US 2760434 A
Description (OCR text may contain errors)
Aug. 28, 1956 J. A. RUTH 2,760,434
EXPLOSIVE Filed Jan. 10, 1952 INVENTOR. JOHN A. Ru TH Maw AGE/VT EXPLOSIVE John A. Ruth, Clinton, Ind., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Application January 10, 1952, Serial No. 265,830 2 Claims. (01. 102-20) This invention relates generally to explosives and more particularly to novel explosive shaped charges having improved properties.
It has been known in the blasting art that the energy developed by an explosive charge can be concentrated and a greater depth of penetration achieved by modifying the shape of the surface of the charge which faces the media to be blasted. For instance, the surface is provided with a cavity therein which may be conical, pyramidal, parabolic or the like; charges having such cavities being referred to hereinafter as shaped charges. This phenomenon is advantageous in numerous blasting operations such as, for example, in perforating the casing and media surrounding oil well bore holes, in some mining operations, tapping metallurgical furnaces and in armor piercing projectiles. In some of these operations the media must be penetrated to a relatively great depth without destruction tates atent of a large area of the surface thereof and, in most instances, the blasting must be accomplished with a relatively small explosive charge. It has also been known that even greater penetration is attained with shaped explosive charges provided with a non-explosive covering or liner conforming to the shaped surface thereof. This improvement has been attributed to the projection of particles of the liner at a high velocity when the explosive is fired. The shaped charges utilized in blasting operations of this type have been formed theretofore from secondary explosive compositions having a relatively high degree of bri-sance such as trinitrotoluene, pentaerythritol tetranitrate, cyclotrimethylenetrinitramine or mixtures thereof. While the foregoing explosives have been used extensively because of their relatively high brisance, it has long been recognized that greater penetration than is obtainable with shaped charges of these explosives would be advantageous in any of the foregoing types of blasting operations and particularly so in the perforation of oil well bore holes and in armor piercing projectiles where maximum depth of penetration per unit amount of explosive charge is important.
It is an object of this invention therefore to provide an improved explosive charge having improved penetrating properties. Still another object of this invention is to provide an improved method for perforating the walls of oil well bore holes. A further object of this invention is to provide novel explosive shaped charges. It is a still further object of this invention to provide explosive charges of high brisance and a method for using them.
In accordance with this invention, the foregoing objects as well as others which will become apparent from the following description are accomplished by providing methylenedinitramine as an explosive. Methylenedinitramine in granular or crystalline form can be formed readily into shaped charges by the methods used heretofore with granular trinin-otoluene and the like and the resulting charge has great penetrating power and other advantages, which will become apparent from the detail description hereinafter. This invention further contemplates an improved process for perforating various media such as, for
instance, the wall of oil well bore holes, armor and similar materials with shaped charges of methylenedinitramine.
Methylenedinitramine can be prepared by a series of reactions in which methylenebis-N-acetamide, methylenebis-N-acetarnide mononitrate, methylenebis-N-(N-nitro) acetamide, the barium salt of methylenedinitramine and finally methylenedinitramine are formed in that order, in accordance with the process described by Brain and Lamberton published in the Journal of the Chemical Society, June 1949, pp. 1633-5.
The surface of the methylene dinitramine charge facing the medium to be perforated is modified to concentrate the energy developed by the explosion thereof in the known manner, the particular configuration most advantageous varying with the type of operation in which the charge will be utilized. An explosive charge having a cavity in the shape of an inverted cone in a surface thereof is particularly advantageous in tapping metallurgical furnaces. Armour piercing projectiles containing shaped charges of methylened-initramine in which the cavity is parabolic are particularly effective. In each instance it is preferred that the cavity in the charge be provided with a nonexplosive covering or liner. The liner may be made from metal, ceramic, plastic or similar non-explosive material and should conform substantially to the shaped surface of the explosive charge.
In order to more fully describe and to clarify this in vention, the following is a description of one embodiment thereof:
Referring to the accompanying drawing, a longitudinal sectional view of an oil well casing 16 is shown with a perforating device 13 positioned therein and substantially adjacent to the wall 12 of the casing 16. The perforating device 13 is composed of two external glass parts 1 and 3. The base portion ll contains a relativelysmall pressed explosive charge 5 of methylenedinitramine crystals separated from the larger pressed charge 10 of wax coated met-hylenedinitramine crystals by means of a paper disk 6. The coating of wax is applied to the methylenedinitrarnine crystals to be used for charge 10 by a process which comprises mixing a solution containing about two parts of a microcrystalline petroleum wax known to the trade as Superla N o. 3 Special and which has a melting point of about 76 C. dissolved in about 80 parts by weight carbon tetrachloride with about 50 parts methylenedinitramine and evaporating the carbon tetrachloride therefrom by means of an air steam. A conical shaped cavity is formed in the surface of charge 10 and covered with a brass liner 7. The flange 4 of the open end of the base portion 1 of the device 13 is coated with a layer of pitch 1'7 and inserted into the flange 18 of nose portion 3 forming a friction fit and water-proof juncture therewith. The ogive 19 of nose portion 3 of the perforating device 13 extends through an opening in aluminum foil 8 and is supported thereby. A primac-ord 9 extends through opening H in aluminum foil 8 and around the base portion 3 between protuberances 2 and 15 and is drawn tightly through-opening 14 in aluminum foil 8, thus supporting and exerting pressure against the base portion 1 of the device 13 and wedging the entire assembly in position with respect to the aluminum foil 8. When it is desired to fire the methylenedinitramine charges 5 and 10 the primacord 9 is initiated by means of a co ventional electric detonator or any other suitable means which initiates untreated charge 5 of methylenedinitramine which fires the main charge 10. A jet of metal from liner 7 as well as the energy developed by the explosive charges 5 and M are projected against the wall 12 of casing 16 perforating it and penetrating into the media thereabout.
It has been found that methylenedinitramine shaped in the Ballistic 'Mor-tar tion of methylcnedinitramine at a.
: charges have greater penetrating properties than any of the explosives disclosedfor this purposepMethylenedinitrarnine has been. found to have a strength of about 1.5 as compared to 1.6- for trinitrotoiuene as determined. and a brisance of about two i times that of trinitrotoluene in the Lead Block or 'irauzl Block'Test. The packing density of methylenedinitra- 9 property thereof as a highdetonation rate is advantageous in blasting operationsutilizing shaped charges. i
As indicated hereinbefore, shaped charges of meth ylenedinitramine are superior to the explosives heretofore proposed for tapping metallurgical furnaces. In tapping I furnaces with explosiveshaped charges, a hole is usually drilled entirely throught'he fire clay plug in the tap hole. I
This leaves only .arelatively thinbarrier of solid metal adjacent'the inner end of the plug to'preventjfiow of the i The shaped charge is. I rammedinto the holethus formed in the plug and initi ated in perforate the solid metal incrustation.
molten metal from the furnace.
The ex- 9 of large surfacearea of the medium to be perforated or plosive charge is usually insulated .by covering it with insulating material orbyramming insulating material into theholeprior to insertion of the explosive. 1
g I I When inethylenedinitramine shaped charges are utilized is notnecessary to drill entirely through the fire clay as these charg'es will penetrate, an appreciable thickness of the clay as well as the soiid metal. Usually,depen'ding upon the size of charge used, the hole about two-thirds of the thickness of the plug thus leaving an added barrier against how of, the molten metai and reducing the hazard involved in these processes; The
' me'thylenedinitramine can be initiated by the heat from the furnace or a detonator can be embcddedin the charge and ignited electrically to initiate the explosion thereof, if desired. The methylenedinitramine shaped charge can be formed by pressing into a suitable container provided with a concave surface and insulated in accordance with conventional methods.
Methylenedinitrarnine because of its increased penetrating properties can also be used advantageously in armor piercing projectiles provided with a concave surface at the striking end thereof and also for forming drill holes or channels in mine walls for blasting cartridges.
Numerous variations from the details of the foregoing embodiments such as, for example, forming the perforating device from plastic or metal, or substituting other types of containers for the perforating device can be made Without departing from the spirit of this invention.
In the embodiment for perforating the media surround ing oil Well bore holes, other means for supporting the perforating device can be provided, the one described being only a preferred and convenient method. In this particular method, however, the primacord serves a twofold purpose of supporting the device 13 as Well as serving to initiate the methylenedinitramine charges. Likewise, initiating charges other than methylenedinitramine need extendthrough only utilized as the shaped charge I and can be handled and paraffin waxes such as lead azide might be utilized for the igniter explosive charge 5. Waxed methylenedinitramine is preferably impact sensitivity than uncoated methylenedinitraminc andshipped with less danger of inadvertent explosion. 'Uncoated methylenedinitramine can be utilized satisfactorily provided caution isobserve'd in handling.
While in the foregoing embodiments microcrystalline petroleum war was utilized, other Waxes such as ceresin, having a suitable melting. point of about 70 C. or higher can be substituted therefor.
Waxed methylenedinitramine can be utilized entirely and the more impact sensitive chargereplacedtherebyif sufficient means are provided forinitiatingthe desensitized explosive.
effective whether or not minor amountsof other explosives such as cyclotrirnethylenetrinitramine or pentaerythritol i tetranitrate are included. g
It should be apparentfron'i thcforegoing description that this invention accomplishes its objects and provides an improved explosive charg'e and an improved process.
wherein greater dcpthof penetration without destruction for penetration of heavy armor is attained.
Having thus described the invention what is claimed V and desired to secure by, Letters Patent is:
,1. A shaped charge of inethylenjedinitramine having a was: coating and compressed to packing density of at least 1.7, and combined therewith a second charge ofv uncoated 'methylenedinitramine, said shaped charge having a strength ofat least 1.5 times as great as that of trinitrotoluene and a detonation rategreater than that of trinitrotoluene. g
2. A Well bore hole perforating device comprising a container having a base portion and surface of the methylenedinitr'amine charge facing the nose portion having a cavity therein and a non-explosive liner covering and in engagement with the surface of said cavity.
References Cited in the file of this patent UNITED STATES PATENTS 989,375 Luciani Apr. 11, 1911 2,399,211 Davis et al Apr. 30, 1946 2,413,680 Blacltington et a1 Jan. 7, 1947 2,415,814 Davis et al Feb. 18, 1947 2,494,256 Muskat et al. Ian. 10, 1950 2,563,131 Old Aug. 7, 1951 2,629,325 Sweetman Feb. 24, 1953 2,649,046 Davis Aug. 18, 1953 FOREIGN PATENTS 574,271 Great Britain Dec. 31, 1945 OTHER REFERENCES Chemical Society Journal, 1949, part II, pages 1633 to 1635.
it) because it has a lower Shaped charges of methyle'ne'dinitramine are.
a nose portion fric tionally fittogether, an impact sensitive explosive charge 1 and a charge ofwax coated methylenedinitramine com pressed to a density of at least 1.7 in said container, the