US3374736A - Water desensitized water work boosters - Google Patents

Description

March 26, 1968 R. DOW ETAL 3,374,736

WATER DESENSITIZEID WATER WORK BOOSTERS Filed Aug. 2, 1966 2 Sheets-Sheet 1 Fig.1

INVENTORS RICHARD DOW PAUL E. KELLY PAUL A.

RAMW I i av WNW Y March 26, 1 968 R. DOW ETAL 3,374,736 WATER DESENSITIZED WATER WORK BOOSTERS Filed Aug. 2, 1966 2 Sheets-Sheet 2 Fig. 2 ll! 3 L I I l I'-' Fl' 9. 3A

INVENTORS RICHARD DOW PAUL E. KELLY AT RNEY United States Patent E. I. du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Filed Aug. 2, 1966, Ser. No. 569,703 8 Claims. (Cl. l0224) ABSTRACT 0F THE DISCLOSURE An explosive booster which is desensitized after exposure to water by ingress of water through at least one aperture in the booster facilitated by a surfactant on at least one surface adjacent said aperture.

Previously, an explosive assembly for use underwater has been provided comprising an elongated cylindrical shell, a charge of an explosive composition within the shell, an elongated cap-well within the shell and embedded in the explosive charge, the cap-well having a tapered upper portion for frictional engagement with the inner surface of the shell, a thin film of an adhesive substance between the upper portion of the cap-well and the shell, and a retaining means for an initiator within the cap-well. This assembly is described in US. 2,909,121 (to Gernert, Phillippe and Ramsdell). This explosive assembly provides a reliable means of detonating blasting agents of a lower order-of-sensitivity in a wet or damp environment.

It is sometimes desirable to have a booster which will actuate under wet conditions but after prolonged exposure to water will be desensitized. Prior art boosters have not fulfilled this need. Therefore a need still exists for a blasting assembly, used in underwater detonation, such as in off-shore seismic exploration, underwater signaling, or underwater demolition, of low order-of-sensitivity explosives, which can be successfully actuated for a short time, e.g., 2-60 minutes, after being submerged in water but after a more prolonged exposure to water will become desensitized so that accidental initiation cannot occur should the assembly misfire and wash ashore.

This invention provides a water work booster 50 constructed that if it should fail to fire within a designated period of time its explosive charge will become desensitized by the action of water leakage into and distribution throughout the explosive component within the booster. To allow such leakage, at least one aperture is provided in the booster. This is preferably accomplished by providing a cap well with one or more grooves along the perimeter of its top section, one or more openings at the base of the cap-well or on its lateral surfaces, and a coating of a wetting agent on at least one surface adjacent to the above water admission apertures, i.e. the inner and/or outer surfaces of the cap-well, the inner surface of the shell, or the explosive charge adjacent to the capwell.

The cylindical shell of the explosive assembly, which can be made of bronze, aluminum, or any other suitable material, contains a charge of a conventionally used, water sensitive detonating explosive adjacent to the capwell, in an amount normally used for priming or boosting. Examples of water-sensitive explosives include cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), N-methyl- N,2,4,6-tetranitroaniline (tetryl), or cyclotetramethylenetetranitramine (HMX).

It is this body of explosive which must be desensitized by water in order to deactivate the booster. To accomplish this a cap-well with rolled edges is provided with an opening, preferably at its base extremity, and is pressed to a given height within the shell so that its rolled edges do not form a seal with the shell, and its grooved tapered top section, while providing a frictional type engagement with the inner wall of the assembly container, allows water to enter, with the aid of the wetting agent, into the portion of the shell containing the charge of detonating explosive. In another typical embodiment of this invention, Water leakage into the shell of the booster is accomplished by using a cap-well, again provided with one or more openings, preferably at its base extremity, which is undersized, thus allowing water to enter between its outer surface and the inner surface at the booster shell. Desensitization is then achieved upon absorption of a given weight percentage of water, this percentage varying with the type of explosive charge used.

In some embodiments of this invention the capwell can also have holes formed in the lower portion of its lateral walls in place of, or in addition to, the one at its base. These openings serve to increase the rate of water flow into the booster charge. As previously mentioned, at least one surface adjacent to the water admission apertures, i.e., the inner and/ or outer surfaces of the cap-well, the inner surface of the shell, or the explosive charge, is coated with a wetting agent. Preferably the cap-well, and often the cap-well and one or both of the other surfaces are coated. The coating need not be free of voids and uncoated areas, but preferably provides a substantially continuous path for the passage of water to the charge. Wetting agents which can be used include anionic, cationic, nonionic and amphoteric types whose solution dries to a film. Representative anionic surfactants are alkylaryl sulfonates, e.g. sodium alkaylnaphthalene sulfonate, sodium dodecyl benzenesulfonate; hydrocarbon sulfonates, e.g. sodium alkyl sulfonate; alcohol sulfonic esters, e.g. sodium lauryl sulfate, sodium stearyl sulfate; aliphatic alcohol phosphates, e.g. sodium alkyl phosphate, alkyl phosphate triethanolamine; aliphatic amide sulfonates, e.g. sodium stearyl amide methylet-hylsulfonate; alkyl esters of sodium sulfosuccinic acid, e.g. diamyl ester of sodium sulfosuccinic acid; and sodium dinaphthylmethane disulfonates. Representative cationic surface active agents are substituted amines, e.g. polyalkylene amine, solubilized polyoxyethylene fatty tertiary amine; pyridinium salts, e.g. lauryl pyridinium chloride, lauryl pyridinium bisulfate, tetradecylpyridinium bromide; alkyl ammonium salts, e.g. cetyltrimethylammonium bromide, alkyl dimethyl hydroxyethyl ammonium bromide, lauryl trimethylammonium chloride; alkyl dimethylamine acetate and substituted imidazoline. Nonionic wetting agents which are typical of those which can be used are alkylaryl polyether alcohols, fatty acid amine condensates, ethoxylated aliphatic amides, ethoxylated fatty acids, polyethylene glycol ethers, alkylaryl polyglycol ethers, and polyoxyethylene ethers. Examples of amphoteric wetting agents are fatty nitrogen dioarboxylates, long chain betaines, and anhydrous acids of dicarboxylic coconut derivatives.

It is obvious, therefore, that a choice of one or a combination of several of the variations by which water desensitization can be brought about enables the manufacture of a water work booster that can be actuated successfullyafter a certain period of exposure to water,

. ing rolled edges 8, and a hole'7" at its base is pressed A through the open end of container 6 into the explosive charge 5. A neoprene washer 3 is Contained within the cap-well 4 and a rigid washer 2 is inserted over washer 3. A number of stake crimps 1 are provided in the capwell to secure the rigid retainer washer 2 and rubbery washer 3 in the proper position at the top of the cap-well.

The explosive charge adjacent to the cap-well within the shell can be any water sensitive material but RDX is preferred in this invention because it is easier to desensitize. The degree of water needed to desensitize the booster depends on the nature of the explosive material used. For example, desensitization of RDX occurs when 14% moisture is absorbed by the explosive powder. The typical loadings in this invention are loose explosive powder over one or two waxed explosive pellets or all loose explosive powder. The preferred loading is two waxed RDX pellets covered by loose RDX powder. In all of the preceding typical loadings the explosive powder may or may not be coated with a wetting agent, again, depending on the rate of water entry into the explo ive charge and, therefore, the rate of desensitization that is desired, since the more surface coated the more rapid the desensitization.

The cap-well, in addition to the hole at its base, can also contain a series of one or more grooves, preferably 4 to 8, along its major perimeter as shown in FIGURE 1A, which is a top, planar view of the cap-well of FIG- URE 1. Approximately half the normal force fit area is undersized to provide a pathway for fluid to the major body of explosive. The grooves are of such depth as to provide a gap of at least 5 mils, and preferably 5-20 mils, between the cap-well and the shell when the booster is in its assembled state. The hole at the base of the capwell and/or the holes along its lateral walls are about from 50 mils in diameter to the inner diameter of the base of the cap-well, and preferably about from 94 to 125 mils, and provide a means of water entry to the explosive. A single hole at the bottom is preferred to a series of holes, e.g. 2-6, along the sides for ease of manufacturing using conventional assembly techniques. The cap-well with a hole at its base is conveniently pressed into the shell by a press pin so designed that it plugs the hole in the bottom of the cap-well during pressing and, when a force of approximately 250 to 300 pounds is applied to the pin, it compacts the powder a sufficient amount, i.e. an average density of 1.00-1.25 g./cc., so that after the pin is removed the explosive powder will not fall out through the hole in the cap-well yet when the assembly is subjected to water the powder will not be so dense as to prevent water entry at the hole. The cap-well preferably is pressed so that the space between the top of the capwell and the open end of the shell is approximately 30 to 125 mils, preferably 50-75 mils.

FIGURE 2 is a cross sectional view of another typical embodiment of this invention in which 6 designates a generally cylindrical shell containing a charge 5 of detonating explosive in a suitable amount. The cap-well 9 is undersized and has its large diameter cut down to an approximate heights of 125 mils. The cap-well 9 is provided with four ratchet-type retaining points 10 which grip the wall of the booster while the pin is withdrawn after pressing and which also serve to prevent the loosefitting cap-well 9 from falling out of the booster shell 6. A hole 7 is located at the base of the cap-well. A neoprene washer 3 and rigid washer 2 are contained within the cap-well and are secured in position by stake crimps 1 as is previously described. The cap-well 9 is preferably pressed so that the space between the top of the capwell and the open end of the shell is approximately 500 mils. The cap-well 9 is of an outer diameter such that the open space between it and the inner diameter of the shell 6 is approximately 5 mils.

A typical press pin for those embodiments of this invention using the undersized cap-well 9 consists of a cylindrical shank, appended to a larger diameter head, whose end is shaped into a conical form, the cone angle being approximately 60, as shown in FIGURE 3. FIGURE 3 is a cross-sectional view of the press pin in which 12 designates the cylindrical shank, 11 is the layer diameter head, and 13 represents the conically shaped end which plugs the hole in the base of the cap-Well during pressing. A similarly designed pin is used to press the grooved cap-well with rolled edges except that the end of the shank consists of a stepped conical portion as shown in FIGURE 3A which is a detailed drawing of the point of that press pin. In FIGURE 3A 14 represents a truncated conical section whose cone angle is about 60 from which is appended the conical point 15 whose cone angle is approximately 30. The rest of the press pin is essentlally as shown in FIGURE 3.

The cap-well, shell, or explosive powder, to be coated are rinsed in a solution of wetting agent, e.g. Duponol G (sodium lauryl sulfate), in water and are allowed to dry thoroughly before the parts are assembled. The solution used to coat the cap-well or shell is a 1-10%, preferably a 5%, by volume solution of wetting agent in water and the solution used to coat the explosive powder is a 0.5-3%, preferably a 1%, by volume solution of the same.

After the cap-well has been pressed into place, a washer of neoprene or any other rubbery material is placed within the cap-well. This washer has a central opening of a diameter slightly smallerthan the diameter of a conventional detonating device, such as a blasting cap. A rigid washer, of aluminum bronze, or any other suitable material, whose central opening is larger than that of the rubbery washer is placed over the rubbery washer to retain and support the latter. The entire assembly is then crimped into position at a point immediately above the metal washer.

The following examples will illustrate the performance of this invention.

Example 1 A number of water work boosters are assembled as in FIGURE 2. These boosters are designed to function normally after up to one hour exposure in up to 23 feet of sea water and to become completely desensitized after 17 hours exposure to 10 feet of sea water. The tubular shells 6 are made of aluminum and have an outer diameter of 630 mils. The shells are previously rinsed in a 5% by volume solution of Duponol G in water and are allowed to dry thoroughly. The shells 6 are loaded with a charge 5 consisting of two waxed RDX pellets (each 750 mils long, 620 mils in diameter and containing 5.25 grams of waxed RDX) over which is loaded 9.0 grams of loose plain, unwaxed RDX powder. A hole 7 approximately mils in diameter is punched in the center of the base extremity of an aluminum cap-well 9 which has an undersized major diameter of 620 mils, the upper portion of the cap-well being 125 mils in height. The cap-well is then treated similarly to the shell 6 by rinsing it in a 5% by volume solution of Duponol G in water and allowing it to dry completely. The cap-well 9 is inserted into the shell and is pressed so that the space between the top of the cap-well and the open end of the shell is approximately 500 mils. The cap-well, being undersized, fits loosely in the shell thus allowing water to enter in the void between the cap-well and shell and to reach the explosive material. A neoprene washer 3 with a central opening of 260 mils is placed within the cap-well after pressing is completed and an aluminum washer 2 whose central opening is 320 mils is placed on top of the neoprene washer. The assembly is then crimped together. The boosters are subjected to 10 feet of sea water for various lengths of time, the sea water being contained in a steel pipe standing vertically in a 10 foot well. Boosters are tested by attempting actuation thereof after predetermined exposures with seismograph instantaneous electric blasting caps. The results are summarized in the table below.

TABLE 1 Sea Water No. of No. 01 N o. of N o. of Exposure Time Depth Tests Detonations Partial Failures (ft.) Detonations 10 11 ll. 0 10 4 3 l 0 10 6 1 0 5 10 2 0 8 10 8 1 0 7 10 8 0 0 8 By partial detonation is meant that some of the loose powder shot but the pellets were not initiated.

Example 2 of aluminum. These shells 6 are loaded with a charge 5 of two waxed RDX pellets over which is loaded 9.0 grams of RDX powder treated with a 1% solution of Duponol G and allowed to dry completely. The capwell 4 has a series of 8 grooves along its major perimeter, approximately half this perimeter being undersized thusly, and a hole 7 of 125 mils in diameter punched in A series of 100 boosters, 25 in each group, are assembled and tested similarly as in Example 1 with the following modifications:

In Group 1 an uncoated shell, uncoated cap well and 8.0 grams of coated powder are used.

In Group 2 an uncoated shell, coated capwell and 8:0 grams of Coated powder are used 90 the approximate center of its base extremity. The cap- In Group 3 a coated Shell Coated n and SD well is rinsed in a 5% by volume solution of Duponol grams f uncoated powder are used G in water and is allowed to dry thoroughly. After in- In Group 4 a coated shell, coated cap-well and 8.0 seftlhgcaprweh 4 n Shell 6, the pis Pressed at grams f coated powder are d approximately 250 pounds force on the special afore- The boosters are subjected to 10 feet of sea water he mentioned press pin so that the space between the rolled fore testing and the results are as follows. edges of cap-well 4 and open end of shell 6 is approxi' TABLE 2' Group 1 Group 2 Group 3 Group 4 Exposure Time D PD F D PD F D PD F D PD F 3 0 2 3 0 2 3 o 2 1 2 2 1 0 4 1 0 4 1 0 4 3 0 2 1 o 4 o 0 5 0 0 5 o o 5 o 0 5 0 0 5 0 o 5 1 0 4 24hours 1 0 4 0 0 5 1 0 4 0 0 5 D=number oi detonations, PD=number of partial detonations, and F=number of failures.

Example 3 mately 65 mils. A neoprene washer 3 and rigid washer 2 40 are inserted and crimped into place by stake crirnps 1 A number of boosters are assem l d nd t d as in as described in Example 1. The boosters are also tested Example 1 With the exception that the Shell of the blastas described in Example 1. After the boosters withstand ihg assembly is not Subjected to Coating y a Solution of a 24 hour exposure to 10 feet of sea water and are tested, a wetting agent although the cap-Well is SO c d. These there are four failures out of four trials, indicating deboosters are designed to function normaly after up to 5 sensitization is complete. minutes exposure to 10 feet of sea water, to become partially desensitized after up to 30 hours exposure and to Example 5 become completely desensitized after 30 hours exposure A number of boosters are assembled and tested as in to 10 feet of sea water. The results are tabulated below. the proceeding example except that 13 grams of Du- TABLE 3 Sea Water N o. oi N o. of N 0. or No. of Exposure Time Depth (17.) Tests Detonations Partial Failures Detonatious 10 3 3 o 0 10 4 3 o 1 10 s 3 1 4 1o 4 o 1 3 For comparative purposes, a number of boosters are ponol G treated loose RDX powder is used in place of assembled and tested as described in Example 1 except the 9.0 grams coated RDX powder and two waxed RDX that no wetting agent is used to coat any part of the aspellets. After 17 hours exposure to 10 feet of sea water sembly. Thus the booster consists essentially of a plain there are five failures out of five trials. cap-well, plain shell, and uncoated RDX powder. The resulting explosive assemblies, after being exposed to 10 Example 5 feet of sea water for 65 hours have 10 detonations out of 10 trials and are, accordingly, not desensitized. Eight boosters are assembled as in Example 4 except 4 that the cap-well has a series of 4 grooves along its major Example perimeter instead of 8 grooves, the 4 grooves being of A number of boosters are assembled as shown in FIG- such a depth so that half the normal force fit area re- URE 1. These boosters are designed to function normally mains undersized, 9.0 grams of RDX powder which is after up to 5 minutes exposure to 10 feet of water, after previously treated with a 1% solution of Duponol G which time partial densensitization takes place until after in water is loaded over a wood dowel in place of two 17 hours exposure complete densitization occurs. The waxed RDX pellets, and a bronze shell, not treated with tubular shells 6 are 630 mils in diameter and are made a wetting agent, are used. The results are tabulated below.

TABLE 4 Sea Water N0. of No. of No. of N0. of Exposure Time Depth (ft.) Tests Detonations Partial Failures Detonatlons 2 hours 23 2 0 2 4 hours 10 2 0 0 2 17 hours. 10 2 0 0 2 24 hours. 10 2 0 0 2 Similar results are obtained in all of the above examples by using other Wetting agents, e.g. sodium stearyl sulfate, sodium dodecylbenzene sulfonate, lauryl trimethylammonium chloride, or polyethylene glycol lauryl ether, in place of Duponol G.

It can be concluded from the foregoing examples that this novel explosive assembly provides a water work booster which can be used reliably underwater to detonate low order-of-sensitivity explosive materials for a period of 5 minutes to one hour after submergence, but which, after a longer exposure to water, will become desensitized thus eliminating the possibility of an accidental actuation should the booster be Washed ashore.

We claim:

1. In a booster comprising a shell, a cap-well within and in engagement with said shell, and an explosive charge adjacent to said cap-well, the improvement which comprises providing at least one aperture in the booster for admission of water to said explosive charge, and at least one surface adjacent to said aperture bearing a wetting agent, said explosive charge adjacent said aperture being water sensitive.

2. The booster of claim 1, wherein an aperture is provided in the base of the said cap-well.

3. The booster of claim 2, wherein the outer diameter of the top section of said cap-well is at least 10 mils less than the inner diameter of said shell.

4. The booster of claim 2 wherein at least one groove running longitudinally through the area of engagement of said shell and cap-well is provided along the perimeter of the top section of said cap-well.

5. The booster of claim 4 wherein the surface of said cap-well is coated with a wetting agent.

6. The booster of claim 4 wherein the inner surface of said shell is coated with wetting agent.

7. The booster of claim 4 wherein said explosive charge contains wetting agent.

8. The water work booster of claim 4 wherein the surface of said cap-well, the inner surf-ace of said shell, and said explosive charge are coated with sodium lauryl sulfonate, said aperture having a diameter of about to mils, and wherein the separation between the said cap-well and said shell in said grooves is about 5 to 20 mils.

References Cited UNITED STATES PATENTS 3,279,372 10/1966 Patterson 102-28 3,322,066 5/1967 Grifiith et a1. 102-24 SAMUEL FEINBERG, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner.

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