Initiation detonators

Fig. 3.2. Controlled, high pressure shoek loading ean be routinely earried out with large diameter plane wave explosive lenses whieh initiate Detonation in cylinders of high explosives with known, reproducible behavior. Detonation waves from the explosive are transmitted into metal plates which can serve as standards and on which samples to be studied are placed.

Several studies have shown that the shock sensitivity of granular expls depends on expl particle size. The consensus is that the threshold shock pressure to initiate detonation in a given expl is less for large particles than for small particles. However, the converse is true when one considers run-up distances (or run-up times) to detonation. Thus at some pressure above the threshold for both large and small particles, run-up to detonation is smaller for small particle charges than for large particle charges... 

A violent explosion of Picric Acid in a Manchester factory in 1887 was ascribed to the formation of picrates. Burning, molten Picric Acid flowed down onto lithopone, forming lead picrate which in consequence caught fire. The latter, being an initiator, detonated and caused the Picric Acid to detonate... 

Threshold shock pressures to initiate detonation in several SP are shown in Table 55. In general, unless the SP contains solid HE ingredients such as HMX or RDX, the threshold pressures are considerably greater than for solid HE at a comparable degree of compaction. Even so, the pseudo-composites of AP/wax must be considered to be rather shock-sensitive provided their degree of compaction does not exceed about 90% of their theoretical max density (TMD), Figure 21 shows that up to about 90% TMD the shock sensitivity of an 80/20 AP/wax composite is very similar to that of TNT... 

Temperature field obtained by numerical simulations [23] behind the front of a fully developed (0.3 ms after the detonation initiation) detonation in hydrogen/air at 1 atm. Minimum computational cell size is 5 pm. (Courtesy of V. Gamezo.)... 

The sensitiveness of an explosive to impact is measured by determining the minimum height from which a given weight must be dropped in order to initiate detonation. Many forms of fall hammer test have been devised, the most important point of the various designs being the means adopted for retaining the explosive. A simple and practical method, used at Ardeer for many years, is shown in Fig. 6.7. In this the explosive is put... 

The cyanide is a friction- and impact-sensitive explosive, and may initiate detonation of liquid hydrogen cyanide. Other heavy metal cyanides are similar. 

It is, like copper(II) azide, an exceptionally powerful initiating detonator, containing 61.5% of nitrogen. 

Decomposition of a 70% nitric acid-ammonium nitrate slurry explosive led to overflow, contact with wood and a fire. This spread to detonators, which initiated detonation of the slurry. 

Lead azide, on prolonged contact with copper, zinc or their alloys, forms traces of the extremely sensitive copper or zinc azides which may initiate detonation of the whole mass of azide. 

M. Held, Initiierung von Sprengstoffen, ein vielschichtiges Problem der Deto-nationsphysik, Explosivstoffe 16, 98-113, (1968) und J. Jaffe, R. Beaugard und Amster. Determination of the Shock Pressure Required to Initiate Detonation of an Acceptor in the Shock Sensitivity Test - ARS Journal 32, 22-25 (1962). 

Slurry explosives consist of saturated aqueous solutions of ammonium nitrate with sensitizing additives.[i-3] Nitrates such as monomethylamine nitrate, ethylene glycol mononitrate, or ethanolamine mononitrate are used as sensitizers. Aluminum powder is also added as an energetic material. Table 4.15 shows a typical chemical composition of a slurry explosive. It is important that so-called micro-bubbles are present within the explosives in order to facilitate the initial detonation and the ensuing detonation wave. These micro-bubbles are made of glass or polymeric materials. 

Pyrolants deflagration detonation gas generators, igniters, fireworks, squibs, safety fuses detonators, primers, initiators, detonating fuses... 

Support was found for the hypothesis that the deton wave initiates deton in the neighboring layer of the intact expl by the discontinuity of material velocity which it produces. This acts like a very vehement mechanical blow — a mass-velocity of approx 1500 m/sec — and is probably more effecting at high temp... 

The velocity of advance of the front is super sonic in a detonation and subsonic in a deflagration. In view of the importance of a shock process in initiating detonation, it has seemed difficult to explain how the transition to it could occur from the smooth combustion wave in laminar burning. Actually the one-dimensional steady-state combustion or deflagration wave, while convenient for discussion, is not easily achieved in practice. The familiar model in which the flame-front advances at uniform subsonic velocity (v) into the unburnt mixture, has Po> Po> an[Pg.249]

F) I. Jaffee et al, AmRocketSocJ 32, 22-5 (1962) CA 56, 11872(1962) (Shock pressure required to initiate detonation of an acceptor in the shock sensitivity test)... 

Dunkle (Ref 3) made the following r emark "I hate to disagree with Cook, but I would call a detonation propagating at less than sonic velocity a deflagration. Evidently the wave sets up sound waves ahead which go at successively faster rates, thus telescoping into a shock wave which initiates detonation some distance ahead of the low-velocity wave ... 

The pressure "jump necessary to initiate detonation in various expls does not belong under this heading. This has been discussed under "Detonation (and Explosion Initiation - - - - in Explosive Substances . The actual value of the required "jump seems to be 25-50 atm (Ref 9). 

AND EXPLOSION), EXPERIMENTAL PROCEDURES . Determination of shock pressure required to initiate detonation of an acceptor in the shock sensitivity test is described in Ref 8 Refs 1) W.C. Holton, "The Detonation Pressure in Explosives as Measured by Transmitted Shocks in Water , NavOrdRept 3968(1954) (Conf) 2) Dunkle s Syllabus (1957-1958), p 175 3) Cook (1958), 68-9... 

Jaffe et al (Ref 3), in the course of determination of the shock pressure required to initiate detonation of an acceptor in the shock sensitivity test, found that the velocity of the front as sensed by the pressure probe method, falls behind the true velocity of the shock front as the shock is attenuated. It has also been found that the maximum transmitted shock velocity generated by the two Tetryl pellets and measured in Lucite is 4.6mm/frsec. Shock velocities determined by optical method, shown in Table 3, p 25, run between 2.701... 

Abel assumed that molecules of each.expl vibrate during deton and thus incite vibrations of the surrounding medium at a frequency characteristic for each. expl. The particles of the medium spread in all directions and, if another charge of the same expl is in the neighborhood, its particles start to vibrate in resonance and thus might initiate deton. This was an explanation of the phenomenon known now as "detonation by influence or "sympathetic detonation . The propagation of deton in condensed expls was assumed to be caused by. spread of vibrations in resonance with particles inside the expl. This theory was abandoned in 1883 in favor of the Berthelot Theory of Detonation, which is briefly described in Vol 2 of this Encycl, p B106-L. Berthelot s Theory was further developed by. P. Vieille... 

The simplest primer of this type is shown in Fig 1-34 copied from Ref 17, Fig 13 on p 47. This primer cannot be used to detonate delay columns but is suitable for initiating detonators... 

Fuze, Antiwithdrawal. A fuze incorporating a device intended to initiate detonation of an item of ammunition if attempt is made to remove the fuze from the item... 

Bomb fuzes are devices used to initiate detonation of aerial bombs... 

In the present volume, the authors have attempted to give a systematic and coherent account of the experimental phenomenology of the initiation, detonation, and physical effects of detonating high explosives. In ever-increasing quantities, explosives are used both in rock blasting and in an increasing number of new and unorthodox technical processes. 

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