Waterproof package for explosives

OR »200 «743

ShARGH ROOM

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Aug. 17, 1965 G. L. GRIFFITH etal 3,200,743

WATERPROOF PACKAGE FOR EXPLOSIVES Filed Oct. 24, 1963

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Inventors:

George L. Griffith

Thomas P Dowling fi their Attorney

United States Patent Office

3,200,743

Patented Aug. 17, 1965

3,200,743

WATERPROOF PACKAGE FOR EXPLOSIVES George L. Griffith, Coopersburg, and Thomas P. Dowling,

Fullerton, Pa., assignors to Trojan Powder Company, Allentown, Pa., a corporation

Filed Oct. 24,1963, Ser. No. 318,629

Claims. (CI. 102—24)

This invention relates to low sensitive explosives, nitrocarbonates, and other explosives which have no inherent water resistance and therefore lose usefulness if not packaged so as to be completely water resistant and which must have a density when ready for use sufficient to allow the cartridge to sink in water but which density should be lower than that at which the explosive would tend to lose sensitivity.

The principal object of this invention is to provide a container of such materials as to furnish the stiffness and strength of conventional spiral wound shells together with the ease by which it can be closed by simple crimping and wax sealing and yet be completely water resistant although permitting normal methods of filling and use.

An important object of the invention is to provide a j package of an ammonium nitrate explosive which can readily be filled by auger loading.

/ A third object of the invention is to provide an inexpensive package of low sensitive explosive which can be filled by auger loading, will be effective under extreme heads of water pressure and have a density greater than 1 and not over 1.15.

Many endeavors have been made to meet the requirements of an inexpensive package for explosives of the general type of prilled ammonium nitrate with a carbonaceous material and they have usually been successful in most of the requirements, which are many, but each leave a desirable feature only partially met, for example, many are too expensive, others withhold water but not for high heads or long immersions, others will not sink in water, while others have too great a density, some are perfectly waterproof but this feature is often lost in use or in loading, and others cannot support the expected loading pressures.

The requirements and difficulties are given in greater detail in the following:

The use of either expandable tubing or non-expandable tubing such as a burlap outer tube with a polyethylene interior liner, or a conventional spiral wound explosives shell, has a number of disadvantages—particularly when it comes to the less expensive ammonium nitrate explosives. These disadvantages would also be present in similar packages for explosives having little, if any, inherent water resistance. We will discuss first the problems associated with the packaging of nitrocarbonitrates.

Generally, all NCN’s which do not contain non-explosive sensitizers such as dinitrotoluene are completely desensitized by the addiition of even very minor amounts of water. It is possible to add water gelling agents such as Guar Gum and obtain some water resistance, but this is not only expensive, but also would not be effective under extreme heads of water pressure.

Normally, also, any NCN which consists essentially of ammonium nitrate and a carbonaceous fuel becomes extremely insensitive if packaged to a density above 1.15. It can readily be seen that to go to too high a density results in poor sensitivity; to have a package which is not completely water resistant likewise produces poor sensitivity. The industry consequently would like a total package which is water resistant and not too dense.

Another problem is obtaining a total package which is relatively stiff and firm so that it can be loaded into ragged or crooked holes. The basic disadvantage of a plastic package is the fact that it can very easily be cut or ruptured and essentially has little, if any, water resistance after being handled in a normal manner.

An additional problem is obtaining sufficient density to g allow the package to sink in water. This is extremely difficult to do since about the only way one can obtain density is by bouncing or vibrating, because the package has no inherent strength and one cannot press or screw load it.

To get around the obvious disadvantages of the all10 plastic package, certain companies have put on the market a two-ply bag: the inner ply is a polyethylene tube, and surrounding this, there is a tube of burlap, which in some instances is asphalt impregnated to give stiffness. This package is difficult or impossible to load with any presjg sure or screw equipment since the screw (in the case of the polyethylene bag) can cut through the plastic bag and destroy its apparent water resistance. Also, since it has no stiffness, it cannot support any loading pressures other than conventional bumping or vibrating.

2q For a number of years the various explosives companies have put out an NCN package which is essentially a spirally wound tube with water resistant or water impervious plies and with conventional closures which are poured with hot wax to protect the contents. Tubes or 25 shells such as this can, of course, stand appreciable pressures and they can be satisfactorily loaded by pressing or by extrusion or vibration or bumping. However, even the best paper shell with the best possible end closure is still not completely waterproof. Normally, it will stand some 3Q hydrostatic heads but field experience has definitely shown it will not stand appreciable heads of water for any long period of time.

To get around the disadvantages of the conventional explosive spiral wound shell, other companies have come 35 out with a considerably heavier spiral wound wall, which is dipped in hot asphalt or has a number of moisture vapor barrier plies which can be made essentially waterproof for a great period of time. To adequately prevent water from entering either end, metal ends have been 40 seamed to the shell, and the industry has essentially come up with a total package which is generally extremely water resistant.

This type of package can, of course, be loaded in any manner whatsoever since it has adequate strength in all respects. However, the metal ends are a disadvantage ⁴⁰ since they have a tendency to cut the cap leg wires and also the Primacord, and furthermore they introduce metal into a bore hole, which is not desirable; difficulties could be experienced with impact and friction. This is particularly true since most holes loaded with NCN’s have some ^5U appreciable amounts of high explosives either for priming or for pulling the bottom.

The most desirable package would be one which has all of the inherent stiffness characteristics of a conventional spiral wound shell, including its strength, its ease in ⁵⁵ closing by simple crimping and wax sealing, and also obviously it is the most economical type of container. However, as mentioned previously such a container is not water resistant. It would seem rather simple to embody a polyolefin plastic tube inside of a spiral wound ^&amp;0 shell and to seal the polyethylene tubing by heat sealing or by wire tying, and come up with a completely waterproof package. A number of attempts have been made to do this, but they have all presented a number of difficulties. First of all, when a spiral wound shell with a ⁶⁵ polyethylene inner tube is loaded by screwing, it is quite obvious the screw or auger can pierce or puncture the polyethylene tubing and destroy its water resistant characteristics. Also, if the material is extruded into the polyethylene tube, the extrusion pressure tends to force ‘° the polyethylene tubing down toward the bottom of the spiral wound shell. Essentially, one ends up with an

3,200,743 ³ accordion pleated tube and in most instances it is not possible to avoid this. It might be possible to have some method of holding the tube at the top of the spiral wound shell, but again, when the extrusion pressure is subjected to the sides of the plastic tube there is a tensile force exerted on the tubing which can cause it to tear or rupture. Normally, pressure extruding is more expensive and more time consuming than screw loading. Screw loading or auger loading is the preferred method.

As thus shown, there are a number of problems associated with any of the present packages which are now being marketed—particularly for NCN’s. A simple, economical and practical package which will give all of the desired characteristics and also all of the stiffness characteristics required is shown in the drawings in which the figure is a central section through a tubular package embodying the invention.

In the drawing the outer shell 10 is a conventional cylindrical body of paper spirally wound into a firm shell having a radial thickness of from a twentieth to a tenth of an inch, preferably .060 to .090. Within the outer shell there is a polyethylene bag 12 of from three to twelve, preferably six, mil thickness loosely positioned between the shell and an inner tube 14, slightly shorter than the bag and like the shell also of spirally wound paper but only about .02 thickness, the clearance between the shell and the tube being about the same or slightly greater than the thickness of the inner tube. The ; bag may have a closed bottom but usually the bottom 16 Ϊ will be closed by a suitable tie 17 or it may be heat sealed. At the top the polyethylene bag may be suitably tied or otherwise closed and the open end of the outer shell is closed by simple crimping and wax sealing as at 20.

The package thus produced is completely water resistant and can be loaded by any conventional powder loading mechanism and it will withstand any normal quarry handling and loading conditions.