Detonators sizes

Explosives derived from Benzene—Toluene and Nitro-Benzene-Di- and Tri-nitro-Benzene-Roburite Properties and Manufacture-Bellite Properties, c.-Securite—Tonite No. 3.-Nitro-Toluene-Nitro-Naphthalene—Ammonite-Sprengel s Explosives-Picric Acid- Picrates-Picric Powders—Melinite-Abel s Mixture—Bmgere s Powders- The Fulminates-Composition, Formula, Preparation, Danger of, c.- Detonators Sizes, Composition, Manufacture—Fuses, c. 

Composition, Formula, Preparation, Danger of, c.—Detonators Sizes, Composition, Manufacture—Fuses, c. 

In the manufacture of explosives, sodium nitrate is used mainly in blasting agents. In slurries and emulsions, sodium nitrate improves stabiUty and sensitivity. It also improves the energy balance because sodium nitrate replaces water, so that more fuel can be added to the formulation. Sodium nitrate reduces crystal size of slurries, which in turn increases detonating speed. In dynamites sodium nitrate is used as an energy modifier. Typical content of sodium nitrate is 20—50 wt % in dynamites, 5—30 wt % in slurries, and 5—15 wt % in emulsions. Sodium nitrate is used also in permissible dynamites, a special type of dynamite for coal (qv) mining. 

If a large amount of a volatile flammable material is rapidly dispersed to the atmo vapor cloud forms. If this cloud is ignited before the cloud is diluted below its lower flammability limit, a UVCE occurs which can damage by overpressure or by thermal radiation. Rarely are UVCEs detonations it is believed that obstacles, turbulence, and possibly a critical cloud size are needed to transition from deflagration to detonation. 

The other detonability length scale is the detonation cell width, X (also called cell size) which is the transverse dimension of diamond shaped cells generated by the transverse wave stmctnre at a detonation front. It has a fish scale pattern (see Figure 4-4). Detonation cell widths are nsnally measured by the traces (soot) deposited on smoke foils inserted in test vessels or piping surfaces. The more reactive the gas-air mixture, the smaller is the cell size. The same is tme for chemical indnction length as a qualitative measure of detonability. The cell width, X, is a parameter that is of practical importance. The transition from dehagration to detonation, propagation, and transmission of a detonation, can to some extent be eval-... 

Tims it is possible to estimate order of magnitnde limits for detonation propagation nsing calcnlated CJ indnction zone lengths or measnred cell size data. These were limits for established detonations propagating into pipes of decreasing diameter. Variations in the detonability of different mixtnres in different pipe geometries are thns intimately linked to the initial chemical and physical properties of the mixtnre. 

However, disadvantages inclnde weight, a relatively high resistance to gas flow, and the size of the apertnres is not directly controlled. Movement of the shot or balls dnring a deflagration or detonation conld lead to failnre of the flame arrester (HSE 1980). 

Lapp, K. and Vickers, K. 1992. Detonation Flame Arresters and Larger Line Sizes. International Data Exchange Symposium on Flame Arresters and Arrestment Technology. Banff, Alberta (October 1992). 

There are no clearly discernable, broadly applicable, correlations between the 6-inch and 1 S-inch deflagration and detonation experiments. Therefore, comparisons were done on a parameter-byparameter basis. However, comparisons of data taken during experiments with the two pipe sizes reveal that enough scale-related differences exist that interpolation between the two scales for an intermediate size should be done only where conditions are very similar. Then, overpressure and specific impulse can be estimated based on L/D. 

Cell size depends strongly on the fuel and mixture composition more reactive mixtures result in smaller cell sizes. Table 3.2 shows that a stoichiometric mixture of methane and air has an exceptionally low susceptibility to detonation compared to other hydrocarbon-air mixtures. 

TABLE 3.2. Characteristic Detonation Celi Size for Some Stoichiometric Fuel-Air Mixtures... 

A deflagration-detonation transition was first observed in 1985 in a large-scale experiment with an acetylene-air mixture (Moen et al. 1985). More recent investigations (McKay et al. 1988 and Moen et al. 1989) showing that initiation of detonation in a fuel-air mixture by a burning, turbulent, gas jet is possible, provided the jet is large enough. Early indications are that the diameter of the jet must exceed five times the critical tube diameter, that is approximately 65 times the cell size. 

In a smooth tube, the onset of detonation will take place only if the internal tube diameter is larger than about one characteristic-detonation-cell size. 

If the tube is provided with internal obstructions, the open area cross-section should be greater than about three characteristic-cell sizes. Then detonation... 

As with a high explosive, a fuel-air mixture requires a minimum charge thickness to be able to sustain a detonation wave. Hence, a fully unconfined fuel-air charge should be at least 10 to 13 characteristic-cell sizes thick in order to be detonable. If the charge is bounded by a rigid plane (e.g., the earth s surface) the minimum charge thickness is equal to 5 to 6.5 characteristic-cell sizes (Lee 1983). 

The characteristic magnitudes of detonation cells for various fuel-air mixtures (Table 3.2) show that these restrictive boundary conditions for detonation play only a minor role in full-scale vapor cloud explosion incidents. Only pure methane-air may be an exception in this regard, because its characteristic cell size is so large (approximately 0.3 m) that the restrictive conditions, summarized above, may become significant. In practice, however, methane is often mixed with higher hydrocarbons which substantially augment the reactivity of the mixture and reduce its characteristic-cell size. 

The Universal Hopkinson-Cranz and Sachs Laws of Blast Scaling have both been verified by experiment. These laws state that self-similar blast (shock) waves are produced at idendcal scaled distances when two explosive charges of similar geometry and the same explosive composition, but of different size, are detonated in the same atmosphere [49]. 

Rupture disks when properly sized and located on the potentially overpressure vessel have been shown to provide the best protection for a deflagration but not a detonation [54],... 

Explosion calculations, 499-504 Estimating destruction, 501 Overpressure, 502 Pressure piling, 501, 504 Relief sizing, 505 Scaled distance, 502, 503 Schock from velocity, 503 TNT equivalent, 499-504 Explosion characteristics of dusts, 515 Explosion suppression, 518 Explosion venting, gases/vapors, 504 Bleves, 504 Explosions, 482 Blast pressure. 496 Combustion, 482 Confined, 482 Damage, 498-501 Deflagration, 482 Detonation, 483... 

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