyolefin(s) having functional group side substituents and derivatives thereof, and copolymers thereof.
8. The non-electric low energy fuse of claim 1 or claim 2 or claim 3 wherein the plastics tubing is made from a polymer selected from the group consisting of condensation polymers and copolymers thereof.
9. The non-electric low energy fuse of claim 8 wherein the plastics tubing comprises a polymer selected from the group consisting of polyamides, polyesters and copolymers thereof.
10. The non-electric low energy fuse of claim 1 wherein the form of the core loading is selected from the group consisting of loose, consolidated, bound and thread/filament carried material.
11. The non-electric low energy fuse of claim 10 wherein the amount of core loading is from 15 to 25 mgm-1.
12. A non-electric low energy fuse formed from an extrudable blend of about 85% linear low density polyethylene and about 15% ethylene vinyl acetate copolymer to which about 1% w/w of PTFE flakes of about 1 mm across were added prior to extrusion to form a tubular wall having extrusion flow-oriented flakes of PTFE randomly dispersed throughout said wall and within which there is confined a core loading of about 20 mg/m of a reactive/detonable mixture comprising HMX explosive and aluminium particles.
13. In a method of manufacturing a signal transmission tubing for use as a low energy fuse, the method comprising extruding a plastics tubing from a melt and providing a core loading of mixed particles which are reactive or detonable to provide a signal transmission medium the improvement consisting of adding discrete units of a melt incompatible material to the melt prior to extrusion to provide extruded tubing having a random distribution of extrusion flow-oriented units therein to thereby enhance the oil resistance of the fuse.
14. A method of extending the operational life of a signal transmission tubing for use as a low energy fuse in contact with hot fuel oil, the method comprising forming a plastics tubing having a core loading of a reactive particulate substance for use in signal transmission wherein discrete units of a melt incompatible material are dispersed within the extruded plastics tubing during forming thereof to thereby enhance the oil resistance of the fuse.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB909017717A GB9017717D0 (en) | 1990-08-13 | 1990-08-13 | Low energy fuse |
| GB9017717.1 | 1990-08-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2048735A1 true CA2048735A1 (en) | 1992-02-14 |
Family
ID=10680581
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2048735 Abandoned CA2048735A1 (en) | 1990-08-13 | 1991-08-08 | Low energy fuse |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU638156B2 (en) |
| CA (1) | CA2048735A1 (en) |
| GB (2) | GB9017717D0 (en) |
| ZA (1) | ZA916199B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9108753D0 (en) * | 1991-04-24 | 1991-06-12 | Ici Plc | Low energy fuse |
| CA2065780C (en) * | 1991-05-01 | 2002-11-26 | Robert C. Greenhorn | Shock tubing |
-
1990
- 1990-08-13 GB GB909017717A patent/GB9017717D0/en active Pending
-
1991
- 1991-08-02 GB GB919116783A patent/GB9116783D0/en active Pending
- 1991-08-06 ZA ZA916199A patent/ZA916199B/en unknown
- 1991-08-06 AU AU81604/91A patent/AU638156B2/en not_active Ceased
- 1991-08-08 CA CA 2048735 patent/CA2048735A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| GB9017717D0 (en) | 1990-09-26 |
| AU8160491A (en) | 1992-02-20 |
| GB9116783D0 (en) | 1991-09-18 |
| ZA916199B (en) | 1993-04-28 |
| AU638156B2 (en) | 1993-06-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |