Downline wire

Patent metadata

Field	Value
Publication number	US-11456089-B2
Application number	US-201816618330-A
Country	US
Kind code	B2
Filing date	May 23, 2018
Priority date	May 23, 2017
Publication date	Sep 27, 2022
Grant date	Sep 27, 2022

Abstract

A downline wire (10) serves to connect a location on the ground surface to at least one detonator (52) in a blast hole. The downline wire includes at least two flexible electrical conductors (12, 14) encased by respective flexible layers of an insulating material (20, 22) and a flexible sheath (24) in which the insulated conductors are embedded. Each conductor (12, 14) is made of a copper-clad steel core and the insulating material is either a filled flexible polyvinylchloride (PVC) composition or a polyester elastomer. The sheath (24) is made from a medium or high density polyethylene compound which includes carbon black.

First claim

What is claimed is:

1. A downline wire for connecting a location on surface to at least one detonator in a blast hole, the downline wire including at least two flexible electrical conductors, a respective flexible layer of an insulating material which encases each conductor, and a flexible sheath in which the insulated conductors are embedded, wherein each conductor comprises a steel core which is clad with copper, the insulating material is selected from a filled flexible polyvinylchloride (PVC) composition and a polyester elastomer, and the sheath is made from a medium or high density polyethylene compound which includes carbon black.

2. A downline wire according to claim 1 wherein the PVC composition has a density of from 1.3 g/cm 3 to 1.4 g/cm 3 , an “A” Shore hardness of from 93 A to 103 A, and an elongation of from 280% to 325%.

3. A downline wire according to claim 2 wherein the density is 1.35 g/cm 3 , the “A” Shore hardness is 98 A, the unaged tensile strength at breakage is from 131 N/mm 2 to 145 N/mm 2 and the elongation is from 295% to 310%.

4. A downline wire according to claim 1 wherein the polyester elastomer has a tensile strength at breakage of from 296 N/mm 2 to 365 N/mm 2 , an elongation at breakage of from 330% to 370% and a nominal “D” Shore hardness of from 77 D to 87 D.

5. A downline wire according to claim 1 wherein the tensile strength of the wire at breakage is 331 N/mm 2 , the elongation at breakage is 350%, and the hardness is 82 D.

6. A downline wire according to claim 1 wherein the diameter of the steel core is from 0.5 mm to 0.7 mm and the steel has a tensile strength of from 373 N/mm 2 to 569 N/mm 2 , an elongation at breakage of from 18% to 30% and a resistance of from 240 to 280 ohm/km.

7. A downline wire according to claim 1 wherein the sheath has an outer profile comprising two opposed substantially parallel and flat sides, a first semi-circular edge between respective first ends of the flat sides, and a second semi-circular edge between respective second ends of the flat sides.

8. A detonation system comprising:
a detonator to provide a charge to ignite an explosive; and
a downline wire to connect the detonator to a surface location, the downline wire comprising:
two conductors;
a flexible thermoplastic insulator encasing the two conductors; and
a polyethylene sheath encasing the flexible thermoplastic insulator and the two conductors wherein the polyethylene sheath comprises a medium density polyethylene compound filled with carbon black (2.5%).

9. The system of claim 8 wherein each of the two conductors comprise a steel core and copper cladding.

10. The system of claim 9 , wherein the steel core has a tensile strength from 373 N/mm 2 to 569 N/mm 2 , and an elongation at breakage from 18% to 30%.

11. The system of claim 9 , wherein the steel core has a diameter from 0.5 mm to 0.7 mm.

12. The system of claim 8 , wherein the flexible thermoplastic insulator is a filled flexible polyvinylchloride composition.

13. The system of claim 12 , wherein the flexible thermoplastic insulator has an unaged tensile strength at breakage from 117 N/mm 2 to 159 N/mm 2 , and an elongation at breakage from 280% to 310%.

14. The system of claim 8 , wherein the flexible thermoplastic insulator is a polyester elastomer.

15. The system of claim 14 , wherein the flexible thermoplastic insulator has an unaged tensile strength at breakage from 296 N/mm 2 to 365 N/mm 2 , and an elongation at breakage from 330% to 370%.

16. The system of claim 8 , wherein the polyethylene sheath has an unaged tensile strength at breakage of 29.4 N/mm 2 , and an elongation at breakage of 800%.

17. A method for loading a blast hole comprising:
connecting a booster and a detonator to a downline wire, the downline wire comprising:
two conductors with a tensile strength from 373 N/mm 2 to 569 N/mm 2 , and an elongation at breakage from 18% to 30%,
a flexible thermoplastic insulator encasing the two conductors, and
a sheath encasing the flexible layer and the two conductors, the sheath comprising a polyethylene compound wherein the polyethylene sheath comprises a polyethylene compound filled with carbon black;
placing the booster and the detonator in a blast hole; and
filling the blast hole with an explosive material comprising an emulsion, a mixture, or both where the detonator experiences a dynamic force that causes the downline wire to elongate while the blast hole is being filled, and when a static force is exerted by the explosive material on the downline wire.

18. The method of claim 17 , wherein the downline wire has a tensile strength from 400N to 470N, and an elongation of 24% to 30%.

19. The method of claim 18 , wherein the elongation of the downline wire allows the downline wire to stretch between 24% to 30%.

20. The method of claim 18 , wherein the tensile strength of the downline wire allows the downline wire to resist a static force of up to 470N.

21. The method of claim 17 , further comprising determining a rate of charge to limit the dynamic force based on the diameter of the blast hole.

22. The method of claim 17 , wherein the flexible thermoplastic insulator comprises one of a filled flexible polyvinylchloride composition or a polyester elastomer.

23. The method of claim 17 , wherein the explosive mixture comprises ANFO.

24. A method of manufacturing a downline wire for an explosive detonation system, the method comprising:
providing two copper-clad steel cores;
encasing each of the two copper-clad steel cores in a flexible thermoplastic insulator to form separate insulated conductors; and
encasing both of the separate insulated conductors in a polyethylene sheath wherein the polyethylene sheath comprises a polyethylene compound filled with carbon black.

25. The method of claim 24 , wherein the flexible thermoplastic insulator comprises a filled flexible polyvinylchloride composition.

26. The method of claim 24 , wherein the flexible thermoplastic insulator comprises a polyester elastomer.

27. The method of claim 24 , wherein the polyethylene sheath has a density of 0.95 g/cc.

Assignees

• Detnet South Africa Pty Ltd

Inventors

• Olwage Phillip

Classifications

• F42D1/045 Primary

  Arrangements for electric ignition (dynamo-electric generators H02K) · CPC title

• F42D3/04

  for rock blasting · CPC title

• F42D1/24

  characterised by the tamping material · CPC title

• F42D3/06

  for seismic purposes · CPC title

• H01B7/0869

  comprising one or more armouring, tensile- or compression-resistant elements · CPC title