BLEVE

A BLEVE of a tanker

The BLEVE (abbreviation for English boiling liquid expanding vapor explosion ) is a gas explosion of an expanding boiling liquid . BLEVEs can arise in closed tank containers that contain flammable liquid or liquefied substances or substance mixtures.

In the first phase, the reaction is physically comparable to a kettle bang , only that with a BLEVE, instead of water, it is the flammable liquid substance in the tank that explodes when it escapes.

process

If a tank container is surrounded by a flammable liquid from the outside, for example in a fire (fire accident), the flames heat the container wall. The heat is transferred through the metal wall to the tank liquid, which gradually begins to boil, which increases the pressure in the tank. As long as the wall is kept at the temperature of the boiling point of the liquid by the boiling tank liquid, the metal of the wall is dimensionally stable.

If the vapor pressure of the boiling liquid in the tank reaches the triggering threshold of the pressure relief valve, which is located on the top of the tank, the gas escapes through the valve. Depending on the type of flammable gas, it either ignites itself or is ignited by the flames in the vicinity and leads to a mostly high or long flame depending on the outflow speed. Since the fire continues to supply energy in the vicinity of the tank, more liquid evaporates, so that the liquid level inside falls.

Since the heat capacity of the gas is significantly lower than that of the liquid, the tank wall above the liquid level heats up significantly above the boiling point of the liquid due to the surrounding fire, whereby the dimensional stability of the wall, depending on the heating power of the surrounding fire, decreases to a point that it corresponds to the gas pressure can no longer withstand and bursts punctually or flat, which has three consequences:

1. the broken parts of the tank act as shrapnel
2. the gas in the tank escapes completely and ignites
3. Due to the sudden drop in pressure, large parts of the remaining liquid may evaporate and also ignite

(2) and (3) lead to a massive explosion, the BLEVE.

Examples of course and effects

When a tank filled with 1,300 kg of liquid propane burst, an approx. 80 m high and approx. 50 m wide fireball was observed. The debris of the tank flew up to 500 m.

Against the background of this statement, it emerges that the most effective method of preventing a BLEVE is to fill the affected tank from the inside with a fine honeycomb-shaped aluminum net, rolled in the form of cylinders (e.g. eXess) and thus protect it before the outbreak of fire . This aluminum net distributes the heat so well that the temperature and pressure required for an explosion cannot be reached. In the case of a tank that is not protected by this aluminum net, all that remains is to cool it with water, on the one hand to minimize the temperature rise inside and to prevent the tank wall from softening. This requires very large amounts of liquid, especially with larger tanks.

According to information from the Hessian State Fire Brigade School in Kassel, the amount of water required to cool burning LPG pressurized gas bottles and autogas vehicles is 15  l / min, private liquid gas containers 180  l / min, truck semitrailers 1,200  l / min, rail tank cars 2,500 l / min.  min as well as large storage tanks or LPG tankers finally up to 150,000  l / min.

If these amounts of water are not available or cannot be applied at the required rate, BLEVE events cannot be controlled.

Accidents

Major damage events with BLEVEs occurred:

• 1948: Tank car explosion at BASF in Ludwigshafen am Rhein , Germany
• 1954: Tank farm explosion near Niederstedem
• 1966 in Feyzin , France
• 1982 in Tacoa , Venezuela . This major accident on December 19, 1982 was a hybrid between a BLEVE and a kettle crash . The starting point was a heavy oil tank in which a gas phase had evidently formed at the top. Workers opened the nozzle of a measuring line where the gas escaped and initially burned quietly. This increased the internal pressure until the upper part of the tank burst, the debris literally flying into the air. Then a large fire raged, which also hit the neighboring tank. There must have been a large amount of water in the lower part of one of the tanks. This heated up, but could not evaporate immediately due to the oil above. The evaporation started with a delay, but explosively: an even more powerful inferno than the first explosion was the result. 150 people were killed in the worst oil warehouse fire in history to date.
• 1984 Refinery disaster in San Juanico , Mexico . Here, in a warehouse with propane and butane tanks, a pipe 20 cm in diameter broke, which was not subsequently shut off by valves as intended. The resulting gas cloud exploded after 10 minutes. This external energy source (see above) led to a BLEVE in a nearby tank, which in turn triggered further BLEVEs in a row in other tanks. According to official figures, 500 people were killed, but a larger number is believed.
• On September 28, 2011, a fire broke out in a Shell petroleum refinery in Singapore . The explosions and a fireball that were then observed indicate that storage tanks that had at least one BLEVE were also affected. The fire brigade then cooled neighboring storage tanks, obviously to prevent them from BLEVES.
• On December 30, 2013, tank cars full of crude oil exploded in North Dakota as a result of a collision between moving and derailed trains.
• On March 21, 2019 in Yancheng , Jiangsu Province , China .

See also

• Flashover
• Backdraft
• Flue gas ignition

Web links

Commons : BLEVE  - collection of images, videos and audio files

• Calculation of the size of the fireball of a BLEVE depending on the mass or volume of the tank
• Boiling Liquid Expanded Vapor Explosion (BLEVE) Of Petroleum Storage And Transportation facilities (accessed February 27, 2020)
• Boiling Liquid Expanding Vapor Explosion (BLEVE) of peroxy-fuels: Experiments and Computational Fluid Dynamics (CFD) simulation (accessed February 27, 2020)
• Working healthily and safely with solvents (accessed on February 27, 2020)
• Investigations on the deterministic and probabilistic evaluation of external effects (EVA events) - effects from hazardous substances and chemical explosions (accessed on February 27, 2020)

Individual evidence

1. ↑ Hans-Joachim Gressmann, “Even» small «BLEVEs can cause problems!”, BRANDschutz 6/2001
2. ↑ Dangerous substances and goods - dangers and averting danger with liquid gas ( page no longer available , search in web archives: training and further education of the fire department Frankfurt am Main, 2003 ) (PDF; 225 kB)
3. ↑ "Dangers and Defense in the Storage and Transport of Liquid Gas", Hessische Landesfeuerwehrschule, 2006
4. ↑ NZZ on the tank disaster in Tacoa , queried on December 18, 2008
5. ↑ http://einestages.spiegel.de/static/topicalbumbackground/23944/die_katastrophe_von_san_juanico.html
6. ↑ NZZ of September 30, 2011
7. ↑ YouTube: Explosion on March 21, 2019 in the chemical park in Yancheng City in Jiangsu Province (China) (video)