BLEVE blast by expansion‐controlled evaporation

Abstract

This report presents a new method to calculate the blast effects originating from an exploding vessel of liquefied gas. Adequate blast calculation requires full knowledge of the blast source characteristics, that is, the release and subsequent evaporation rate of the flashing liquid. Because the conditions that allow explosive evaporation are not entirely clear and the evaporation rate of a flashing liquid is unknown, safe assumptions have been adopted as the starting point in the modeling. The blast effects from a boiling liquid expanding vapor explosion (BLEVE) are numerically computed by imposing the vapor pressure of a flashing liquid as boundary condition for the gas dynamics of expansion. The numerical modeling is quantitatively explored just for liquefied propane. In addition, this paper demonstrates that often an estimate of BLEVE blast effects is possible with very simple acoustic volume source expressions.The modeling shows that the rupture of a pressure vessel containing a liquefied gas in free space develops a blast of significant strength only if the vessel nearly instantaneously disintegrates. Even if a rupture and the consequent release and evaporation of a liquefied gas extend over just a short period of time, the blast effects are minor.

“BLAST”: A compilation of codes for the numerical simulation of the gas dynamics of explosions

“…The evaporation rate is now fully determined by the rate at which the developing vapour can expand by pushing the surrounding air aside. This safe and conservative assumption of expansioncontrolled evaporation constitutes the starting point for the computation of the gas dynamics induced by the evaporation process (Van den Berg, Van der Voort, Weerheijm, & Versloot, 2004; Van den Berg, Van der Voort, Weerheijm, & Versloot, 2006). …”

“…Because of the safe and conservative starting points in the modelling, the blast charts represent an absolute maximum blast potential of superheated liquids, which has been clearly demonstrated by comparison with experimental data (Van den Berg et al, 2006).…”

Blast charts for explosive evaporation of superheated liquids

“…In the present simplified ideal gas approach however, the influence of the entrainment of the liquid phase on the expansion has been simply taken into account by including the liquid mass in the vapor mass. The inclusion of the liquid phase is the only aspect in which the present modeling is an update of the modeling presented earlier [5, 6].…”

“…In practice, an accidental disintegration of a steel vessel is mostly far from instantaneous. Simple acoustic volume source exercising has demonstrated how the blast effects strongly reduce as the vessel failure takes a small span of time [5, 6].…”

“…Therefore, a safe and conservative approach in the modeling is appropriate for the time being. Chapter 3 recapitulates and updates the numerical modeling, presented earlier by Van den Berg et al [5, 6]. Chapter 4 finally presents the blast charts compiled with the present modeling.…”