Note: Descriptions are shown in the official language in which they were submitted.
~3S~ ~
- 1 - C-I-L 632A
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
-
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- 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,
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- 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.
EXAMPLES 1-8
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
- 5 - C-I-L 632
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,
.
~ ~q35~
- 6 - C-I-L 632
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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- 7 - C-I-L 632
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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- 8 - C-I-L 632
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 (%)
3022 2934 3104 170 1 24
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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9 - C-I-L 632
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.
EXAMPLE 11
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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10 - C-I-L 632
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.
- ~ :
~ 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
- - 12 - C-I-L 632
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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- 13 - C-I-L 632
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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- 14 - C-I-L 632
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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.
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- 15 - C-I-L 632
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 (%)
7454 7329 7565 236 0-99
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
... ..... ~
,
"`
. ~
:
: .
, `
- 16 - C-I-L 632
~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.
EXAMPLE 28
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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- 17 - C-I - L 632
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~
- 18 - C-I-L 632
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
.
.
' 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.
:,
19 -- C--I--L 632
~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
.
' '~' ,:
:.
.
s~
- 20 - C-I-L 632
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.
EXAMPLE 33
; 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.
51~
_ 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
.
,
