Overpressures blast damage from

In practice, overpressures in one case might very well be only one-fifth of those predicted by the method and close to the predicted value in another case. This inherent inaccuracy limits the value of this method in postaccident analysis. Even when overpressures can be accurately estimated from blast damage, released energy can only be estimated within an order of magnitude. 

The ear is a very sensitive and complex organ that responds to very small variations in pressure. It was argued in Hirsch (1968) that ear drum rupture is decisive as to ear damage from blast waves. Figure C-3 shows the percentage of eardrum ruptures as a function of side-on overpressure F,. 

Antwerp, Belgium (Ref. 16) 0 An ethylene oxide decomposition led to an overpressure and rupture of a process column. There was extensive damage to the unit and blast damage (glass breakage) as far away as 6.2 mi (10 km) from the facility. 

F. Blast effects from a nearby explosion (unconfined vapor cloud explosion, bursting vessel, etc.), such as blast overpressure, projectiles, structural damage... 

Various methods are available to limit the damage from the effects of an explosion. The best options are to provide some pre-installed or engineered features into the design of the facility or equipment that allow for the dissipation or diversion of the effects of a blast to nonconsequential areas. Wherever these mechanisms are used the overpressure levels utilized should be consistent with the risk analysis estimates of the WCCE incident. 

The extent of injury and property damage from an explosion depends on both the blast overpressure and the blast impulse at the point of interest [30]. Table 17.7 presents examples of overpressure and impulse combinations as a function of distance for an explosion having an energy equivalent of 10,000 pounds of TNT, together with the approximate limits of various types of injury and property damage. 

Equation (5) shows that for a given distance and high explosive from Table 3 we can compute the overpressure. This also holds true for the scaled distance. In summary, for the free field case we can express the damage modeling either in terms of radial distances, overpressure, blast impulse values or scaled distances. The expression for the blast impulse uses the scaled impulse [2]... 

Most of the material damage from an airburst (nuclear weapon) is caused mainly by the shock (or blast) wave which accompanies the explosion. The majority of structures will suffer some damage from air blast when the overpressure in the blast wave, i.e. the excess over atmospheric pressure (101.3 kN/m at sea level), is about 3.5 kN/m or more. The distance to which this overpressure level will extend depends on the yield of the explosion and on the height of the burst. 

Since the blast overpressure decreases rapidly as the distance from the source increases, significant offsite damage from blasts is not expected. Most studies arc directed toward on-site damage. 

FIGURE 13.2 Progression of bTBI. The sequela of events after blast overpressure exposure. Blast-induced traumatic brain injuries follow a sequence of events. Initial tissue damage from the force of blast waves lead to an evolutionary period of changes in biochemical... 

Pressure Development Overpressure in a UVCE results from turbulence that promotes a sudden release of energy. Tests in the open without obstacles or confining structures do not produce damaging overpressure. Nevertheless, combustion in a vapor cloud within a partially confined space or around turbulence-producing obstacles may generate damaging overpressure. Also, turbulence in a jet release, such as may occur with compressed natural gas discharged from a ruptured pipehne, may result in blast pressure. 

In each case, two different methods were used in arriving at estimates the HSE TNT-equivalency method and the multienergy method. The results, in the form of side-on blast peak overpressures for various distances from blast centers, are listed in Table 7.10. In addition, some peak overpressures estimated by Sadee et al. (1976/ 1977) from Flixborough-incident damage patterns are included. The photographs in Figures 7.6a and 7.6b illustrate the practical effects of such overpressures. 

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... 

The BLEVE of the spheres probably shifted a number of cylindrical vessels from their foundations. Furthermore, it probably produced damage in the built-up area. However, because destruction by intense fire in that area was complete, this cannot be confirmed. Beyond a range of 300 m, no glass damage due to blast was observed. This indicates that the side-on overpressure at that range was well below 3 kPa (0.03 bar), which is a nondimensional pressure /, of 0.04. 

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... 

People can be injured by explosions from direct blast effects (including overpressure and thermal radiation) or indirect blast effects (mostly missile damage). 

Because these loads are usually suddenly applied, and because they last from fractions of a millisecond to at most seconds, the response of or damage to loaded structures or objects is almost always dynamic. So, usually structural response or damage is dependent not only on the amplitude (peak overpressure) of the applied blast loading, the loaded area and the structural strength but also on the mass or inertia of the structure, and either the duration of the transient pressure loading or the applied specific impulse. 

Industry literature typically cites concern with open air explosions when 4,536 kgs (10,000 lbs.) or more of flammable gas is released, however, open air explosions at lower amounts of materials are not unheard of. When the release quantity is less than 4,536 kgs (10,000 lbs.), a flash fire is usually the result. The resulting fire or explosion damage can cripple a hydrocarbon processing facility. Extreme care must be taken to prevent the release of hydrocarbon from vessels resulting in vapor releases and resultant blast overpressure. Measures such as hydrotesting, weld inspections, pressure control valves, adequate pressure safety valves, etc., should all be prudently applied. 

For buildings, usually the overpressure from the blast wave is the most damaging feature of an accidental explosion in a process plant. However, in addition to the air blast elTccts, such incidents can result in fires, projectiles and ground transmitted shocks that also can be damaging to buildings and their contents. 

When a building or installation is not sited far enough away from a blast source, the building is potentially exposed to damaging overpressures. A blast resistant design is then recommended if either of the following apply ... 

The blast destroyed the cracking unit control room and the most severe damage was in the 300 ft. (90 m) by 600 ft. (180 m) unit. According to analysis of bolt stretching on the towers, the overpressure from the blast may have been as high as 10 psi. [25]... 

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