Explosion effects

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... 

T. N. Hak and J. R. Holden, Navy Explosives Handbook, Explosion Effects and Properties, Part 3, Properties of Explosives and Explosive Compositions, NSWC, White Oak, Md., MP-8116, Oct. 1988. 

M. M. Swisdak, Jr., ed.. Explosive Effects and Properties, TR75-116 NSWC, Oct. 1975, and Explosion Effects in Water, NSWC-TR-76-116 Feb. 1978, NSWe/NOL, White Oaks, Md. 

Energy levels contributing to explosive effects (flammable releases)... 

Toluene is a notoriously poor electrical conductor even in grounded equipment it has caused several fires and explosions from static electricity. Near normal room temperature it has a concentration that is one of the easiest to ignite and, as previously discussed, that generates maximum explosion effects when ignited (Bodurtha, 1980, p. 39). Methyl alcohol has similar characteristics, but it is less prone to ignition by static electricity because it is a good conductor. Acetone is also a good conductor, but it has an equihbrium vapor pressure near normal room temperature, well above UFL. Thus, acetone is not flammable in these circumstances. 

Table 7.10 Explosive effects of small quantities of high explosive in a 6 m x 6 m room...

Any release mode producing a combination of partial confinement, obstacles, and turbulence of unbumed gases results in very strong explosion effects. 

Van Wees, R. M. M. 1989. Explosion Hazards of Storage Vessels Estimation of Explosion Effects. TNO-Prins Maurits Laboratory Report No. PML 1989-C61. Rijswijk, The Netherlands. 

Explosion effects are commonly separated into a number of classes. The main division is between direct and indirect effects. Sometimes, direct effects ate referred to as primary effects, and indirect effects ate then subdivided into secondary and tertiary effects. 

Spreng-wirkung, /. explosive effect, explosive action, -wolke, /. cloud from an explosion, bmst smoke, -zunder, m. detonating fuse. Sprenkel, m. speckle, spot, sprenkeln, v.t. sprinkle speckle, mottle, spot. Sprenkler, m. sprinkler, sparger, sprenkllg, a. speckled, spotted. 

Photo flash bombs and cartridges are pyro technic items which are classified with bombs (Vol 2, B229) because of their explosive effect. The various devices are similar, differing principally in size and the amount of delay. When fired, each photo flash cartridge, after 1, 2, or 4 seconds, produces a flash having a peak intensity of approx 50 million cd with a total output of 5 million cd sec, whereas photoflash bombs generate above 5 x 109 cd... 

Cavitation Formation of transient voids or vacuum bubbles in a liquid stream passing over a surface is called cavitation. This is often encountered around propellers, rudders, and struts and in pumps. When these bubbles collapse on a metal surface, there is a severe impact or explosive effect that can cause considerable mechanical damage, and corrosion can be greatly accelerated because of the destruction of protective films. Redesign or a more resistant metal is generally required to avoid this problem. 

Explosion consequences in terms of overpressure and other effects may be evaluated by appropriate methods such as those described in Reference 5 and Appendix A. In evaluating the consequences of potential explosions, all these methods account for the energy of the explosion, the location of the explosion source, and attenuation of explosion effects with distance from the explosion source. From such an evaluation, maximum blast parameters can be determined at all locations of interest. Evaluation results can be graphically expressed by plotting contours of equal blast overpressure on a site plan of the facility, as shown in Figure 4.4. 

An explosion results in several structural loading effects, which can produce destmctive consequences to buildings and equipment. These consequences range from minor damage to complete collapse, depending on the structure s ability to withstand the loading effects. Table 5.1 summarizes the structural loadings that result from various explosion effects. 

Tertiary effects of explosions are those injuries or fatalities caused as people are knocked down or thrown by the blast into stationary objects. Reference 101 provides additional guidance on explosion effects on people. 

This section presents a brief description of the methods for determining the building response to explosions and how to interpret that response in terms of consequences to the building. Appendix B contains a general discussion on the principles of building design and evaluation for explosion effects. 

High humidity or damp or wet materials will weaken the explosive effect of a dust initiator, even causing a complete failure. 

Safety is known. Most DOD standard designs have been proof-tested" by exposure of a test structure to the explosive effects of a nearby detonation. The worst-case test condition is depicted in Figure 2. 

Ideally most oil or gas incidents will be controlled by the process shut down systems (ESD, depressurization, drainage, etc.) and hopeful the fire protection systems (fireproofing, water deluge, etc ), will not be required. However these primary fire defense systems may not be able to control fire incidents if previous explosions have previously occurred. Before any consideration of fire suppression efforts, explosion effects must first be analyzed to determine the extent of protection necessary. Most major fire incidents associated with hydrocarbon process incidents are preceded by explosion incident. 

The objective in calculating explosion overpressure levels is to determine if a facility has the potential to experience the hazardous effects of an explosion and, if so, to mitigate the results of these explosions. The calculations can also serve to demonstrate where mitigating measures are not needed due to the lack of a potential to produce damaging overpressures either because low explosion effects or distance from the explosion for the facility under evaluation. 

Floating exploration and production facilities are sometimes provided on jackup rigs, semi-submersible vessels or ex-crude oil shipping tankers converted to production treatment vessels. These facilities are essentially the same as fixed offshore platform or installations except they are moored in place or provided with a temporary support structure instead of provided with fixed supports to the seabed. The major process fire and explosion risks are identical to the risks produced on offshore platforms. They have one addition major facility risk, that is the maintenance of buoyancy of the installation. Should fire or explosion effects cause a loss of buoyancy (or even stability) the entire facility is at risk of submergence. Adequate compartimization and integrity assurances must be implemented in these instances. 

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