BLEVEBoiling Liquid Expanding Vapour Explosion

Michael Plagge

Physics DepartmentCompact Muon Solenoid Experiment

European Organization for Nuclear Research (CERN)

Institute of Process Equipment and Environmental EngineeringDepartment of Process Design and SafetyOtto-von-Guericke-University Magdeburg

October 21, 2011

Definition [1]

A boiling liquid expanding vapour explosion, called BLEVE, is caused by afailure of a pressure vessel containing a flammable pressurized liquid due toexposure to fire or any kind of external heating.

Example:▸ Tank with liquid propane▸ Pressure is suddenly released due to a valve failure or leak caused by

aged material etc.▸ Fraction of the propane will vaporize immediately▸ Vapourization process is fed by the heat of the liquid → cooling of the

liquid to atmosphere boiling point▸ Ignition of the vapour, gas and liquid leads to a fireball

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[1] Drysdale, D., An Introduction to Fire Dynamics, 3rd Ed., John Wiley & Sons, 2011.

Example - Mexico City 1984 [2]

”About 5.35 a.m on the morning of 19 November 1984 a major fire and aseries of explosions occured at the PEMEX LPG terminal at San JuanIxhuatepec (San Juanico), Mexico City. Some 500 hundred people werekilled and the terminal was destroyed.”

Sequence of events:▸ Rupture of an eight inch pressure pipeline▸ Safety systems failed, LPG release continued▸ Accumulation of a LPG vapour cloud, area about 200x150 m, 2 m height▸ Ignition of the vapour resulting in two main and a lot of minor BLEVEs,

explosions and detonations as well as several severe fires

Two major BLEVEs were registered with a value of over five on the Richterscale for earth quakes. Fragments and parts traveled up to 1200 m

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[2] Lees, F. P., Loss Prevention in the Process Industries, Volume 3, 2nd Ed., Butterworth-Heinemann, 1996.

Example - Mexico City 1984 [2]Before the incident

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[2] Lees, F. P., Loss Prevention in the Process Industries, Volume 3, 2nd Ed., Butterworth-Heinemann, 1996.

Example - Mexico City 1984 [2]After the incident

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[2] Lees, F. P., Loss Prevention in the Process Industries, Volume 3, 2nd Ed., Butterworth-Heinemann, 1996.

Example - Mexico City 1984 [2]Schematic view of damage and accelerated fragments or missiles

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[2] Lees, F. P., Loss Prevention in the Process Industries, Volume 3, 2nd Ed., Butterworth-Heinemann, 1996.

Fireball - Caculation example [3,4]Traffic accident caused BLEVE by a fuelling vehicle

A truck filled with about 20 m3 of liquid propane has an accident andundergoes external heating due to a fire. The full amount of propane shall beconsumed in an occuring BLEVE.

x in m q̇ in kW/m2 Effects [5]100 89.1 3rd degree burns, 50% lethality200 32.91 2nd degree burns500 6.0 some pain

1000 1.53 below pain thresholdx = ground distance, q̇ = heat intensity

See References and MS Excel file for equations and assumptions.

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[3] Lees, F. P., Loss Prevention in the Process Industries, Volume 2, 2nd Ed., pp. 16/182, Butterworth-Heinemann, 1996.[4] Marx, M., Advanced explosion protection, Lecture, Otto-von-Guericke-University Magdeburg, 2009.[5] Hyms, I., The effects on people and structures of explosion, blast, thermal radiation and toxicity, In Pitts, J.I. 1984, op. cit., see [1].

Flash evapouration / Flashing

A flash vapourization due to a damage or rupture of a vessel could beassumed as a point source. The concentration C in distance r and time tafter flashing can be calculated by [6]:

C(r , t) =a3

6(kt)1.5π0.5 e−r24kt C0

C0 - initial concentration after flashingk - turbulent exchange coefficienta - diameter of the vapour cloud

Example:Rupture of a spherical vessel containing liquid propane (about 523 m3) wouldcreate a vapour cloud with a radius of 53 m. The concentration in 100 m fromthe vessel after 60 s will be around 104.9 mg/m3 (equal to 0.18 ppm). Valuesare corrected [7].

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[6] Hauptmanns, U., Technical Risks II: Incident effects, Lecture, Otto-von-Guericke-University Magdeburg, 2009.[7] http://gestis-en.itrust.de/nxt/gateway.dll/gestis en/p/010020.xml?f=templates&fn=default.htm

Flash evapouration / FlashingCERN CMS Nitrogen vessel at point 5

0,00  

0,20  

0,40  

0,60  

0,80  

1,00  

1,20  

1,40  

1,60  

0   50   100   150   200  

Concen

tra)

on  in  kg/m3  

Time  t  in  s  

Concentra)on  (10  m,  t)  

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Calculation of a dense gas with the point source model briefly described above. Do not use this for real applications, see Lees, F. P., LossPrevention in the Process Industries, Volume 1, 2nd Ed., pp. 15/162, Butterworth-Heinemann, 1996, for dense gas modeling.

Flash evapouration / FlashingCERN CMS Nitrogen vessel at point 5

0,00  0,02  0,04  0,06  0,08  0,10  0,12  0,14  0,16  0,18  

0   50   100   150   200  

Concen

tra)

on  in  kg/m3  

Time  t  in  s  

Concentra)on  (20  m,  t)  

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Calculation of a dense gas with the point source model briefly described above. Do not use this for real applications, see Lees, F. P., LossPrevention in the Process Industries, Volume 1, 2nd Ed., pp. 15/162, Butterworth-Heinemann, 1996, for dense gas modeling.

Flash evapouration / FlashingCERN CMS Nitrogen vessel at point 5

0,00  

0,01  

0,02  

0,03  

0,04  

0,05  

0,06  

0   50   100   150   200  

Concen

tra)

on  in  kg/m3  

Time  t  in  s  

Concentra)on  (30  m,  t)  

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Calculation of a dense gas with the point source model briefly described above. Do not use this for real applications, see Lees, F. P., LossPrevention in the Process Industries, Volume 1, 2nd Ed., pp. 15/162, Butterworth-Heinemann, 1996, for dense gas modeling.