Secondary explosive

The amounts of primary initiator needed to detonate a secondary explosive vary from 10 to 400 mg and depend on both components. The major requirements of a good initiator are that it must be sufficiently stable for safe manufacturing, compatible with metal casing, easily loaded into detonators, and not too expensive. Its storage under adverse conditions must not alter its properties or stability. 

The initiators are sensitive to friction and shock (blow). The percussion sensitivity is measured by the drop-hammer method where a 2 kg steel ball is dropped from increasing heights tmtil detonation occurs. The amount of electrical energy needed to initiate the detonation depends on the initiator. 

Diazodinitrophenol, though sensitive to impact, is not as sensitive to friction or electrostatic energy but somewhat less stable to heat than lead azide. 

Lead styphnate (CsHNsOgPb), or lead trinitroresorcinate, is very sensitive to electrostatic discharge and often used to sensitize lead azide. 

Tetrazene (C2HgNioO) is readily decomposed in boiling water and is usually used as an ignition agent for lead azide. It is very sensitive to percussion and friction. 

Primary explosives differ considerably in their sensitivity to heat and in the amount of heat they produce on detonation. The heat and shock on detonation can vary but is comparable to that for secondary explosives. Their detonation velocities are in the range of 3500-5500 ms-1. 

Primary explosives have a high degree of sensitivity to initiation through shock, friction, electric spark or high temperatures and explode whether they are confined or unconfined. Typical primary explosives which are widely used are lead azide, lead styphnate (trinitroresorci-nate), lead mononitroresorcinate (LMNR), potassium dinitrobenzo-furozan (KDNBF) and barium styphnate. Other primary explosive materials which are not frequently used today are mercury azide and mercury fulminate. 

Secondary explosives (also known as high explosives) differ from primary explosives in that they cannot be detonated readily by heat or shock and are generally more powerful than primary explosives. Secondary explosives are less sensitive than primary explosives and can only be initiated to detonation by the shock produced by the explosion of a primary explosive. On initiation, the secondary explosive compositions dissociate almost instantaneously into other more stable components. An example of this is shown in Reaction 2.4. 

Some secondary explosives are so stable that rifle bullets can be fired through them or they can be set on fire without detonating. The more stable explosives which detonate at very high velocities exert a much 

Examples of secondary explosives are TNT, tetryl, picric acid, nitrocellulose, nitroglycerine, nitroguanidine, RDX, HMX and TATB. Examples of commercial secondary explosives are blasting gelatine, guhr dynamite and 60% gelatine dynamite. 

Secondary explosives (also known as high explosives) differ from primary explosives in that they cannot be detonated readily by heat or shock and are generally more powerful than primary explosives. Secondary explosives are less sensitive than primary explosives and 

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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... 

Proper ventilation and housekeeping minimizes secondary explosions. Dust coUectors of the dry type should be located outside the building, and provided with conduction bags and adequate explosion venting to a safe location. 

The hot gases expand and produce pressure waves, which 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. 

That this is not always the case should be expected. In fact, if it was not for heterogeneous localization of some flow phenomena, it would be very diflicult to initiate secondary explosives, or to effect shock-induced chemical reactions in solids. Heterogeneous shear deformation in metals has also been invoked as an explanation for a reduction in shear strength in shock compression as compared to quasi-isentropic loading. We present here a brief discussion of some aspects of heterogeneous deformation in shock-loaded solids. 

The fact that hot spots are required for explosive initiation can be seen by calculating for the bulk temperature, say 350 K, and the anticipated hot-spot temperature, say 700 K. We take typical values of Arrhenius constants for secondary explosives QjCp 2500 K, //c = 25,(X)0 K, and V = 10 s V Hence... 

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. 

Good housekeeping, particularly to avoid a devastating secondary explosion. 

High explosives which detonate to produce shock waves. Materials which are easily detonated by mechanical or electrical stimuli are termed primary explosives . Those requiring an impinging shock wave to initiate them are secondary explosives . 

Good housekeeping, particularly to avoid a devastating secondary explosion, following redispersion of any accumulations of combustible dust. 

High explosives (sometimes called secondary explosives). 

Detonator. A metal tube containing a primary explosive used for initiating a secondary explosive. 

Secondary explosive. Alternative name for high explosive indicating that the explosive does not burn to detonation but is detonated by suitable devices. 

It is a treacherously sensitive, very brisant primary explosive (while its cobalt analogue is a well behaved secondary explosive). 

Very frequently an incendiary effect follows the explosion, setting fire to the debris, especially if gasoline, oil, or metals are used as the secondary explosion material. 

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,... 

Figure 14. A secondary explosion of the accumulated dust in passage ways and galleries by a minor initial explosion can propagate throughout a plant with devastating results.

An initial dust explosion can cause secondary explosions. The primary explosion sends a shock wave through the plant, stirring up additional dust, possibly resulting in a secondary explosion. In this fashion the explosion leapfrogs its way through a plant. Many times the secondary explosions are more damaging than the primary explosion. 

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. 

The influence of the vent duct upon the pressure increase is most pronounced when the flame propagation from the secondary explosion in the vent duct reaches the velocity of sound. This is valid for vent ducts of... 

Attempt to identify agent or weapon, type of dissemination (aerosol/liquid/vapor/solid), and characteristics of the agent and threats posed. Search the area for secondary explosive devices or booby-traps designed to kill or maim first responders. Limit the number of personnel and exposure time on scene. 

Secondary explosives, 10 722, 724 Secondary fibers, bleaching of, 21 51-52 Secondary fixed points, Tgo values for,... 

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