CA1150514A - Delay composition for detonators - Google Patents

Abstract

Abstract C-I-L 632A
Delay Composition for Detonators An improved pryotechnic delay composition of inter-mediate to slow burning time is provided for use in both electric and non-electric blasting caps. The composition comprises a mixture of barium sulphate and silicon to which may optionally be added a proportion of red lead oxide.
The composition is characterized by the absence of any carcinogenic properties and is not water soluble.

Description

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Delay Composition for Detonators This invention relates to a novel pyrotechnic delay composition characterized by low toxicity, mois-ture resist-ance and uniform burn rate. In particular, the inventionrelates to a delay composition of intermediate to slow-burning time range for use in both non-electric and electric blasting caps.
This application is a division of Application Serial No. 366,968 filed December 17, 1980.
Delay detonators, both non-electric and electric, are widely employed in mining, quarrying and other blasting ope-; rations in order to permit sequential initation of the explosive charges in a pattern of boreholes. Delay or sequ-ential initiation of shotholes is effective in controlling the fragmentation and throw of the rock being blasted and, in addition, provides a reduction in ground vibration and in air blast noise.
Modern commercial delay detonators, whether non~electric or electric, comprise a metallic shell closed at one end which shell contains in sequence from the closed end a base charge of a detonating high explosive, such as for example, PETN and an above adjacent, primer charge of a heat-sensitive detonable material, such as for example, lead azide. Adjacent the heat-sensitive material is an amount of a deflagrating or burning composition of sufficient quantity to provide a desired delay time in the manner of a fuse. Above the -.` .

- 2 - C-I-L 632 delay composition is an ignition charge adapted to be ignited by an electrically heated bridge wire or, alter-natively, by the heat and flame of a low energy detonating cord or shock wave conductor retained in the open end of the metallic shell.
A large number of burning delay compositions comprising mixtures of fuels and oxidizers are known in the art. Many are substantially gasless compositions; that is, they burn 10 without evolving large amounts of gaseous by-products which would interfere with the functioning of the delay detonator.
In addition to an essential gasless requirement, delay com-positions are also required to be safe to handle, from both an explosive and health viewpoint, they must be resistant 15 to moisture and not deteriorate over periods of storage and hence change in burning characteristics, they must be simply compounded and economical to manufacture and they must be adaptable for use in a wide range of delay units within the limitations of space available inside a standard detonator 20 shell The numerous delay compositions of the prior art have met with varying degrees of success in use and application.
Some of the prior art compositions contain ingredients which are recognized as carcinogenic. Other compositions contain ingredients which are soluble in water which may lead to 2~ deterioration of the composition in a moist environment.
For example, one widely known delay composition comprising a mixture of powdered tungsten metal, particulate potassium perchlorate and barium chromate and diatomaceous earth, contains both water soluble material (potassium perchlorate) 30 and a carcinogen (barium chromate). Another known type of delay composition consists of a mixture of antimony and po-tassium permanganate or a mixture of zinc, antimony and po-tassium permanganate. These compositions, because they contain a water-soluble salt oxidizer, tend to deteriorate 35 in hot, moist storage or use environments. As a result, 353L~

- 3 - C-I-L 632 detonators containing such water-soluble materials must be constructed to positively exclude any moist atmosphere thus imposing problems in manufacture.
The present invention provides a pyrotechnic delay com-position of intermediate to slow burning time which composi-tion contains no recognized carcinogen or any water-soluble material, By "intermediate to slow burning time" is meant a burning time of from about 400 to about 3200 milliseconds 10 per centimeter of length.
In accordance with the invention, an improved pyrotechnic delay composition is provided for use in a delay blasting cap assembly which comprises from 45 to 70% by weight of barium sul-phate and from 30 to 55% by weight of silicon, The invention may be more cleaxly understood by refer-ence to the accompanying drawing which illustrates in Fig. 1 a non-electric delay detonator and in Fig. 2, an electric delay detonator, showing the posi-20 tion therein of the delay composition of the invention.
With reference to Fig. 1, 1 designates a metal tubularshell closed at its bottom end and having a base charge of explosive 2 pressed or cast therein. 3 represents a primer charge of heat-sensitive explosive. The delay charge or 25 composition of the invention is shown at 4 contained in drawn lead tube or carrier 5. Surmounting delay charge 4 i5 ignition charge 6 contained in carrier 7. Above ignition charge 6 is the end of a length of inserted low energy detonating cord 8 containing explosive core 9. Detonating cord 8 is held 30 centrally and securely in tube 1 by means of closure plug 10 and crimp 11. When detonating cord 8 is set off at its re-mote end (not shown) heat and flame ignites ignition charge 6, in turn, igniting delay composition 4. Composition 4 burns down to detonate primer 3 and base charge 2, With reference to Fig. 2, a tubular metal shell 20 ~ 4 ~ C-I L 632 closed at its bottom end is shown containing a base charge of explosive 21. A primer charge 22 is indented into the upper surface o~ charge 21, Above charge 21 and primer 22 and in contact therewith is delay composition 23 contained within a swaged and drawn lead tube or carrier 24. Spaced above delay charge 23 is a plastic cup 25 containing an ig-nition material charge 26, for example, a red lead/boron mixture. The upper end of shell 20 is closed b~ means of 10 plug 27 through which pass lead wires 28 joined at their lower ends by resistance wire 29 which is embedded in ignition charge 26. When current is applied to wire 29 through leads 28, charge 26 is ignited. Flame from ignited charge 26 ignites delay composition 23 which in turn sets off primer 22 15 and explosive 21.
The invention is illustrated with reference to several series of tests summarized in the following Examples and Tables.

A number of delay compositions were made by intimately mixing together different proportions of barium sulphate and powdered silicon. The specific surface area of barium sul-phate was 0.81 m2/g while the specific surface area of silicon was 8.40 m2/g. The mixtureswere prepared by vigorous mechanical 25 stirring of the ingredients in slurry form utilizing water as the liquid vehicle. After mixing, the slurry was filtered under vacuum and the resulting filter cake was dried and sieved' `~ to yield a reasonably free-flowing powder. Delay elements were made by loading lead tubes with these compositions, drawing 30 these tubes through a series of dies to a final diameter of about 6.5 mm and cutting the resultant rod into elements of length 25.4 mm. The delay times of these elements, when as-sembled into non-electric detonators initiated b~v NONE~ (Reg.
TM) shock wave conductor, were measured. Delay time data are 35 given in Table I below while the sensitivities of some of these compositions to friction, impact and electrostatic discharge are shown in Table II below, . T A B L E
_ _ _ _ _ _ _ _ _ _ _ .
Composition Length of Delay Number of Example BaS04:Sil) Element Detonators _ _ (mm) Tested _ _ 1 70 : 30 25.4 202) 2 64 : 36 25.4 2o2) 3 62 : 38 25.4 2o2)

4 60 : 40 25.4 2o2) 58 : 42 25.4 2o2) 6 56 : 44 25.4 202) 7 50 : 50 25.4 203) 8 45 : 55 25,4 202) T A B L E I Cont'd ____________ _ Delay Time (milliseconds) Example _ Mean Min. Max. Scatter Coefficient 4 of Variation ) . ( ) 1 3385 3224 3541 317 2,40 2 5062 4834 5184 350 1.77 3 5325 5172 5476 304 1.71 4 5681 5527 5786 259 1.36 5936 5839 6003 164 0.66 6 5642 5529 5765 236 0.98 7 5089 4966 5360 394 1.95 8 4466 4256 4856 600 2,99 _ ~otes: 1) BaSO4 specific surface area 0.81 m2/g;
Si specific surface area 8,40 m2/g.
2) Denotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon igniter element, .

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Delay times quoted include delay time contribu-tion of these two igniter elements, nominally 95 milliseconds.
3) Denotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a 6 35 mm long red lead-silicon-Ottawa sand (sio2 ) igniter element. Delay times quoted above include delay time contribution of these two igniter elements, nominally 160 milliseconds.
4) Delay time coefficient of variation is delay time standard deviation expressed as a percentage of mean delay time, T A B L E II
_ _ , Composition Impact2 Friction3) Electrosta)tic BaSO4:Sil) Discharqe4 , Min. Ignition Min. Igni- Min, Ignition Height tion Height Energy (cm) (cm) tmJ) .
70:30 >139.7 ~83.8 >256.5 65:35 >139.7 ~83.8 >256.5 60:40 ~139.7 ?83.8 ~256.5 55:45 ~139.7 ~83.8 >256.5 50:50 ~139.7 ~83.8 >256.5 45:55 ~139.7 ~83,8 ~256.5 _ _ ~otes: 1) BaSO4 specific surface area 0.81 m2/g;
Si specific surface area 8.40 m2/g.
2) In impact test, mass of fall-hammer (steel)

5.0 kg. Samples tested in copper/zinc (90/10) cup.
3) In friction test, mass of torpedo (with aluminum head) 2.898 kg. Samples tested on aluminum blocks.
4) Discharge from 570 pF capacitor.

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EX~MPLE 9 The relationship between means delay time and length o~
delay element was es~ablished for a barium sulphate-silicon 58:42 composition. Again, the tests were performed using non-electric detonators initiated by ~ONEL (Reg. TM). Results are shown in Table III below~
T A B L E III

10 Example Composition Length (L) of Number of Detonators BaSO4:Sil) Delay Element Tested (mm) 9 58:42 ) 126 735 202) ) 25.4 20 ) T A B L E III Cont'd _______________ Delay Time (milliseconds) Relation between _ Mean Delay Time Mean Min, Max. Scatter Coefficient of (T) and Delay Variation (%) Element Length _ 1449 1381 1515 134 2,26 ( T = 234.7 L -3022 2934 3104 170 1.24 ( 8.0 ms 5936 5839 6003 164 0.66 ( (Correlation ( coefficient ( O.g998) Notes: 1) BaSO4 specific surface area 0.81 m2/g;
Si specific surface area 8.40 m2/g.
2) Each detonator incorporated a 12.7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon igniter element. Delay times quoted include delay time contribution of these two igniter elements, nominally 95 milliseconds.
From the results shown in Table III, it can be seen that 35 a strong linear relationship exists between mean delay time and length of barium sulphate-silicon delay element. This characteristic is important in manufacturing processes that `''`

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5~4 utilize drawn lead delay elements, as it affords control of nominal delay times by simple manipulation of element cutting lengths.
EX~MPLE 10 A evaluation of the low-temperature timing performance of barium sulphate-silicon compositions was made by subjecting non-electric detonators containing a BaSO4-Si 58:42 pyro-technic mixture to a temperature of -45C for a period of 10 24 hours. The detonators were subsequently fired at that temperature ~y means of NONEL (Reg. TM) shock wa~e conductor and their delay times were noted. Timing results are given in Table IV below.
T A B L E IV
_____________ , _ Composition Test Number of Detonators Example BaSOg:Sil) Temperature Tested/Number Fired . _ ( ) ~,~
58:42 20 20/20'~
58:42 -45 15/152) T A B L E IV Cont'd _____________ Delay Time (milliseconds) % Change in % Change Delay Time in Delay Mean Min. Max. Scatter Coefficient t20C to Time/C
of Varia--45C) tion (%) 3138 3068 3218 150 1 48 3.84 0.059 .
Notes: 1) BaSO4 specific surface area 0.81 m~/g;
Si speci~ic surface area 8.40 m2/g.
30 2) Each detonator had a 12.7 mm long red lead-silicon igniter element, a 6.35 mm long red lead-silicon igniter element and a 6.35 mm `~ long barium sulphate-silicon delay element.
Delay times quoted include delay time contribu-tions of igniter elements, nominally 95 milli-seconds.

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As seen from the results in Table IV, the temperature coefficient of the BaS04:Si 5~:A2 composition ovex the temperature range -45C to +20C is 0.059 percent per degree C Also, it can be noted that no failure occurred in these low-tempexature firing tests.

In order to assess the effect of the specific surface area of silicon on the delay ~ime characteristics of barium 10 sulphate-silicon composition, three mixtures, each consisting of BaSO4-Si in the mass ratio 58:42, were prepared. Silicon samples of specific surface area 8.40, 7 20 and 6.05 m2/g were used in the preparation of the compositions under test The delay times of these compositions were measured in as-15 sembled NO~EL (Reg. TM) initiated non-electric detonators The results`which were obtained are summariæed in Table V, below, where it can be seen that as the fuel specific sur-face area is decreased the greater is the delay time of the composition T A B L E V
____________ Composition Specific Sur- ¦ Length of ~umber of Example BaS04:Sil) face Area of ¦ Delay Ele- Detonators Silicon ment (mm) Tested 11 58:42 8 40 25 4 Z0z) 58:42 ~.20 25.4 202 58:42 6.05 25 4 20 ) T A B L E V Cont'd ____________ .
Delay Time (milliseconds) Mean Min. Max. Scatter Coefficient of Variation ~ _ _ _ ~` 5936 5839 6003 164 0.66 6603 6453 6749 296 1.26 8065 7495 8351 856 2.6 . `

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Notes: l) BaSO4 specific surface area 0,81 m2/g.
2) Each detonator incorporated a 12,7 mm red lead-silicon igniter element and a 6.35 mm red lead-silicon igniter element. Delay times quoted include delay time contribution of these two igniter elements, nominally 95 milliseconds.
EXAl~PLE 12 The suitability for use in electric detonators of one 10 of the compositions of the invention was determined. The oxidant-fuel combination which was evaluated was 60:40 BaSO~-Si by mass. Barium sulphate of specific surface area 0.81 m2/g and silicon of specific surface area 8.40 m2/g were employed.
Electric detonators, each having a delay train consisting of 15 a 6.35 mm long red lead-silicon-Ottawa sand (Sio2) igniter element superimposed on a 25.4 mm long barium sulphate silicon delay element, were assembled and fired. Statistical data on the timing performance of these detonators is con-densed in Table VI. Included in Table VI, for comparison, 20 are the corresponding timing results obtained for the same mixture in non-electric, ~ONEL (Reg. TM) inidiated detonators.
T A B L E VI
_____________ Exam le Composit~n Detonator ¦ Length of Number of P BaSO4:Si Type Delay Ele- Detonators ~ 25 ment (mm) Tested .~ ..
12 60:40 Non-electri ~ 25.4 2o32) 60:40 Electric ¦ 25.4 20 ) T A B L E VI Cont'd _____________ Delay Time (milliseconds) , , 30 Mean Min. Max. Scatter Coefficient of Variation .. ... _ _ ~ (%) .__ .
5681 5527 5786 259 1.36 5075 4905 5173 268 1.33 . .
~otes: l) BaSO4 specific surface area 0.81 m2/g;
Si specific surface area 8.40 m2/g.

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~ C-I-L 632 2) ~enotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a

6.35 mm long red lead-silicon igniter element.
Delay times ~uoted include delay time contribu-tion of these two igniter elements, nominally 95 milliseconds.
3) Denotes detonators which incorporated a 6.35 mm long red lead-silicon-Ottawa sand (SiO2) igniter element. Delay times quoted include delay time contribution of this igniter element, nominally 85 milliQeconds.
The barium sulphate/silicon delay composition of the invention may in some cases, advantageously contain a propor-15 tion of red lead oxide. The inclusion of red lead oxide has the effect of somewhat speeding up the burning time of the composition without any adverse effect on either toxicity or water solubility. Typically, such a three-component composi-tion comprises from 15 to 60% by weight of barium sulphate, 20 from 25 to 75% by weight of red lead oxide and from 5 to 40%
by weight of silicon. While the two-component delay composition of the invention comprising barium sulphate/silicon mixture provides a burning time of from about 1300 to 3200 milli-seconds per centimeter of length, the three-component barium 25 sulphate/silicon/red lead oxide mixture provides a somewhat higher burn rate of from about 400 to 2750 milliseconds per centimeter of length.
The further aspect of the invention comprising the addition of red lead oxide to the barium sulphate/silicon 30 delay composition is illustrated with reference to several series of tests which are summarized in the following Examples and Tables.
EX~MPLES 13-19 A series of seven delay compositions comprising barium 35 sulphate/red lead oxide/silicon mixtures were compounded in which the silicon proportion was varied from 5.7 percen-t to 35.0 percent by weight of the total composition while the .

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~5~514 ratio of oxidants barium sulphate/red lead oxide was held constant at 0,80, The effect of these formulation changes on composition delay time was measured. In the formulations 5 the specific surface area of silicon was 1.79 m2/g; barium sulphate and red lead oxide had specific surface areas of 0.81 m2/g and 0.73 m2/g respectively. The mixtures were prepared by vigorous mechanical stirring of the ingredients in slurry form utilizing water as the liquid vehicle.
After mixing, the slurry was filtered under vacuum and the resulting filter cake was dried and sieved to yield a reasonably free-flowing powder. Delay elements were made by loading lead tubes with the compositions, drawing the lead tubes through a series of dies of decreasing diameter to a 15 final diameter of about 6.5 mm, and cutting the resultant rod into elements. Non-electric detonators initiated by means of ~ONEL (Reg. TM) shock wave conductor were loaded with the delay elements, fired and the delay times noted.
A summary of the delay times is yiven in ~able VII, below.
T A B L E VII
______________ ~E m le ~ Composition ;Length of Number of xa pBaS04: _(mm)_ fired i 25~ 1~ 41.9 : 52.4 : 5.7 ' 25,4 202) 14 ~41.5 : 51.8 : 6.7 1 25.4 202) lS l40.0 : ~0.0 : 10.0 1 25,4 1 203~
16 37.8 : 47.2 : 15.0 25.4 1 203) 1~ 35.6 : 44.4 : 20.0 1 25.~ ~ 203) 30` 18 31.1 : 38.9 : 30.0 i 25.~ j 203) 19 28.9 : 36.1 : 35.0 1 25.4 ~ 203) ~ , .
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TABLE VII ~nt'd Example ~ Delay time (milliseconds) Mean Min. ' Max. , Scatter I Coefficient of ~~ ! variation (%) t37034 6867 ' 7318 ~451 ' 1.56 145324 5186 , 5423 237 , 1.19 151779 ; 1739 ! 1815 76 1 1.18 16-- 1106 ~ 1078 1 1148 70 ,, 1.63 171365 ~ 1324 , 1418 94 1l 1.83 182541 1 2492 1 2593 101 1 1.13 194155 1 4010 1 4348 l,338 ~ 1.75 Notes: 1) Silicon of specific surface area 1.79 m2/g 2 ) Denotes detonators which incorporated a 12.7 mm long red lead-silicon ignlter element and a 6.35 mm long red lead-silicon igniter element.
Delay times quoted include delay time contribu-tion of these two igniter elements, nominally 95 milliseconds.
3) Denotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon-Ottawa sand (sio2) igniter element. Delay times quoted above include delay time contribution of these two igniter elements, nominally 160 milliseconds.
EX~MPhES Z0-27 In a series of eight tests, formulations comprising barium sulphate/red lead oxide/silicon mixturas were compounded in the same manner as described in Examples 13 19 in which the silicon proportion was held constant at 6.7 percent~by~weigXt 30 while the ratio of oxidants barium sulphate/red lead oxide ~ was varied from 0,26 to 0.90. Again, the specific surface ; areas of barium sulphate, red lead oxide and silicon were ` 0.81, 0.73 and 1.79 m2/g respectively. The delay time :,~

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characteristics of the compositions, tested in non-electric ~O~EL initiated detonators, are shown in Table VIII~ It should be noted that a control sample of composition containing no barium sulphate was included in these tests The performance . of this control sample, consisting of Pb304/Si in the ratio 93.3:6.7, is also shown in Table VIII.
The data shown in Table VIII demonstrate~ that in the case of BaSO4/Pb3o4/si compositions in which the proportion of 10 silicon is fixed, any increase in the proportion of barium sulphate (at the expense of red lead oxide) has the effect of retarding the delay time of the composition.

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TABLE VIII

Example Composition Length of INumber of ) delay elementidetonators ~BaSO4: Pb304: Sl tmm~ I fired ~44.2 : 49.1 : 6.7 25,4 1 102) 21 42.2 51.1 6.7 25.4 i 102) 22 40.7 : 52.6 : 6.7 25.4 1 203 23 ~ 37.2 56.1 6.7 ` 25.4 ! 203) 24 ` 34.2 : 59.1 : 6.7 ~ 25.4 i 203) 29.2 : 64.1 ~ 6.7 25.~ j 203) 26 24.2 : 69,1 : 6.7 25.4 ! 203) 27 19.2 74.1 : 6.7 25.4 1 203) - nil : 93.3 : 6.7 ,25.4 1 203) TABLE VIII cont'd Example Delay time (mi_llseconds) ! Mean Min. I Max. I Scatter ¦ Coefficients of , ~ I I variation (%) 20 2~ 6114 1 6019 6290 271 1 l.lg , '22 4941 1 4894 4988 I g4 1 0,50 23 ', 2844 ~, 2773 2916 143 1.59 24 ` 2132 ~ 2096 2169 73 1 0.82 ~5 j 1642 1 1621 1658 37 1 0.56 25 26 1393 1 1380 1416 36 ~ 0.62 ~, ~27 1202 1 1190 1211 21 1 0.45 - 449 j 406 473 67 1 4.60 ... ..... ~
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~otes: 1) Specific surface area of silicon 1079 m2/g .` 2 ) Denotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon-Ottawa sand (sio2) igniter element. Delay times quoted include delay time contribution of these two igniter elements, nominally 160 milliseconds.
3~ Denotes.detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon igniter element. Delay times ~uoted include delay time contribution of these two igniter elements, nominally 95 milliseconds.

The effect of the specific surface area of silicon on the mean delay time of barium sulphate-red lead oxide-silicon ` composition was assessed. The formulation selected was BaSO~/Pb304/Si in the ratio 44.2:49.1:6.7 respectively by 20 weight. Silicon samples of specific surface areas 1.79, 3.71 and 8.40 m2/g were used to make the compositions undar test. The results which were obtained are condensed in Table IX, where it can be seen that the mean delay time de-~` creases as silicon specific surface area is increased.

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TABLE IX
_ I Composition _ ISpecific Sur- I Length of Exam~le ~ face Area of Delay Element 5 ¦ BaSO4: Pb304: Sl Silicon (mm) I ) 4~.2: 49,1: 6.7 1 1,79 25,4 ! 28) 44,2: 49,1: 6,7 1 3.71 25,4 ' ) 44,2: 49,1: 6.7 j 8.40 25.4 _ TABLE IX Cont'd .
I ' ; Delay Time (milliseconds) lOi Example Number of !Detonators Mean Min. Max. Scatter Coefficient IFired , I I jof Variation ! ~ _ I) lolJ7454 1l 73297565 1236 i 0.99 28) 202)1535 ' 14921568 !76 1 1.24 ) 202)753 ~ 746 761 1~ 1 0.55 Notes: 1) Denotes detonators which incorporated 12. 7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon-ottawa sand (SiO2) igniter element. Delay times quoted include delay time contribution of these igniter elements, nominally 160 milliseconds.
) Denotes detonators which incorporated a 12. 7 mm long red lead-silicon igniter element and a 6.35 mm long red lead-silicon igniter element. Delay times quoted include delay time contribution of these igniter elements, nominally 95 milliseconds.
EX~MPLES 29 & 30 The relationshi~ betwsen mean delay time and delay element length were determined for two of the compositions of the in-30 vention namely BaSO4~ b304/Si in the ratio 29,2:64.1:6.7 and also in the ratio 41.5:51.8:6.7 by weight. Lead-drawn delay elements of lengths 6.35, 12.7, 25.4 and 50.~3 mm made with these compositions were assembled into non-electric, NONEL (Reg. TM) `` initiated detonators, subsequently fired and the delay times 35 noted. Results are shown in Table X. From these results : ~ 5~3s~

it can be seen that, for the two formulations tested, strong linear relationships exist between mean delay time and delay element length. This characteristic is impoxtant in manu-facturing processes which utilize lead-drawn delay elements, as it affords control of nominal delay times by simple mani-pulation of element cutting lengths TABLE X
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' Composition l)!Length of (L) ¦ ~umber of lO Example BaSO4: Pb304: Si !Delay Element I Detonators ! ~ (mm) I Fired ~ 29 l29.2 64.1:6.71 1265 45 20-) 15' ) 50.8 202 30 l41.5: 51.8: 6.7) 126 735 203 ; ) 25.4 20 i ) 50.8 203 ; 20 TABLE X Cont'd DelaY time (milliseconds) Relation xamp e Mean Min. Max. Scatter Coefficient I Between Mean of Variation Delay Time (T) I ' % ~ Length (L)of = 25 ! I ' ~ Delay Element 29 478 452, 502, 50 12.64 ) T(ms) = 62.17 i 859 1 844j 870 1 26 0.72 ) (L) + 74.4 ms ` 1646 l1629l1660 ¦ 31 0.57 ~ (Correlation co-1 3237 l3204 3267 ! 63 0 58 ) efficient ; 30` ' I 0.9999) 30 ,1134 ~1074 1243 169 3.51 ) T(ms) = 205.5 2602 ! 2402!2690 288 2.75 ) (L) - 33.1ms ` ~ i5392 l5178',5506 ¦ 328 1.57 ) (Correlation co-10317 !9896~10490 ! 594 1.49 ) efficient j , ! I 0 9993)_ _ ~otes: 1) Specific surface area of silicon 1.79 m2/g ~" 2 ) Denotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element. Delay times quoted include delay time contribution of this igniter element, nominally 70 milliseconds.

:, ~otes: 3 ) Denotes detonatoxs which incorporated a 12.7 mm long red lead-silicon igniter element and a 6,35 mm long red lead-silicon-ottawa sand (sio2) igniter element. Delay times quoted include delay time contribution of these two igniter elements, nominally 160 milliseconds.
EX~MPLES 31 and 32 An assessment of the low temperature timing perormance 10 and reliability of the BaS04/Pb304/Si compositions of the invention was made by subjecting non-electric detonators con-taining two of the above mentioned pyrotechnic mixtures to a temperature of -45C for a period of 24 hours, The detonators were subsequently fired at that temperature by means of ~O~EL
15 (Reg. TM) shock wave conductor and their delay times were noted.
Results are given in Table XI. It can be noted that no failure occurred in these low temperature firing tests, TABLE XI

1 ~ Composition l)~Length of , Test ~ ~umber of 20 Examp e~BaS04: Pb304SiIDelay Element temp. Detonators (mm) (C)_ Fired & Tested t 31 29.2: 64.1:6.7) 25.4 20 202)/202) ) 25,~4 _45 202 /202 32 41.5: 51.8:6.7) 25.4 20 203),~203) 25 j ) 25.4 _45 203)/203 _ _ TABLE XI Cont'd Exa~[~le I Delay time (milli~econds) .~ _ __ _, j Mean I Min.Max. ¦ Scatter Coefficient of l I I Variation (%) '` 301 31 16461629 1 1660 31 1 0.57 18361800 1 1875 75 1 1.10 32 53925178 1 5506 328 1 1.57 ` ! 71236752 1 7319 567 1 2.11 .
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TABLE XI Cont'd , Example% Change in Delay % Change in Delay time time/C
(20C to -45C) _ , 31 11.54 0.178 32 32.10 0.494 Notes: 1) Specific surface area of silicon 1.79 m2/g 2 ) Denotes detonators which incorporated a 12.7 mm `~ 10 long red lead-silicon igniter element. Delay times quoted include delay time contribution of this igniter element, nominally 70 milliseconds.
3) Denotes detonators which incorporated a 12.7 mm long red lead-silicon igniter element and a 6~35 mm long red lead-silicon-Ottawa sand (sio2 ) igniter `~ element. Delay times quoted include delay time contribution of these two igniter elements, nominally 160 milliseconds.

; 20 In order to demonstrate the suitability of the composition of the present invention for use in electric detonators, the timing performance in electric detonatoxs of a mixture of BaSO4/Pb3o4/si in the weight ratio 29.2:6401:6.7 was determined.
Results are shown in Table XII. Included in Table XII for com-25 parison, are the corresponding timing results obtained for the same mixture in non-electric, ~ONEL (Reg. TM) initiated detonators.

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_ 21 - C-I-L 632 TABLE XII

Example ! Composition Detonator Length ~umber of , BaSO4: Pb304: Sil) Type of Detonators~
Element Tested 29.2: 64.1: 6.7 ~on- 25.4 20Z) 33 ) electric ) 29.2: 64.1: 6.7 Electric2504 103) T~BLE XII Cont'd _ I Example Delay time (milliseconds) ¦ Mean ' Min. I Max. I Scatter I Coefficient of Variation (%) ) ~ 1642 1 1621 1 1658 1 37 0.56 15~ ) I 155911528!1584 1 56 1 1.07 _ I~otes: 1) Specific surface area of silicon 1.79 m2/g `', 2 ) Denotes detonators which incorporated a 12.7 rmn long red lead-silicon igniter element. Delay times quoted include delay time contribution of 2~ this igniter element, nominally 70 milliseconds.
3) ~O igniter element was used in electric detonators.
;The components of the novel delay composition of the invention must be in a finely divided state to in~ure intimate 25 con~act between the oxidants and fuel. Measured in terms of `?specific surfacè area, the barium sulphate ranges from 0.5 to 3.0 m2/g, preferably 0.8 to 2.7 m2/g, the red lead oxide ranges from 0.3 to 1.0 m2/g, preferably from 0.5 to 0.8 m~/g, and the silicon ranges from 1.4 to 10.1 m2/g, preferably from 30 1.8 to 8.5 m2/g. The oxidizers and fuel may advantageously be slurried with vigorous stirring in water as a carrier, the water removed by vacuum filtxation and the filter cake dried and sieved to yield a free-flowing, finepowder ready for use .

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Claims (2)

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

1. A pyrotechnic delay composition adapted for non-electric and electric delay detonators comprising from 15% to 60% by weight of particulate barium sulphate, from 5% to 40% by weight of particulate silicon and from 25% to 75%
by weight of particulate red lead oxide.

2. An improved delay blasting detonator having a delay composition interposed between an ignition element and a primer/detonation element, said delay composition comprising from 15% to 60% by weight of particulate barium sulphate, from 5% to 40% by weight of particulate silicon and from 25% to 75%
by weight of particulate red lead oxide.