Initiation accidental

Safety has been greatly increased by use of the continuous nitration processes. The quantity of nitroglycerin in process at any one time is greatly reduced, and emulsification of nitroglycerin with water decreases the likelihood of detonation. Process sensors (qv) and automatic controls minimize the likelihood of mnaway reactions. Detonation traps may be used to decrease the likelihood of propagation of an accidental initiation eg, a tank of water into which the nitrated product flows and settles on the bottom. 

Calcium Hypochlorite. High assay calcium hypochlorite [7778-54-3] was first commercialized in the United States in 1928 by Mathieson Alkali Works, Inc. (now Olin Corp.) under the trade name HTH. It is now produced by two additional manufacturers in North America (Table 5). Historically, it usually contained about 1% water and 70—74% av CI2, so-called anhydrous product, but in 1970, a hydrated product was introduced (234). It is similar in composition to anhydrous Ca(OCl)2 except for its higher water content of about 6—12% and a slightly lower available chlorine content. This product has improved resistance to accidental initiation of self-sustained decomposition by a Ht match, a Ht cigarette, or a small amount of organic contamination. U.S. production in the 1990s consists primarily of partially hydrated Ca(OCl)2, which is sold as a 65% av CI2 product mainly for swimming pool use. Calcium hypochlorite is also sold as a 50% av CI2 product as a sanitizer used by dairy and food industries and in the home, and as a 32% product for mildew control. 

The chance of accidental initiation is related to the energy imparted to the substance and the sensitivity of the compound. Hence the sensitivity of compounds should be established (e.g. Table 7.15) before devising appropriate control measures. (Many sensitive explosives have ignition energies of 1-45 m, while some very sensitive materials have ignition energies <1 m. )... 

Initiation Characteristics. Usually the initiation characteristics of an expl are examined from two different points of view, namely, how to obtain reliable initiation, and how to avoid accidental initiation. It is the latter point of view that we will emphasize, since, as stated at the beginning of this section, there is no problem in initiating PETN reliably. Conversely, PETN, because of its sensitivity , is prone to accidental initiation. We will now proceed with the description of various modes of initiation of PETN, For general modes of expl initiation see Vol 7,1106-109... 

ESD systems should be designed to be sufficiently reliable and fail safe that a (1) accidental initiation of the ESD is reduced to acceptable low levels or as low as reasonably practical, (2) availability is maximized as a function of the frequency of system testing and maintenance, and (3) the fractional MTBF of the system is sufficiently large to reduce the hazard rate to an acceptable level, consistent with the demand rate of the system. 

Extremely insensitive articles which do not have a mass explosion hazard. The articles contain only extremely insensitive detonating substances and demonstrate a negligible probability of accidental initiation or propagation. 

Although the Regulations are both extensive and detailed, sound advice will be found on matters such as firework fusing and the prevention of accidental initiation which might occur e.g. 

The explosive was exhaustively characterized for thermal behavior, impact sensitivity and electrostatic discharge sensitivity etc. Based on this data, CP has been described as much less sensitive to accidental initiation than primary explosives such as LA but at the same time, initiation grows rapidly to detonation when properly confined. Its performance evaluation in a test detonator or hardware indicates that CP can replace primary explosives in many hot wire detonator applications especially if safety considerations are of prime importance [239]. 

Electro-Explosive Devices (EED s) Operational Safety. It is known that EED s are sometimes sensitive to extraneous electrical energy and can function prematurely. Some documented accidental initiations are as follows ... 

The Nobel family suffered many set backs in marketing nitroglycerine because it was prone to accidental initiation, and its initiation in bore holes by blackpowder was unreliable. There were many accidental explosions, one of which destroyed the Nobel factory in 1864 and killed Alfred s brother, Emil. Alfred Nobel in 1864 invented the metal blasting cap detonator which greatly improved the initiation of blackpowder. The detonator contained mercury fulminate [Hg(CNO)2] and was able... 

Recent developments of novel explosive materials have concentrated on reducing the sensitivity of the explosive materials to accidental initiation by shock, impact and thermal effects. The explosive materials, which have this reduced sensitivity, are call Insensitive Munitions, (IM). Although these explosive materials are insensitive to accidental initiation they still perform very well when suitably initiated. Examples of some explosive molecules under development are presented in Table 1.5. A summary of the significant discoveries in the history of explosives throughout the world is presented in Table 1.6. 

In this book the term sensitiveness is used to describe the response of an explosive to accidental initiation, i.e. friction, impact, etc., whereas sensitivity is used when the explosive is initiated by non-accidental methods, i.e. shock from a primary explosive. 

Solid propellant compositions which have been previously discussed all sulfer from the possibility of accidental initiation from fire, impact, electric spark, etc. Therefore, attention has turned to the development of insensitive munitions with particular emphasis on low vulnerability ammunition (LOVA). LOVA propellants contain RDX or HMX, an inert polymeric binder and a plasticizer. These composite propellants are less vulnerable to initiation than nitrocellulose-based propellants. 

The use of NG-based dynamite continued to decline during the 1990 s throughout the world. For example, by 1995 there was only one dynamite manufacturing plant left in North America, and in 2000 the dynamite production at this plant had dropped to less than half the amount produced in 1990. The reasons for the declining use of dynamite are its unpopular properties of sensitivity to accidental initiation and the headache-causing fumes. Both bulk and packaged emulsions have been slowly replacing dynamite since about 1980. 

A short-circuiting device provided on the free ends of the leg wires of electric blasting caps to protect them from accidental initiation by extraneous electricity. 

Research and development is continuing in the chemistry of explosives to produce compounds that are insensitive to accidental initiation but still highly efficient as explosives. NTO (7), ADN (8), and TNAZ (9) are good examples of explosive compounds under development and testing. 

Composite propellants. A composite propellant represents a group of propellants in which the composites, the fuels, and the oxidizers are separated materials. This type of propellant has replaced the sensitive propellants that suffer from the possibility of accidental initiation from fire, impact, electric spark, and others [4-6],... 

P. A. Davies, Accidental Initiation of Condensed Phase Explosives during Road and Rail Transport, J. Hazard. Mater., 38, 75-88 (1994). 

It is essential to minimize the quantity of material and number of personnel at any location and to utilize all appropriate protective equipment (such as barriers, safety glasses, and flak jackets) to minimize personnel injury in the event of an unexpected detonation. Cleanliness, the avoidance of gritty or other explosive substances, the wearing of appropriate (antistatic) clothing, and the electrical grounding of personnel are standard precautions taken to avoid accidental initiations. 

---