U.S. patent number 3,683,809 [Application Number 05/051,053] was granted by the patent office on 1972-08-15 for detonator fuse initiated aqueous slurry explosive system.
This patent grant is currently assigned to Hercules Incorporated. Invention is credited to William C. Burkle.
United States Patent |
3,683,809 |
Burkle |
August 15, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
DETONATOR FUSE INITIATED AQUEOUS SLURRY EXPLOSIVE SYSTEM
Abstract
A detonator cord-initiated slurry type inorganic oxidizer salt
explosive system is provided, in which the slurry explosive charge
is detonatable without substantial loss in detonation energy
encountered heretofore, and which comprises a detonator cord having
alternate high and low energy loadings extending in lengthwise
contact with a mass of the explosive; a booster type detonator for
the explosive within the mass and adjacent each high energy core
section and detonatable by detonation energy transmitted from the
adjacent high energy section; each high energy section being
detonatable by detonation energy transmitted from an adjacent low
energy core section which has a loading not exceeding about 18
grains PETN (or equivalent) per foot, and thereby laterally
transmits insufficient detonation energy to the main charge to
cause substantial lowering of the detonation energy thereof. The
high energy section loading is at least 25 grains PETN (or
equivalent) per foot. In one embodiment, the high energy section
loading can be at least 200 grains PETN (or equivalent) per foot to
constitute an integral unit of high energy section and adjacent
booster without need for a separately disposed booster.
Inventors: |
Burkle; William C. (Sharpley,
Wilmington, DE) |
Assignee: |
Hercules Incorporated
(Wilmington, DE)
|
Family
ID: |
21969057 |
Appl.
No.: |
05/051,053 |
Filed: |
June 30, 1970 |
Current U.S.
Class: |
102/332 |
Current CPC
Class: |
F42D
1/06 (20130101) |
Current International
Class: |
F42D
1/00 (20060101); F42D 1/06 (20060101); F42d
001/04 () |
Field of
Search: |
;102/22-24,27
;149/42 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pendegrass; Verlin R.
Claims
What I claim and desire to protect by Letters Patent is:
1. A cap-insensitive aqueous slurry type inorganic oxidizer salt
explosive system including a detonator cord-booster type initiator
therefor, having improved detonation energy characteristics,
comprising a mass of said explosive and a detonator cord having
alternate core sections of high and low energy loadings extending
in lengthwise contact with said mass; a booster type detonator for
said explosive within said mass and adjacent each high energy core
section, and detonatable by detonation energy transmitted from said
high energy section adjacent thereto; each said high energy core
section having a loading of at least 25 grains PETN (or equivalent)
per foot sufficient to provide detonation energy for detonation of
said booster adjacent thereto, and detonatable by detonation energy
transmitted from an adjacent low energy core section described
below; and each said low energy core section having a sufficient
loading to provide detonation energy for transmission to an
adjacent high energy core section to cause detonation of same, but
not exceeding about 18 grains PETN (or equivalent) per foot,
whereby said system provides for detonator cord type initiation of
said slurry type explosive without substantial loss in detonation
energy of same.
2. In an explosive system of claim 1 a columnar gelled aqueous
slurry type explosive as said mass.
3. An explosive system of claim 2 wherein said slurry explosive is
free from any ingredients which are, per se, explosives.
4. An explosive system of claim 2 wherein said slurry explosive
contains dispersed gas bubbles to facilitate sensitivity.
5. An explosive system of claim 2 wherein the core loading of each
high energy core section is up to about 200 grains PETN (or
equivalent) per foot; and the core loading of each said low energy
section is within the range of from about 2 to 12 grains PETN (or
equivalent) per foot.
6. An explosive system of claim 2 wherein said detonator cord
extends from said mass to an external initiator source
therefor.
7. In an explosive system of claim 2 a plurality of said boosters
spaced apart along the length of said columnar mass, each said
booster containing a passageway extending therethrough, and a high
energy section of said detonator cord disposed within each said
passageway.
8. An explosive system of claim 2 containing only one booster, and
said booster positioned within said columnar mass at substantially
one end thereof.
9. A system of claim 7 wherein said boosters are spaced apart
substantially equidistantly.
10. A system of claim 7 wherein the length of said columnar mass is
in the order of from about 2 to 50 feet and said boosters are
successively spaced apart a distance of from 5 to 20 feet.
11. An explosive system of claim 10 wherein said explosive contains
a sensitizing proportion of dispersed gas bubbles, and guar gum in
cross-linked form to provide a resulting column of gelled aqueous
slurry explosive.
12. An explosive system of claim 1 wherein at least one booster and
high energy core section adjacent thereto constitutes, as an
integral unit, said high energy section having a core loading of at
least 200 grains PETN (or equivalent) per foot.
13. An explosive system of claim 12 where said core loading is
300-700 grains PETN (or equivalent) per foot.
14. An explosive system of claim 2 wherein said detonator cord
extends within said mass in said lengthwise contact therewith.
Description
This invention relates to detonator cord initiated aqueous slurry
type inorganic oxidizer salt explosive systems having improved
detonation energy characteristics.
Aqueous inorganic oxidizer salt explosives of the aqueous slurry
type have been used extensively in recent years. These explosive
compositions comprise an inorganic oxidizer salt or a mixture of
such salts as the basic explosive ingredient, together with water,
and, as a sensitizer, a high explosive such as TNT, tetry or PETN,
a finely divided metal such as aluminum or a magnesium alloy, or
smokeless powder. A gelation agent, or other suitable thickener, is
generally included to impart additional consistency to preclude
settling of the individual ingredients and to facilitate handling.
These slurry type compositions are generally insensitive to
detonating action of a No. 8 blasting cap and hence
cap-insensitive, but are readily initiated by action of a suitable
booster charge, generally a high explosive such as PETN, tetryl,
composition B and the like, in turn initiated by action of a
blasting cap, or a detonator cord, or fuse. Such inorganic oxidizer
salt explosive compositions of the aqueous slurry type are well
known, as exemplified in U.S. Pat. Nos. 3,235,425, 2,930,685,
2,836,484, and others.
The use of a detonator cord for initiation of the booster charge is
often preferred inasmuch as it is reliable in performance and is
readily handled during emplacement of the explosive system, and its
use eliminates the need for electrical initiation means which are
always susceptible to failure resulting from faulty circuiting, or
misfire by static charge and/or stray currents, and at best require
careful and time-consuming handling to assure satisfactory
emplacement in the explosive system.
However, in the use of a detonator cord initiator in aqueous slurry
inorganic oxidizer salt type explosives, it is generally required
that the core loading be in order of at least 25 grains, more often
50 grains or higher, of PETN (or equivalent) per linear foot, to
assure reliable detonation of the booster charge; and, when the
detonator cord extends to the embedded booster, within, or along
side of, the mass of emplaced main explosive charge, there is a
loss in detonation energy of the main charge that is not
encountered when the initiation is done by nondetonating cord
initiator means. It has been observed that under such shooting
conditions there is a lateral transmission of detonation energy
from the cord to the adjacent, or surrounding, mass of main
explosive charge with accompanying loss in detonation energy of the
main charge. Although the phenomenum is not clearly understood, it
appears that the detonation energy loss is due to compression, and
accompanying density increase, of the main slurry charge, that
takes place in response to force of the laterally transmitted
energy.
I have found that such loss in detonation energy can be markedly
reduced, or substantially eliminated, when the detonator cord
contains alternate high and low energy loadings. My invention is
based on the discovery that a requisite high loading can be
disposed adjacent each booster charge in the system, in detonating
relationship therewith, and that a markedly lower energy loading
can be utilized along the remainder of the cord length which is
sufficient for transmission of requisite detonation energy to the
higher core loading in the booster area but insufficient for
lateral transmission of any significant amount of detonation energy
to the adjacent or surrounding mass of main explosive; and that
under such conditions there is no appreciable loss of detonation
energy from the main explosive charge. It is therefore an object of
the invention to provide such an explosive system.
In accordance with the invention, a detonator cord-booster
initiated cap-insensitive aqueous slurry type inorganic oxidizer
salt explosive system, having markedly reduced detonation energy
loss, is provided, which comprises a detonator cord having
alternate core sections of high and low energy loadings extending
in lengthwise contact with a mass of said explosive; a booster type
detonator for said explosive within said mass and adjacent each
high energy core section, and detonatable by detonation energy
transmitted from said high energy section adjacent thereto; each
said high energy core section having a loading of at least 25
grains PETN (or equivalent) per foot sufficient to provide
detonation energy for detonation of said booster adjacent thereto,
and detonatable by detonation energy transmitted from an adjacent
low energy core section described below; and each said low energy
core section having a sufficient loading to provide detonation
energy for transmission to an adjacent high energy core section to
cause detonation of same, but not exceeding about 18 grains PETN
(or equivalent) per foot, whereby said system provides for
detonator cord type initiation of said slurry type explosive
without substantial loss in detonation energy of same.
Any suitable high energy core loading of at least 25 grains PETN
(or equivalent) per foot is utilized, the high energy core per-foot
loadings often being as high as 200 grains, and in preferred
practice in the range of from about 50 to 100 grains. Any suitable
low energy core loading not exceeding 18 grains PETN (or
equivalent) per foot is utilized, the low energy core per-foot
loadings often being as low as 0.2 grain, and in preferred practice
from about 2 to about 12 grains.
In preferred practice, the mass of emplaced explosive is columnar
and has a length of from 2 to 50 feet, and a plurality of booster
charges is disposed along the length of the columnar mass, often
successively spaced apart a distance of from 5 to 20 feet; the high
energy core loadings are at least about 50 grains PETN (or
equivalent) per foot, and the low energy core loadings are at least
about 2 grains per foot. However, the system often contains a
single booster charge, generally at or in close proximity to one
end of the column with the low energy section of the cord leading
from the booster to the adjacent upper end of the slurry mass for
communication with an external initiator means, generally an
electric blasting cap or a trunk line type of detonator fuse.
In another embodiment, the core loading of any one or more high
energy core sections can be sufficiently high to constitute an
integral unit of high energy core section and adjacent booster. In
that embodiment, the loading of the high energy core section is at
least 200, and preferably 300-700, grains PETN (or equivalent) per
foot and eliminates the need for maintaining the booster adjacent
thereto, as a separate unit.
The invention is illustrated with reference to the drawings, of
which,
FIG. 1 illustrates an explosive system of the invention emplaced
for shooting in a bore hole; and
FIG. 2 is a view along the line 2--2 of FIG. 1 showing a booster
charge and high energy core section of the assembly of FIG. 1 in
detonating relationship therewith.
Referring to FIG. 1, explosive system 10, in bore hole 11,
comprises a columnar mass 12 of gelled aqueous slurry type
inorganic oxidizer salt explosive 13, detonator cord 21 extending
lengthwise within mass 12 and having continuous core 22 with
alternate core sections b, d and f of high energy loading and a, c
and e of low energy loading, and spaced booster type detonators 17,
18 and 19 within the explosive mass. Explosive 13 is detonated by
detonation energy transmitted from boosters 17, 18 and 19 which in
turn are detonated by detonation energy transmitted respectively
from high energy core sections b, d and f; and high energy core
sections b, d and f are respectively detonated by detonation energy
transmitted from adjacent low energy core sections a, c and e.
Detonator cord 21 comprises a continuous core 22 of high explosive,
such as PETN, covered with a suitable plastic type sheet 23 and
extends, within mass 12, from the stemming level 14 substantially
to the bottom 15 of the bore hole.
Boosters 17, 18 and 19 respectively contain passageways 17', 18'
and 19' extending therethrough co-directionally with detonator cord
21; and cord 21 extends through each of passageways 17', 18' and
19'. Boosters 17, 18 and 19 are spaced so as to contain high energy
loading sections b, d and f respectively within passageways 17',
18' and 19' and hence to position each booster type detonator
adjacent each high energy section of core 22.
Each high energy section b, d and f is supported in position within
the respective booster unit in any suitable manner such as by tapes
17a and 18a wrapped around cord 21 adjacent both the top and bottom
ends of booster assemblies 17 and 18 respectively, tape 19a wrapped
around cord 21 adjacent the top end of booster 19 and section g or
cord 21 as a knot g' adjacent the bottom end of booster 19. Each
tape is wrapped to a diameter greater than that of the respective
passageways 17', 18' and 19' and knot g' is of cross-sectional
dimension greater than the diameter of the passageway 19'.
Each high energy core section b, d and f has a loading of at least
24 grains PETN (or equivalent) per foot sufficiently high to
respectively provide the requisite detonation energy for
transmission to the boosters 17, 18 and 19. Each low energy core
section a, c and e has a suitable loading below 18 grains PETN (or
equivalent) per foot, which is sufficient to provide detonation
energy for transmission to the adjacent high energy core section to
cause detonation of same. Although end core section g does not
function to initiate a high energy core section, it does not exceed
the maximum for the core sections a, c and e in order to provide
insufficient detonation energy for lateral transmission to the
surrounding main explosive mass to cause any substantial detonation
energy loss of the mass. Advantageously, the loading of small core
section g is generally the same as that of sections a, c and e. If
desired, means other than low energy section g can be utilized for
support of detonator cord 21 in booster 19.
Section a' of detonator cord 21, outside mass 12, and having a core
loading genrally about the same as that of the low energy core
loadings within mass 12, extends upwardly from section a through
stemming material 16 to connect with a trunk line 25 above ground
as the initiating energy source, and is secured to line 25 by knot
means 25a.
In the operation of the embodiment of FIG. 1, the "down line" or
detonator cord 21 is initiated by detonation energy transmitted
from trunk line 25 via extended end section a'. There is, of
course, detonation along the entire length of cord 21, there being
in succession, detonation of sections a, b, c, d, e, and f with no
substantial lateral transmission of detonation energy to the
surrounding slurry mass from the low energy loaded core sections,
but with detonation of each booster charge and accompanying release
of detonation energy lost heretofore due to lateral transmission of
energy from the cord to the main charge 13.
The aqueous slurry inorganic oxidizer salt explosives of the system
of the invention are generally those which are free from
ingredients which are, per se, explosives, and contain dispersed
gas particles to facilitate sensitivity. Gelled aqueous slurry
explosives in which the thickener is guar gum in crosslinked form
are often utilized.
A composite cord of unitary construction having a connecting
portion of generally low brisance and a detonating portion of
higher brisance for transferring low energy signals and capable of
performing useful comparatively high energy work at one or more
work stations is, per se, disclosed in U.S. Pat. No. 3,241,489.
The invention is further illustrated with reference to the
following examples.
EXAMPLE 1
In each of three tests, a bagged columnar cap-insensitive aqueous
slurry explosive 5 inches in diameter by 26 inches in length was
packed, and detonated at 40.degree. F., in an iron pipe open at one
end, in response to action of a 500 gram Pentolite booster charge
(including a 3 gram PETN insert) embedded in one end of the
columnar mass. In the first test, the booster was initiated by
action of a No. 8 electric blasting cap supported in a well
extending into the booster body in detonating relationship
therewith, and connecting with an outside firing current source via
the lead wires extending along side the columnar mass intermediate
the side wall of the bag and the inner wall of the pipe; in the
second test, the booster was initiated by action of a detonator
cord having a uniform loading of 50 grains PETN (or equivalent) per
foot and extending from initiating contact with a No. 8 electric
blasting cap outside the mass, along side the columnar charge from
the end thereof opposite the booster intermediate the side wall of
the bag and the inner wall of the pipe, and then into a well
extending into the booster body in detonating relationship
therewith; in the third test, the booster was initiated by action
of a detonator cord extending into detonating relationship
therewith in the same manner as described with reference to the
second test except that in this test the core loading of the cord
within the booster well was 54 grains PETN (or equivalent) per foot
and the core loading of the cord along its remaining length was 4
grains PETN (or equivalent) per foot. Density of the slurry
explosive in all instances was 1.08 grams per cc. and results of
the tests are summarized as follows: ##SPC1##
The above data demonstrate that when the main aqueous slurry type
explosive charge was initiated by a detonator cord under
conventional core loading conditions, the detonation energy was
only 62 percent of that obtained under nondetonator-fuse initiating
conditions and hence the loss was 38 percent; whereas, in a system
of the invention, the detonation energy was 90 percent of that
obtained under nondetonator-fuse initiating conditions and hence
the loss was 10 percent, thus providing a substantial reduction in
the loss of detonation energy of the main charge in detonator cord
initiated aqueous slurry explosive systems heretofore.
EXAMPLE 2
In each of two tests, a 5 inch diameter .times. 26 inch length
bagged columnar mass of aqueous slurry explosive was detonated in
an iron pipe under hydrostatic pressure of 32 p.s.i.g. at
40.degree. F. by a 2-pound Pentolite booster (including a 3- gram
PETN insert) embedded in one end of the mass. In the first test,
the booster was initiated by action of a No. 8 electric blasting
cap supported within the booster and connecting with an external
firing current energy source. In the second test, the booster was
similarly positioned and was initiated by action of a detonator
cord, having a uniform core loading of 50 grains PETN (or
equivalent) per foot, and extending from initiating contact with a
No. 8 electric blasting cap outside the mass, first into the end of
the mass containing the booster and then through a passageway
extending through the booster, and on through substantially the
remainder of the length of the mass. The slurry explosive mass was
the same for both tests, as follows:
Ingredients Parts by Weight
__________________________________________________________________________
Water 15.8 Ammonium nitrate 50.0 Sodium nitrate 15.0 Ethylene
glycol 4.4 Silicon alloy (85 percent Si) 12.5 Guar gum* 1.4 Sodium
nitrite 0.08 Specific gravity 1.06-1.07
__________________________________________________________________________
The results of the tests are further summarized as follows:
Test 1 Test 2
__________________________________________________________________________
Detonator for the boosters EB Cap Detonator cord No. 8 (50 grains
PETN per foot) Detonation rate, m/sec. 4250 3100 (slurry explosive)
Total energy, main explosive charge* 0.960 0.535
__________________________________________________________________________
The data of Example 2 further demonstrate the loss in detonation
energy of the main explosive charge that takes place when the
detonator cord of a conventional detonator cord-initiator system,
for aqueous slurry type explosive, extends in contact with the main
explosive mass -- within, and substantially along the entire length
of the mass, in the present instance.
Any suitable detonator cord-sensitive booster type high explosive
charge can be utilized as a booster in the explosive system of the
invention, exemplary of which are composition B, Pentolite, TNT,
Amatol, and PETN. Often such charges also contain a small portion
of a supplemental explosive of sensitivity greater than that of the
main booster charge, as an "insert", in detonating relationship
with the detonator cord initiator and in turn with the booster
charge to facilitate detonation of the booster charge in response
to initiating action of the detonator.
* * * * *