Sympathetic detonation

Detonation, Sympathetic Detonation. Flash over means the transmission of detonation from a cartridge to another one in line. Explosives with extremely high flash over tendency can be initiated by the shock wave from one charged borehole to the next one, even at large distances (- Ditching Dynamite). 

It has been found that upon detonation, an explosive can cause a nearby sample of explosive to detonate sympathetically. The distance over which one charge can detonate another is a function of the amount of energy produced by the first explosion and the medium through which the shock wave is propagated to the second charge of explosive. For instance, the relationship for air (very approximately) would be expected to be weight of explosive in lbs/(distance in ft)3 = 4. Thus, to calculate the maximum distance for a possible sympathetic detonation of 40,000 lbs of explosive, the calculation is ... 

Detonation, Sympathetic Detonation. Flash over means the transmission of detonation from a cartridge to another one in line. Ex-... 

Two common explosive materials are Primacord and Detasheet. PETN is the explosive core of Primacord, where it develops a velocity rate of 6,400 metres per second. Primacord is insensitive to friction and ordinary shock, hut may be exploded by rifle fire. It also detonates sympathetically with the detonation of an adjacent high explosive. Odours from Primacord thermostated at 60° C were tested and the organic compounds detected confirmed the presence of only PETN as shown in Figure 10. 

The criteria for insensitive explosives subjected to ha2ard tests permit no reaction more violent than burning in slow and fast cook-off tests and fragment and bullet tests, no propagation in sympathetic detonation tests, no detonation when stmck by a shaped charge jet, no sustained burning when hit by a small fragment, and such special tests as may be required by the use of the explosive. 

There is a drive to develop insensitive or less sensitive munitions, ie, those less likely to accidental or sympathetic detonation. A leading candidate is 3-nitro-l,2,4-triazolin-5-one [930-33-6] (59), made by the reaction of semicarbazide and formic acid to give l,2,4-triazolin-5-one [932-64-9] foUowed by nitration of the triazolone (218). 

Bull, D. C., J. E. Elsworth, M. A. McCleod, and D. Hughes. 1981. Initiation of unconflned gas detonations in hydrocarbon-air mixtures by a sympathetic mechanism. Progress in Astronautics and Aeroruiutics. 75 61-72. AIAA Inc., New York. 

In the manufacture of high explosives, the possibility of accidental detonation must always be borne in mind and buildings are constructed and arranged so as to minimise the possible effects of such an explosion. The buildings are placed sufficiently far apart so that an explosion in one building will not cause sympathetic detonation in the other. Practical distances do not make it completely impossible for detonation in one house to leave all other houses unaffected, for two reasons ... 

Card-Gap Test for Determination of Sympathetic Detonation. See under Detonation by Influence and also Refs 40, 47, 48, 54 58 under Detonation, Experimental Procedures... 

Detonation, Carry-Over Distance in Sympathetic Detonation. The term "carry-over distance is used by Evans in the examination of phenomenon called by him "Transition of... 

Burning , etc are listed in Vol 1, p IX Calorimetric Tests for Explosives, Propel- Coefficient de self-excitation (CSE). Fr test for sympathetic detonation. See Vol 3, p C390-L... 

Detonation by Influence or Sympathetic Detonation Tests. Several tests are listed in Vol 1, p X and their description is given in this Section under "Detonation (and Explosion) by Influence ... 

GAP TESTS. A general name for several tests used for determination of sympathetic detonation. They include Bur of Mines tests "Halved-Cartridge Method (Vol 1, p XIV), French "Coefficient de self-excitation ... 

Sympathetic Detonation Tests. See under Detonation by Influence... 

Accdg to Dunkle (Ref 29) "Sympathetic detonation must be due to shock waves in air, which produce a pressure wave in the receptor charge on striking it. Such shock waves are much stronger in the direction in which the detonation has been propagating ... 

More detailed explanation of the phenomenon of sympathetic detonation is given by Robinson in Ref 10b, p 16 and by Rinken-bach in Ref 13, p 67. Accdg to them ... 

If the chges are unconfined the detonating wave of donor moves out in all directions, its energy presumably decreasing as its spherical volume increases. Since the vol of a sphere is proportional to the cube of the radius, it was assumed that the weight (W) needed to initiate sympathetic deton would vary as the cube of the distance (L). 

In actual practice, however, the equation W/L =k does hold as good as the equation W/L =k, proposed by F.A. Olsen. The constant k is different for each combination of expls. The fact that the relation W/L3 does not fit experimental results, indicates that the sympathetic deton phenomenon depends not only on the weight but also on other factors. These factors might include strength (as mentioned before), detonation velocity, density of charge, sensitivity of receptor, etc... 

As has been mentioned already, the sensitiveness to influence is lower when media other than air are used. There are tests specially designed for using wax as a barrier, such as the wax-gap test of Spencer Chem Co described in Vol 1 of Encycl, p A354, footnote c and the booster sensitivity test described in Vol 1, p VIII Other methods for detg sympathetic detons include ... 

SS 16, 9-10, 25-7 35-7(1921) (Detonations-iibertragung brisanter Sprengstoffe) 4) Anon, Army Ordn 3, 180-82(1922) (Sympathetic deton tests of HE shells) 5) C.G. Storm, ArmyOrdn 3, 256-60(1923) (Sympathetic detons) 6) G. St. Perrott D.B. Gawthrop, JFrankllnst 203, 103 8t 387-406 (1927) (Propagation of deton betw two cart-... 

Loehr (Deton by influence) 14a) J. Savitt, "Investigation of Sympathetic Detonation and Evaluation of Structures for Ammunition Manufacture , Final Rept, ArmourRes-FoundationCenter, 20 Oct 1955 (Contract DA-11-173-ORD-416) 15) T. Watanaba St... 

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