CA1200718A

CA1200718A - Reinforced explosive shock tube

Info

Publication number: CA1200718A
Application number: CA000438483A
Authority: CA
Inventors: James R. Simon; David J. Welburn
Original assignee: Individual
Current assignee: Orica Explosives Technology Pty Ltd
Priority date: 1983-10-06
Filing date: 1983-10-06
Publication date: 1986-02-18
Also published as: ZA846710B; NO160507C; NO844002L; NO160507B; AU3235884A; AU560237B2; SE8404957L; SE8404957D0

Abstract

Abstract Reinforced Explosive Shock Tube Low energy explosive shock tubing is provided which consists of a two-ply, inner and outer layer plastic tube having a plurality of lengthwise textile filaments bonded into the interface between the plastic layers. The textile filaments are chosen for their low elongation properties and the resultant shock tube resists stretching especially in warm borehole environments.

Description

'7:1~

~ L ~ L 6~3 The present invention relates to low energy eæplosi.~e ~hock tubiny of the NONE~ ~Reg~ TM) type. In particularr the invention rela~es to an explosive shock tube ha~in~
improved resistance to stretch and break especially in a hot borehole environment.
Explosive shock tubing as disclosed in Canadian Patent No. 878,056 granted August 10, 1971 is now widely kno~l and used in the blasting art~ This shock tubing or detonating fuse consLsts of small diameter~ for example~ 5 millimetre~
outside diameter tubing of a pliable plastic~ such as polyvinyl chloride, polyethylene, SURLYN (Reg~ TMl or the like having an inner diameter of about 3 millimetres. The i5 inner walls of the tubing has adhered thereto a thin layer of powdered explosive or reactive material, such as PET~
(pentaerythritol tetranitrate), HMX (cyclotetramethylene-tetranitramine) or powdered metal mixtures with ~hese When initiated at one end by means of an appropriate device such as a detonating cap, a percussion or impact wave i5 propagated within and along the tubing tQ` activate a blastin~
cap attached at the remote end of the tubins~ Explosive shock tubing may be employed in most instances as a replacement for conventional detonating cord in non-electric blasting and has the advantage of low noise, safe handling and low cost.
A modified type of low energy explosive shock tuhe~
having a sandwich-type construction of two different plastic i~, ,, ~ .

- 2 C-I-L 663 materials, is disclosed in Canadian Patent No. 1,149,229 granted July 5, 1983. This type o~ tubing is designed t~
withstand mechanical stress.
Both the single ply and double p]y (sandwich) plas~ic shock tubing is susceptible to elongation and possible breakage particularly when used in boreholes containins warm or hot explosives, for-example, water gel or slurry compositions~ Elongation can also occur in surface blasting operations, quarrying and the like where the tubing is ~0 stressed after exposure to the sun's heat particularly in tropical climatesO Elongation has the effect of $hi~ning ou~
or dislodging the film of reactive material coated on the inner tube surface which action may lead to the malunctio~ng of the shock tube as an energy conveyor. In particular, where a booster charge attached to a length of shock tubing is suspended in borehole filled with a hot (65C) explosive mixture, stretching of the tubing inevitably occurs and, occasionally, the tube is stretched to the breaking poi~t It has now been found ~hat stretching of explosi~e snock tubing can be eliminated by providing a tube consisting ol a sandwich~type construction comprising inner and outer ~u~e layers, the inner layer having high adhesion properties for a thin layer of powdered energy-pxoducing material distri~uted on its inner surface and the outer layer having high resistance to mechanical damage, and a plurality of lenst.hwise textile filaments of low elongation properties bonded at ~he interface of the inner and ou~er tube layers.
The accompany~ng drawing, in which Figure 1 is a perspective view of the end portion or a reinforced shock tube; and Figure 2 is a cross-section of the tube of Figure 1 will provide a fuller understanding of ~he invention.
With re~erence to the drawing where like numerals are used for like parts, there is shown a two~ply plastic ~U~?
consisting of an inner tub~ ply 2 and an outer tube ply 3~

1~()0~

~ 3 - C-I-L 663 At the interface between plies 2 and 3 and bonded thereto ~re lengthw.ise textile filaments 4. Coated on. the inner walls of ply 2 is a powdered energy generating material 5.
The plastic comprising inner tube ply 2 is one which has good adhesion prop~rties for the powdered energy generating material 5. SURLYN (Reg. TM) ~ a salt-containin~
polyethylene ionomer, has been found to be particularly suitable. The plastic of the outer tube ply 3 is chosen ~or its resistance to mechanical damage and a polyethylene having a densit~ of about 0.93 g/cm3 is ideally suited for this purpose~ Other suitable plastics for the outer tube axe~
polypropylenet polyvinyl chloride, polyamide and polyurethane.
The textile filaments 4 are selected from those filaments o~
cords which show substantially no e].ongation under longitudinal stress even at temperatures of the or~er of 65C. Particularly useful are hi~h tenacity, low elonsation filaments made from viscose rayonl polyami.de, polyesterr polypropylene and polytetrafluoroethylene~
The --number of textile filaments 4 employed will depend on the fineness or denier of the strand. From the point of view of convenience of manufacture and suitable bonding of filaments 4 to tube plies 2 and 3, filaments having a denier of between about 500 and 2000 are preferred. Typic~lly ~5 between about 5 and 10 of such filaments are evenly distributed around and within the tubular sandwich~
The reinforced tubing of the invention is conveniently manufactured by an overextrusion process wherein.. ~he in~er plastic tube ply 2 is extruded in a tube extrusion apparatus and the textile filaments are linear].y applied or laid around the outer surface of the extruded tube. The ilamented inner tube is then passed throu~h a second extrusion apparatus where an overcoating of a second plastic is applied as tube ply 3. The filament~. are r thus, enveloped between and bonded to tube plies 2 and 3.

1?~1718 ~ 4 - C-I-L 663 EX~MPLE
A series of explosi.ve shock tubes havins variou~
constructions were prepared and subjected to tensile stren~th tests at 22C~ and 65~Cc The tests involved subjèctin~ thle shock tubes to stretch to the breaking point by the force of applied weight. The results are given in the Table below.

TABLE

Tbbing Type ' ~ 'ral VA~n~_~ ~ypi~l Usa~e or Mas~ Dimen~ior _ ~ per ~th (g/~(mm) _ Single tube 100~ S~LYN (~eg.~M) 4.8 ~.9 1,4 __~ ~ _ ~_ Sandwich tube Inner ply: SURLYN 4.8 (unreinforced) Outer ply: Poly- 2~7 3,~
ethylene __ ~ ~ ~
Textile ~ein Inner ply: SURLYN 4~8 forced Tube I Tex~iles: 5 #1100 .
. denier .
rayon 0.6 3~g 1~4 Outer ply: Poly- ~
_ _ ethylene _ ~ . ~ _ _ _ .

Textile Rein- Inner ply: SU~LYN 4.8 forced Iube II Textiles: 10 #llQO .
denier .
rayon 1.2 3~9 1.4 Outer ply: Poly-ethylene 2.7 l __ _ _ _ _ e ... __ ~._. _ -- ~ ., .

TABLE Cont'd ~ ___________ _ . ~___ , ................ . .. _~
Tubing type Typical Construction Tensile Strength Tensile 5tre~gt~
(k~) Reduct~on over Temp~rature I ~2C 65CRange 22C t3 65C

Sin~le tube--- 100% SUgLYN 7.3 2~7 63~
_ .
Sandw~-c~-tub~ Inner ply. SURL~N 10.0 3.2 68%
(unreinforced) Outer ply: Po~y~ 68%
ethyle~e _ _ _ __ --__ _ ~ , Te~tile Rein- Inner ply~ SU~LYN .
forced Tube I Textiles: 5 #1100 : denier 29.0 18.4 37 r~yon Outer ply: Poly-~
ethylene .

. ______ ~
~ _ ___ ___ lextile Rein~ Inner ply: SURLYN
~orced Tube II Textiles~ 10 ~1100 . deniex . 38.5 29~9 22~, rayon Outer ply: Poly-. _ _ _ethylene . . _ ~ 6 ~ C-I-L 663 FrQm the results in the Table, it can be seen that the fibre rein~orced tubing showed a su~stantial improvement in tensile strength over the non~reinforced tubing.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A low energy explosive shock tube comprising a bonded, two-ply, inner and outer layer plastic tube, the inner layer having high adhesion properties for a thin layer of powdered energy-producing material distributed on its inner surface and the outer layer having high resistance to mechanical damage and a plurality of lengthwise textile filaments of low elongation properties bonded at the inter-face of the said inner and outer tube layers.

2. An explosive shock tube as claimed in Claim 1 wherein the said inner tube layer consists of a salt-containing polyethylene ionomer.

3. An explosive shock tube as claimed in Claim 1 wherein the said outer tube layer plastic is selected from polyethylene, polypropylene, polyvinyl chloride, polyamide and polyurethane.

4. An explosive shock tube as claimed in Claim 1 wherein the said textile filaments are selected from viscose rayon, polyamide, polyester and polytetrafluoroethylene.

5. An explosive shock tube as claimed in Claim 1 wherein the denier of the said textile filaments is from 500 to 2000.

6. An explosive shock tube as claimed in Claim 3 wherein the polyethylene has a density of 0.93 g/cm3.