Vapor cloud explosions with BLEVE

A vessel filled with a pressurized, superheated liquid can produce blasts upon bursting in three ways. First, the vapor that is usually present above the liquid can generate a blast, as from a gas-filled vessel. Second, the liquid will boil upon depressurization, and, if rapid boiling occurs, a blast wiU result. Third, if the fluid is combustible and the BLEVE is not fire induced, a vapor cloud explosion may occur (see Section 4.3.3.). In this subsection, only the first and second types of blast wiU be investigated. 

As described in Section 6.2.1., British Gas performed full-scale tests with LPG BLEVEs similar to those conducted by BASF. The experimenters measured very low overpressures firom the evaporating liquid, followed by a shock that was probably the so-called second shock, and by the pressure wave from the vapor cloud explosion (see Figure 6.6). The pressure wave firom the vapor cloud explosion probably resulted from experimental procedures involving ignition of the release. The liquid was below the superheat limit temperature at time of burst. 

REDIFEM—This fire model has applications including steady state releases of compressible gas/vapor, incompressible liquid and transient release from a gas vessel, Gaussian Plume models, continuous free momentum, BLEVE, and confined and unconfined vapor cloud explosions. REDIEEM is reported to have internal validation with ISO 9001 and checked against PHAST and ERED. 

Many types of outcomes are possible for a release. This includes vapor cloud explosions (VCE) (Section 3.1), flash fires (Section 3.2), physical explosions (Section 3.3), boiling liquid expanding vapor explosions (BLEVE) and fireballs (Section 3.4), confined explosions (Section 3.5), and pool fires and jet fires (Section 3.6). Figure 3.1 provides a basis for logically describing accidental explosion and fire scenarios. The output of the bottom of this diagram are various incident outcomes with particular eflfects (e.g., vapor cloud explosion resulting in a shock wave). 

Figure 1. Comparison of major accidents in Middle Eastern case (blue) with world accidents (red) in the oil and gas industry percentages of different scenarios. (LOCA Loss of containment F Fire EX Explosion BLEVE boiling liquid expanding vapor explosion IE internal explosion TOX toxic release VCE vapor cloud explosion VCF vapor cloud fire VEEB vapor escape into, and explosion in, building, B blowout).

With a BLEVE a flash vaporization occurs in the first place. It is treated below. After release a cloud is formed, which—depending on material properties—is flammable, toxic or both. In case of a flammable material explosion effects as well as the consequences of heat radiation must be envisaged. 

---