US2463709A - Ammonium nitrate explosive - Google Patents

Description

arch 8, 194% D. M. MOFARLAND AMMON IUM NI TRATE EXPLO S IVE Filed Nov. 16, W45

INVENTOR Patented Mar. 8, 1949 AMMONIUM NITRATE EXPLOSIVE David M. McFarland, West Chester, Pa., assignor to Atlas Powder Company, Wilmington, Del., a corporation of Delaware Application November 16, 1943, Serial No. 510,551

6 Claims.

The present invention relates toammonium plosive assembly which is relatively safe yet Gelatin dynamite has been found to be a most eflicient core material. However, other waterproof high explosives may be used for cores. For example, a straight nitro glycerine dynamite contained in a water-proof bag or other water-proof container, or electro-plated TNT may be used.

The invention is more specifically described in connection with the accompanying drawing which illustrates a specific embodiment of the invention detonates with complete efficiency. and in which Figure 1 is a longitudinal section A further object of the invention is t provide of an explosive assembly of the present invention, a method of exploding wet ammonium nitrate exand Figure 2 is a cross-sectional view of the same plosives. assembly taken on line 2-2 of Figure 1.

For some time, ammonium nitrate explosives The explosive assem y c mp a P p have been employed where a low-cost explosive tridge H i erimped e ehds- Inside a having a relatively high strength but low brisance t dee ll l es e p os e a e an am m is desired. It has, however, been found imperative nitrate composition sensitized with nitro glycerto water-proof carefully ammonium nitrat exinc. Running through charge I3 is central core plosives before use. Such water-proofing has Which is a e up Of pape W pp d cartridg been accomplished in a number of ways. One of gelatinized nitro glycerine dynamite l'l. Core common method has been to up ly th explosive i5 is shown extending throughout the assembly. in sealed metal cans. Another similar method Alternatively. the core y e d o y partially has been to pack the explosive in water-proof. through the assembly. Ceres extending through bagging materials. A third method, which h only about one-half of the assembly are satisfacbeen found somewhat elrective to Water-proof 2 ryt s p fe w v r best pr p ammonium nitrate explosives, has been to supply tien to p o de a o running ou hout the asthem in a composition which gels on contact with sembly. water. The gel produced then protects the am- The core i usua y O i her velocity than the monium nitrate from further contact with water. ammonium nitrate explosive, and consequently All of these methods are expensive and require fiuences the longitudinal velocity of the assembly unusually careful methods of preparation to see as a whole. The longitudinal velocity of the asthat water-proof characteristics are maintained. sembly y be l ed y varyi t a e r If any of these methods fail and an ammonium of the core or by varying the tyfie 0f the o nitrate explosive as heretofore prepared does besince gelatin dynamites and other water-proof come wet, its susceptibility to initiation and its explosives are available in a number of different ability to propagate detonation are severely low- Velocitiesered, and its efiiciency often becomes so poor as Cores small enough in diameter to upy as to render it entirely useless. Blasting shots made little a o the t n l ea o t e enwith such wet ammo i m nitr t give off dense tire assembly have been found to be satisfactory. red or yellow fumes indicating incomplete detona- On the other h n cores ay be used which oction' and also give unsatisfactory results b a cupy as much as 15% of the cross-sectional area of the power lost When the explosive is wet. 0f the as e y- It has been found that, according to the pres- In general cores having velocities, measured in ent invention, an ammonium nitrate explosive t p n wi h 1%" ca trid es, much lower than assembly is provided which produces complete 6,000 e p s d o much i r an 00 and emcient blasts even though wet. The disfeet p Second 0 not produce the o es .covery has been made that if ammonium nitrate a sis sensitized, and if a water-proof high explosive C s a usua y t v n ently mad of is used to initiate the ammonium nitrate, it may p f ed an apped Cartridges o e plosive. be detonated efliciently even when it is so Wet as However, they may b uded in the a s y to be fluid. without any wrapping.

According to the present invention, a water- Usually assemblies of the yp f t P e absorbent sensitized ammonium nitrate explosive invention are employed in diameters greater than is packed in a water-pervious cartridge and pro- 2". vided with a core of water-proof high explosive. The ammonium nitrate explosive which mak s up the main body of the assembly of the present invention may be of the type of any of the waterabsorbent ammonia dynamites now extensively used. It has, however, been found necessary to employ a small quantity of sensitizer with the ammonium nitrate explosive. The sensitizer for the ammonium nitrate may be selected from the wellknown sensitizers for ammonium nitrate. As examples may be listed mineral oils, vegetable oils, and other oily materials as declared in application of Claude H. Carey, Ser. No. 351,211, filed August 3. 1940, now abandoned, nitro compounds, such as dinitrotoluene, trinitrotoluene, cyclonite, nitric esters, such as nitro-glycerin, nitro-glycol, and

' nitro-sugars, and metal powders, such as aluminum dust. The amount of sensitizer may be considerably less than that present in many commercial dynamites. For example, quantities of nitro glycerine amounting to as low as 4% of the ammonium nitrate explosive composition are found to be satisfactory. On the other hand, the invention may be employed with dynamites containing as high as 20% nitro glycerine.

' When the assemblies of the present invention are used wet, it is almost always necessary to initiate them in the core. This may be done, for example, by inserting a blasting cap detonator or detonating fuse into the core, or it may be done by charging a quantity of gelatin dynamite or other water-proof explosive, containing a detonator, into the charge hole along with the exploslve assembly and adjacent to its core. Usually the latter method will be found simpler.

The explosive assembly of the present type should, of course, not be left in unconfined places under water for long periods of time lest the highly soluble ammonium nitrate leach away completely. Assemblies of the present type are highly satisfactory, however, when left for long periods of time under water in more confined places. Under such conditions, even if the ammonium nitrate does leach, it does not get away from the place where it is desired to use it. For example, explosive assemblies of the present, invention are very useful in quarry blasting. In uses of this nature, the explosive is often loaded in well drill holes, containing many feet of water;

' and since extensive loading operations are usually necessary for any one blast, the explosive must often remain under water for a period of several days. The present assemblies are also very useful in strippin operations where frequently holes more nearly horizontal are used. A large amount of water usually seeps into such holes.

When water is absorbed in the assemblies of the present invention, it is found to produce positively beneficial results. The water content appears to lower the brisance of the ammonium nitrate without materially lowering its strength. Consequently, more of a heaving and less of a shattering action is obtained. This is highly desirable in quarry and stripping blasting.

When loading conditions are dry and explosive assemblies of the present invention ar used, it often is desirable to wet the cartridges well before firing. This may often be most effectively done by pouring water down the bore hole after the explosive assemblies have been charged.

To produce the lowered brisance characteristics of the explosive assemblies of the present invention, it usually is desirable that water be absorbed in excess of about 6% of the weight of the explosive composition. I

It is also within the contemplation of this 4 invention to supply the water in the explosive composition at the time of manufacture as well as to supply it in the loading operation.

It should be noted that when the assemblies of the present invention are wet from the outside, as in loading wet bore holes or introducing water into a loaded hole, the outer ortions of the assembly absorb more water than the inner portions of the assembly. This is believed to be definitely advantageous, since shattering explosive action appears to increase as detonation proceeds from the center of the cartridges outwardly. It is postulated that the wetting of the outside portions of the cartridge tempers this action, producing the better heaving characteristics.

Examples of assemblies prepared according to the present invention are set forth below.

Example I Explosive assemblies were prepared in the form shown in the drawing using paper cartridges having glued seams. The composition of the waterabsorbent ammonium nitrate explosive was as follows:

This composition was packed in paper shells six inches in diameter around a core made of 1 A" thirty per cent nitro glycerine gelatin cartridges. The entire assembly was about 24" long and weighed about 25 lbs.

A limestone formation was blasted using these cartridges in well drill holes containing as much as 16' of water. Each hole was primed at the top with gelatin dynamite into which was inserted a #6 electric blasting cap. The primer was lodged between the last two assemblies loaded into the bore hole. A number of the assemblies were punctured before loading. The blast was entirely satisfactory and produced no red or yellow fumes indicative of poor detonation.

Example II Several blasts were conducted in another limestone quarry using cartridges having non-waterproof shells. The assemblies comprised sixty per centnitro glycerine gelatin cores 1%" in diameter inside water-absorbent ammonium nitrate explosive having the following composition:

Per cent Ammonium nitrate 44.8 Nitro glycer 8.0 Sodium nitra 33.0 Chalk 0.5 Carbonaceous ingredients 13.7

These cartridges were each 5 /2" in diameter, about 27" long, and weighed about 25 lbs. They were loaded in well drill holes containing between 15' and 20' of water, and were initiated by electric blasting caps each inserted into a 2" x 4" cartridge of 40% gelatin loaded between the last two assemblies in each hole.

Again the blasts were entirely satisfactory and produced no objectionable red or yellow fumes. The powder employed in these assemblies was of an average of 42% weight strength per bore hole.

Other blasts in the same location, and under the same conditions. were made in holes loaded with ammonium nitrate explosives in water-proof containers. Using an approximately equal powder factor, in these last blasts, powder having an average weight strength of about 67% per bore hole failed to show as good results as did the blasts in which assemblies of the present invention were used.

It may be seen that according to the present invention an assembly is produced which maybe manufactured of low-cost materials and without excessive precautions to provide for Water-proofing, but yet an assembly more eificient than assemblies heretofore known is obtained.

In this specification and claims, the term water-pervious shell" is meant to include shells which will admit water under conditions of 13 pounds per square inch water pressure held for 24 hours.

What is claimed is:

1. An explosive assembly which comprises a water-pervious shell, a water-absorptive ammonium nitrate explosive composition including a sensitizer in said shell, and a water-proof high explosive core said assembly having a diameter greater than about 2 inches and said core providing from about 3% to about 15% of the cross sectional area ,of said assembly.

2. An explosive assembly which comprises a water-perviousshell, a water-absorptive ammonium nitrate explosive composition including a nitric ester sensitizer in said shell, and a waterproof high explosive core said assembly having a diameter greater than about 2 inches and said core providing from about 3% to about 15%-of the cross sectional area of said assembly.

3. An explosive assembly which comprises a s5 water-pervious shell, a water-absorptive am monium nitrate explosive composition including a nitro glycerine sensitizer in said shell, and'a water-proof high explosive core said assembly.

having a diameter greater than about 2 inches and said core providing from about 3% to about 15% of the cross sectional area of said assembly.

.aeea'roo I 4. An explosive assembly which comprises a water-pervious shell, a water-absorptive ammonium nitrate explosive composition including a nitric acid sensitizer in said shell, and a gelat- 5 inized nitro glycerine core said assembly having a diameter greater than about 2 inches and said core providing from about 3% to about 15%'of the cross sectional area of said assembly.

5. An explosive assembly which comprises a 10 water-pervious shell, a water-absorptive am-' monium nitrate explosive composition including a nitro glycerine sensitizer in said shell, and a ,gelatinized nitro-glycerine core said assembly having a diameter greater than about 2 inches 5 and said core providing from about 3% to about of the cross sectional area of said assembly.

6. An explosive assembly which comprises a water-pervious shell, a water-absorbtive ammonium nitrate explosive composition including a nitric ester sensitizer and containing more than about 6% water in said shell, and a gelatinized nitro glycerine core, said assembly having a diameter greater than about 2 inches and said core providing from about 3% to about 15% of the cross-sectional area of said assembly.

A ID M. McFARLAND.

REFERENCES .3 The following references are of recordin the file" of; this. Patent: UNITED" swim PATENTS Number Date Name 7 r, 1,502,646 Hediiij; July 22. 192a 2,048,831 .White- V July 28,1936 roamenramh'rs to Number 3 fC6untry-' 1* "21 Date 449,909; 5 Great Bntain; July 6.193s

Certificate of Correction Patent No. 2,463,709. March 8, 1949. DAVID M. MoFARLAND It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 4, claim 4, for the word acid read ester;

and that the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the casein the Patent Oflice. Signed and sealed this 2nd day of August, A. D. 1949.

THOMAS F. MURPHY,

Assistant (lomma'ssioner of Patents.

Certificate of Correction Patent No. 2,463,709. March 8, 1949. DAVID M. McFARLAND It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 4, claim 4, for the wor acid read ester;

THOMAS F. MURPHY,

Am'atant flommim'aner of Patents.

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