Secondary explosives ignition

It follows from Table 8.18 that the sensitivity of l-(l//-tetrazol-5-yl) guanidinium nitrate is relatively low, similar to secondary explosives. Ignition of l-(l//-tetrazol-5-yl)guanidinium nitrate takes place at 186 °C and the DSC onset is at 163 °C (10 °C min ) [52]. 

Ethylenedinitramine (EDNA) is a powerful secondary explosive patented by Hale [3]. The two acidic hydrogens of the nitramino group can be relatively easily replaced with metal ions. Every once in a while speculation arises regarding the applicability of EDNA salts for use as primary explosives. The sensitivity of the metallic salts is, however, relatively low. The cupric salt of ethylenedinitramine is less sensitive than both LA and LS. It follows from Table 13.2 that it is comparable to secondary explosives. Ignition of CuEDNA occurs at 196 °C, DSC onset is at 162 °C (10 °C min ) [4]. Cupric, ferrous, lead, and potassium salts of EDNA are more sensitive then RDX but not sensitive enough to qualify for use as primary explosives. Impact sensitivities obtained by Blatt [5] and summarized in Fedoroff, Shefield, and Kaye s [6] are listed in Table 13.3. 

Dust explosions usually occur in pairs. The first explosion involves dust already in suspension. This jars dust from beams, ledges, etc, creating a second cloud to which the explosion propagates, resulting in a secondary explosion. Dust clouds have been ignited by open flames, electric sparks, hot... 

Dust explosions are relatively rare but ean involve an enormous energy release. A primary explosion, involving a limited quantity of material, ean distribute aeeumulations of dust in the atmosphere whieh, on ignition, produees a severe secondary explosion. 

If a dust or powder is to be used for the secondary explosion, the explosive/incendiary initiator may be enclosed in any sort of a packet and placed within or under the material to be dispersed and ignited. See Figure 62. If the initiator is to be used in gasoline or fuel it will have to be enclosed... 

Electrostatics enters into the problem of secondary explosions in several ways. First, an electrostatic spark may be the ignition source of the primary explosion. Second, an electrostatic spark can serve to ignite a dust cloud if particulate spews out at high velocity as a result of a sudden piping or vessel containment failure. Similar containment failures have occurred with insulating liquids and can not be ruled out for powders. For example,... 

Dust presents a different type of hazard, because while it has a lower explosive limit, it does not have an upper explosive limit. This can result in a primary explosion, followed by secondary explosions as new air is provided. Secondly, dust does not diffuse away from its point of release, but settles out of the air and accumulates into layers. Unlike vapor, the dust explosion is caused by the radiant heat from one particle igniting the next. Because of this, the lower explosive limits for dusts are greatly higher than for vapors. Also, the size and shape of the dust particles are important factors in effecting its lower explosive limit. 

In a special publication devoted to sulfide ore dust explosions, a dust explosion in a copper-zinc sulfide mine is discussed and related to causes and preventive measures [1]. Control measures [2] and prevention of secondary explosions are also discussed [3], and surveyed, including the need for further work [4], The results of experimental work on the use of limestone dust to suppress explosions in pyrites dusts are presented [5], For another special publication on ore dust explosion with numerous incidents and further studies on mechanism and control see [6], Explosibility declines in the order pyrrotite, pyrite, chalcopyrite, sphalerite, covellite, chalcocite, galena. Pyrite at 1000 g/m3 can give a peak pressure of 5.8 bar [7], Self heating of broken sulfide ore, to possible ignition, has been studied. Pyrrhotite seems primarily responsible [8],... 

To achieve high-order detonation in secondary explosives, it has always been necessary to allow much longer delays in order to let the low-order process initially started "jump to high order [Compare with Detonation (and Explosionjby Influence] Note 2 In a review of 23 papers on initiation, ignition, and growth of reaction presented at the 4thONRSympDeton bv G.P. 

Secondary explosives will burn without detonating if unconfined or lightly confined. Some secondary explosives, such as PETN, are difficult to ignite and propagate burning only at slightly elevated ambient pressures... 

Italian Incendiary Shell. Italian antiaircraft incendiary pellet projectiles, in WWlI, consisted of a 76 or 90-caliber shell loaded with a number of incendiary-filled cylindrical pellets. The pellets were ignited by a flash from a central flash tube. A delay mixture activated a secondary explosive in the base which broke the shell into flak. Composition of the incendiary filling is not given in Ref 16... 

Explosives can therefore be classified by the ease with which they can be ignited and subsequently exploded. Primary explosives are readily ignited or detonated by a small mechanical or electrical stimulus. Secondary explosives are not so easily initiated they require a high velocity shockwave generally produced from the detonation of a primary explosive. Propellants are generally initiated by a flame, and they do not detonate, only deflagrate. 

Belyaev s experimental studies related to liquid secondary explosive materials—methylnitrate, nitroglycol, nitroglycerine—and to secondary explosive materials which are solid at room temperature, but which melt when ignited—trotyl, picric acid, etc. 

Secondary explosives, or high explosives, are generally less sensitive to heat and shock than primary explosives and are therefore safer to manufacture, transport, and handle. Most secondary explosives will simply burn rather than explode when ignited in air, and most can be detonated only by the nearby explosion of a primary initiator. Among the most common secondary explosives are nitroglycerin, trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), and RDX. 

Explosives are classified as primary or secondary, based on their susceptibility to initiation. Primary explosives, which include lead azide and lead styphnate, are highly susceptible to initiation. Primary explosives often are referred to as initiating explosives because they can be used to ignite secondary explosives. Secondary explosives, which include 2,4,6-trinitrotoluene (TNT), hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX or cyclonite), high melting explosives (HMX) like octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazine (HMX),... 

Primary ignition refers to the concept that a tiny bit of relatively unstable, high-intensity explosive can be used safely to detonate relatively stable explosive compounds. If a primary ignition system is used, waxes and clay can be added to sensitive secondary explosives to stabilize them for transportation and deployment. Then very fast, easily detonated mixtures can be used in very small amounts to make the whole batch go. In some cases, two booster stages are employed, leading to final detonation of the main explosive charge. This is, in fact, what occurs when commercial powder handlers use a cap to detonate primer cord which, in turn, is wrapped around a block or more of C-4. 

Many combustible dusts produced by industrial processes are explosible when they are suspended as a cloud in air. Even a spark may be sufficient to ignite them. After ignition, flame spreads rapidly through the dust cloud as successive layers are heated to ignition temperature. The hot gases expand and produce pressure waves that travel ahead of the flame. Any dust lying on surfaces in the path of the pressure waves will be thrown into the air and could cause a secondary explosion more violent and extensive than the first. 

Sensitivity Easily ignited Classification Secondary explosive... 

DNAN forms colorless crystals with a melting point of 120 Celsius. It is fairly soluble in hot water, hot ethanol, methanol, and acetone. It is less soluble in cold water, cold ethanol, and insoluble in chloroform, benzene, ether, and petroleum ether. DNAN is somewhat hygroscopic, and moisture slowly decomposes it—should be stored in a desiccator. A small sample bums leaving a residue of carbon when ignited—a small sample can be detonated by the blow of a hammer. DNAN can be used in explosive compositions when alloyed with TNT, or other low melting secondary explosives, gun propellants with nitrocellulose, nitro starch, or nitroglycerine, and rocket propellants when mixed with ammonium perchlorate. DNAN also demonstrates usefulness for priming mixtures with lead azide, lead styphnate, or diazodinitrophenol, and for use in fireworks. ... 

Electrostatic ignition is difficult with secondary explosives. 

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