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On BLEVE definition, the significance of superheat limit temperature (Tsl) and LNG BLEVE's
Journal of Loss Prevention in the Process Industries 40 (2016) 81
Contents lists available at ScienceDirect
Journal of Loss Prevention in the Process Industries journal homepage: www.elsevier.com/locate/jlp
Letter to the Editor
On BLEVE definition, the significance of superheat limit temperature (Tsl) and LNG BLEVE's In a recent letter in this journal (Jones, 2015), commenting a paper of two of us (Planas et al., 2015), the author has emphasized the fact that applying the term BLEVE to the explosion of a vessel containing LNG which has been heated by an external fire e and which temperature and pressure have, therefore, increased e is quite sound. This is in good agreement with the analyses of the explosions of two tank cars transporting LNG occurred in Spain (Planas et al., 2004, 2015). Jones (2015) stresses as well that there is a difference between these explosions and the one involving LPG: while this latter can occur without any external heating (as it can also happen with a steam boiler, for example), a vessel containing LNG would require a significant heating to reach a certain pressure. However, there are still some people who think that the physical explosion of a vessel containing LNG should not be considered a BLEVE. To clarify this definitely, let us remember a few definitions (among the large number that can be found in literature): e Smith, Marsh and Walls defined it for first time in 1957 (Walls, 1979) as “a failure of a major container into two or more pieces occurring at a moment when the container liquid is at a temperature above its boiling point at normal atmospheric pressure”. e Reid (1979) introduced a restrictive condition, considering that for the explosion to be a BLEVE it was necessary that the liquid reached a given minimum temperature called “superheat limit temperature”, Tsl. Experimental evidence has shown, however, that, even if this theory could be true at rather small, laboratory scale, with homogeneous heating of vessel content, at a larger scale (with non-homogeneous temperature, local heating, liquid stratification) a BLEVE can occur well below Tsl; this is why nowadays this theory is not applied anymore (Abbasi and Abbasi, 2007; Birk et al., 2007). Nevertheless, it should be taken into account that Tsl is an interesting parameter, as it has been demonstrated (Salla et al., 2006) that at this temperature the energy transferred adiabatically between the cooling liquid and the vaporizing liquid fractions is at its maximum. e CCPS (2010) has defined it as “a sudden loss of containment of a pressure-liquefied gas existing above its normal atmospheric boiling point at the moment of its failure”; this definition, restricted to pressure-liquefied gases, could not be applied to, for example, water or other liquids. We can conclude that nowadays the following definition would be a more general and correct one: “A BLEVE is the explosion of a vessel containing a liquid (or liquid plus vapor) at a temperature significantly above its boiling point at atmospheric pressure”. http://dx.doi.org/10.1016/j.jlp.2015.12.001 0950-4230/© 2015 Elsevier Ltd. All rights reserved.
According to this definition, practically all liquids and liquefied gases reaching certain storage conditions can undergo a BLEVE. Therefore, LNG must be included among these materials. Furthermore, we have still detected in the literature some confusion between the terms “BLEVE” and “fireball”, which some authors use as synonymous. This must be attributed to the fact that, when surveying the BLEVE accidents that have occurred, it is found that an important percentage of them have involved LPG. And, in this case, almost always the vessel explosion e the BLEVE e is immediately followed by a fireball, that is, the accident involves a mechanical explosion followed by a fire (Hemmatian et al., 2015). However, let us remember again that the explosion of a steam boiler e which is not followed by any fireball e is a BLEVE. So, it is clear that this word should be applied just to the explosion, and not to the subsequent (if it occurs) fireball.
References Abbasi, T., Abbasi, S.A., 2007. The boiling liquid expanding vapour explosion (BLEVE): mechanism, consequence assessment, management. J. Hazard. Mater. 141, 489e519. Birk, A.M., Davidson, C., Cunningham, M., 2007. Blast overpressures from medium scale BLEVE tests. J. Loss Prev. Process Ind. 20, 194e206. Hemmatian, B., Planas, E., Casal, J., 2015. Fire as a primary event of accident domino sequences: the case of BLEVE. Reliab. Eng. Syst. Saf. 139, 141e148. Jones, J.C., 2015. The explosion phenomenology of liquefied natural gas. J. Loss Prev. Process Ind. 38, 233. Planas-Cuchi, E., Gasulla, N., Ventosa, A., Casal, J., 2004. Explosion of a road tanker containing liquefied natural gas. J. Loss Prev. Process Ind. 17, 315e321. Planas, E., Pastor, E., Casal, J., Bonilla, J.M., 2015. Analysis of the boiling liquid expanding vapor explosion (BLEVE) of a liquefied natural gas road tanker: the Zarzalico accident. J. Loss Prev. Process Ind. 34, 127e138. Reid, R.C., 1979. Possible mechanism for pressurized-liquid tank explosions or BLEVE's. Science 203, 1263e1265. Salla, J.M., Demichela, M., Casal, J., 2006. J. Loss Prev. Process Ind. 19, 690e700. Walls, W.L., 1979. The BLEVE-part 1. Fire Command. 17, 35e37.
B. Hemmatian, E. Planas, J. Casal* Centre for Technological Risk Studies (CERTEC), Department of Chemical Engineering, Universitat Polit ecnica de Catalunya, BarcelonaTech, Diagonal 647, 08028 Barcelona, Catalonia, Spain *
Corresponding author. E-mail address: [email protected] (J. Casal). Available online 8 December 2015
Contents lists available at ScienceDirect
Journal of Loss Prevention in the Process Industries journal homepage: www.elsevier.com/locate/jlp
Letter to the Editor
On BLEVE definition, the significance of superheat limit temperature (Tsl) and LNG BLEVE's In a recent letter in this journal (Jones, 2015), commenting a paper of two of us (Planas et al., 2015), the author has emphasized the fact that applying the term BLEVE to the explosion of a vessel containing LNG which has been heated by an external fire e and which temperature and pressure have, therefore, increased e is quite sound. This is in good agreement with the analyses of the explosions of two tank cars transporting LNG occurred in Spain (Planas et al., 2004, 2015). Jones (2015) stresses as well that there is a difference between these explosions and the one involving LPG: while this latter can occur without any external heating (as it can also happen with a steam boiler, for example), a vessel containing LNG would require a significant heating to reach a certain pressure. However, there are still some people who think that the physical explosion of a vessel containing LNG should not be considered a BLEVE. To clarify this definitely, let us remember a few definitions (among the large number that can be found in literature): e Smith, Marsh and Walls defined it for first time in 1957 (Walls, 1979) as “a failure of a major container into two or more pieces occurring at a moment when the container liquid is at a temperature above its boiling point at normal atmospheric pressure”. e Reid (1979) introduced a restrictive condition, considering that for the explosion to be a BLEVE it was necessary that the liquid reached a given minimum temperature called “superheat limit temperature”, Tsl. Experimental evidence has shown, however, that, even if this theory could be true at rather small, laboratory scale, with homogeneous heating of vessel content, at a larger scale (with non-homogeneous temperature, local heating, liquid stratification) a BLEVE can occur well below Tsl; this is why nowadays this theory is not applied anymore (Abbasi and Abbasi, 2007; Birk et al., 2007). Nevertheless, it should be taken into account that Tsl is an interesting parameter, as it has been demonstrated (Salla et al., 2006) that at this temperature the energy transferred adiabatically between the cooling liquid and the vaporizing liquid fractions is at its maximum. e CCPS (2010) has defined it as “a sudden loss of containment of a pressure-liquefied gas existing above its normal atmospheric boiling point at the moment of its failure”; this definition, restricted to pressure-liquefied gases, could not be applied to, for example, water or other liquids. We can conclude that nowadays the following definition would be a more general and correct one: “A BLEVE is the explosion of a vessel containing a liquid (or liquid plus vapor) at a temperature significantly above its boiling point at atmospheric pressure”. http://dx.doi.org/10.1016/j.jlp.2015.12.001 0950-4230/© 2015 Elsevier Ltd. All rights reserved.
According to this definition, practically all liquids and liquefied gases reaching certain storage conditions can undergo a BLEVE. Therefore, LNG must be included among these materials. Furthermore, we have still detected in the literature some confusion between the terms “BLEVE” and “fireball”, which some authors use as synonymous. This must be attributed to the fact that, when surveying the BLEVE accidents that have occurred, it is found that an important percentage of them have involved LPG. And, in this case, almost always the vessel explosion e the BLEVE e is immediately followed by a fireball, that is, the accident involves a mechanical explosion followed by a fire (Hemmatian et al., 2015). However, let us remember again that the explosion of a steam boiler e which is not followed by any fireball e is a BLEVE. So, it is clear that this word should be applied just to the explosion, and not to the subsequent (if it occurs) fireball.
References Abbasi, T., Abbasi, S.A., 2007. The boiling liquid expanding vapour explosion (BLEVE): mechanism, consequence assessment, management. J. Hazard. Mater. 141, 489e519. Birk, A.M., Davidson, C., Cunningham, M., 2007. Blast overpressures from medium scale BLEVE tests. J. Loss Prev. Process Ind. 20, 194e206. Hemmatian, B., Planas, E., Casal, J., 2015. Fire as a primary event of accident domino sequences: the case of BLEVE. Reliab. Eng. Syst. Saf. 139, 141e148. Jones, J.C., 2015. The explosion phenomenology of liquefied natural gas. J. Loss Prev. Process Ind. 38, 233. Planas-Cuchi, E., Gasulla, N., Ventosa, A., Casal, J., 2004. Explosion of a road tanker containing liquefied natural gas. J. Loss Prev. Process Ind. 17, 315e321. Planas, E., Pastor, E., Casal, J., Bonilla, J.M., 2015. Analysis of the boiling liquid expanding vapor explosion (BLEVE) of a liquefied natural gas road tanker: the Zarzalico accident. J. Loss Prev. Process Ind. 34, 127e138. Reid, R.C., 1979. Possible mechanism for pressurized-liquid tank explosions or BLEVE's. Science 203, 1263e1265. Salla, J.M., Demichela, M., Casal, J., 2006. J. Loss Prev. Process Ind. 19, 690e700. Walls, W.L., 1979. The BLEVE-part 1. Fire Command. 17, 35e37.
B. Hemmatian, E. Planas, J. Casal* Centre for Technological Risk Studies (CERTEC), Department of Chemical Engineering, Universitat Polit ecnica de Catalunya, BarcelonaTech, Diagonal 647, 08028 Barcelona, Catalonia, Spain *
Corresponding author. E-mail address: [email protected] (J. Casal). Available online 8 December 2015