Explosions incidents

The hazard posed can be limited by maintaining a zone free of people and property around a storage area of explosive material. The minimum radius of the zone depends on the type and quantity of explosive, the extent and type of barrica ding, and the magnitude of loss that would be encountered if an explosive incident occurred. The maximum distance to which hazardous explosive effects propagate depends on the blast overpressure created, which as a first approximation is a function of the cube root of the explosive weight, W. This is termed the quantity distance and is defined as... 

The most widely deployed industrial explosion suppressant is mono-ammonium phosphate powder (MAP). This suppressant has a wide range of effectiveness. However, it can prove to be a contaminant, necessitating stringent clean-down procedures after a suppressed explosion incident. This limitation is overcome by selecting a sodium... 

The vapor cloud explosion incidents described below cover a range of factors ... 

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 long list of vapor cloud explosion incidents indicates that the presence of a quantity of fuel constitutes a potential explosion hazard. If a quantity of flammable material is released, it will mix with air, and a flammable vapor cloud may result. If... 

Furthermore, accidental vapor cloud explosions are anything but detonations of the full amount of available fuel. Therefore, practical values for TNT equivalencies of vapor cloud explosions are much lower than the theoretical upper limit. Reported values for TNT equivalency, deduced from the damage observed in many vapor cloud explosion incidents, range from a fraction of one percent up to some tens of percent (Gugan 1978 and Pritchard 1989). For most major vapor cloud explosion incidents, however, TNT equivalencies have been deduced to range from 1% to 10%, based on the heat of combustion of the full quantity of fuel released. Apparently, only a small part of the total available combustion energy is generally involved in actual explosive combustion. 

Brasie and Simpson (1968) use the Kingery and Pannill (1964) TNT blast data to represent blast parameter distributions, and the US Atomic Energy Commission s recommendations (Glasstone 1962) for the attendant structural damage. Brasie and Simpson (1968) base their recommendation for the TNT equivalency of vapor clouds on the damage observed in three chemical-plant explosion incidents. Analyzing the... 

In addition, Eichler and Napadensky derived TNT equivalencies from the damage observed in some major vapor cloud explosion incidents of the 1970s ... 

Although it recognized that much higher values have been occasionally observed in vapor cloud explosion incidents, the U.K. Health Safety Executive (HSE) states that surveys by Brasie and Simpson (1968), Davenport (1977, 1983), and Kletz (1977) show that most major vapor cloud explosions have developed between 1% and 3% of available energy. It therefore recommends that a value of 3% of TNT equivalency be used for predictive purposes, calculated from the theoretical combustion energy present in the cloud. 

As a tool for estimating the loss of property potential of vapor cloud explosion incidents at chemical plants or refineries, the possibility of two credible incidents is considered. 

TNT equivalencies given by the sources identified below are based upon averages deduced from damage observed in a limited number of major vapor cloud explosion incidents ... 

In the first approach, a vapor cloud s potential explosive power is proportionally related to the total quantity of fuel present in the cloud, whether or not it is within flammable limits. This approach is the basis of conventional TNT-equivalency methods, in which the explosive power of a vapor cloud is expressed as an energetically equivalent charge of TNT located in the cloud s center. The value of the proportionality factor, that is, TNT equivalency, is deduced from damage patterns observed in a large number of vapor cloud explosion incidents. Consequently, vapor cloud explosion-blast hazard assessment on the basis of TNT equivalency may have limited utility. 

TNT-equi valency methods express explosive potential of a vapor cloud in terms of a charge of TNT. TNT-blast characteristics are well known fiom empirical data both in the form of blast parameters (side-on peak overpressure and positive-phase duration) and of corresponding damage potential. Because the value of TNT-equiva-lency used for blast modeling is directly related to damage patterns observed in major vapor cloud explosion incidents, the TNT-blast model is attractive if overall damage potential of a vapor cloud is the only concern. 

Conventional TNT-equivalency methods state a proportional relationship between the total quantity of flammable material released or present in the cloud (whether or not mixed within flammability limits) and an equivalent weight of TNT expressing the cloud s explosive power. The value of the proportionality factor—called TNT equivalency, yield factor, or efficiency factor—is directly deduced from damage patterns observed in a large number of major vapor cloud explosion incidents. Over the years, many authorities and companies have developed their own practices for estimating the quantity of flammable material in a cloud, as well as for prescribing values for equivalency, or yield factor. Hence, a survey of the literature reveals a variety of methods. 

Blast overpressures calculated by the TNT-equivalency method are in reasonable agreement with the overpressures deduced from observed damage (Sadee et al. 1976/1977). This is to be expected, because the Flixborough incident is one of the major vapor cloud explosion incidents on which the TNT-equivalency value of... 

Explosive Incidents. Incidents which have involved mixts with perchloric ac which are normally safe, but which have expld as a result of unusual circumstances or mishandling ... 

See entries dust explosion incidents, refractory powders See other metal non-metallides... 

The compound is explosive when pure, and sensitive to impact or heat. It is stabilised for commerce by the presence of a major excess of mercuiy(II) cyanide [1]. Several explosive incidents have been described [2], most involving friction [3],... 

See entry dust explosion incidents (reference 22) See other ORGANIC BASES... 

See entry thermochemistry and eyothermic decomposition (reference 2) See other dust explosion incidents... 

See Other DUST EXPLOSION INCIDENTS, AUTOIGNITION INCIDENTS... 

Zirconium Fire and Explosion Incidents, TID-5365, Washington, USAEC, 1956 Calcium disilicide exploded when milled in the solvent. 

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