BLEVE (Boiling Liquid Expanding Vapor Explosion) Demonstration - How it ...

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Huge propane storage tank in US to meet 6 month needs

A colorado based company proposes to have a 22.7 million gallon propane insulated tank. In the report, it is stated that locals will vote about the work on the project and describes about the facility, possible effects and measures. The report has some questions and some answers. It is an interesting article. I calculated fireball radius and its duration using the equations mentioned in "Major Hazard Control: A Practical Manual" published by ILO. The fireball radius is 803 m and its duration is 124 seconds. The impact distances for thermal radiation resulting from BLEVE/VCE extend much longer. It reminds me about the incident at New Mexico in the year 1984.
The owners must have taken suitable measures as per applicable NFPA and other regulations. Risk assessment of the proposed facility with its safety features, considering the presence of other manufacturing facilities and their impact will result in a meaningful conclusion.

BLEVE Training Video - Safety Engineering Network (SAFTENG)

A video on BLEVE (boiling liquid expanding vapour explosion) is available at the link below.
BLEVE Training Video Part 1 - EXCELLENT Info - Safety Engineering Network (SAFTENG)
BLEVE Training Video Part 2 - EXCELLENT info - Safety Engineering Network (SAFTENG)

http://www.safteng.net/index.php?option=com_content&view=article&id=1038&Itemid=178 (Part 1)
http://www.safteng.net/index.php?option=com_content&view=article&id=1037%3Ableve-tests-results-1-excellent-info-&catid=52%3Aemergency-response&Itemid=178 (Part 2)
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The video explains about the phenomena of BLEVE, the fire ball radii, the safe distance for emergency responders. We will understand that the safe distance for emergency responders is FOUR times the fireball radius with minimum distance at 90 m. For a 400 lit capacity tank, the fireball radius can be 18 m. We also learn that as the capacity of the flammable storage tank increases by a factor of 10, the fire ball radius doubles. The evacuation distances can be taken as 20 times the fireball radius.

However, these distances are not exact as there are instances of explosion fragments travelling more than 20 times fireball radius. During the incident at New Mexico in 1984, a fragment weighing about 20 T travelled 1200 m.

The water required to cool the exposed hot surfaces 10 lpm/sq.m. It may be noted that inspite of all efforts, if there is whistle/jet engine sound from valves, it is indication of over pressurization inside and all emergency responders should stop their activities and move to safe distances.

Some people assume that BLEVE is possible only with flammable substances. But, as the video explains, BLEVE is possible with any substance that leads to vaporization and pressure rise during external heating/impact and the container rupture leads to BLEVE. Fireball is the result if the substance inside is flammable.

Note: Literature gives following equations:

Fireball radius, R (meters) = 29 M^1/3  where M is mass of flammable in the fireball in tonnes
Fireball duration, t (seconds) = 4.5 M^1/3

Most likely distance for 3^rd degree burns = 80 M^0.42 meters

Maximum distance for 3^rd degree burns = 130 M^0.42 meters

Most likely distance for 2^nd degree burns = 150 M^0.42 meters

Maximum distance for 2^nd degree burns = 240 M^0.42 meters

The heat radiation intensity from the fireball can cause damage to human beings and property. From the literature, it can be seen that 12.5 kw/sq.m heat intensity can be fatal, 8.5 kw/sq.m can cause 1^st degree burns whereas solar radiation gives 0.6 kw/sq.m

BLEVE

In a report (http://www.homernews.com/stories/111611/news_fdef.shtml#.TsiKjT38Kxw), it is mentioned that a fire started in a residential garage eventually led to BLEVE (boiling liquid expanding vapor explosion) and fireball involving a fuel oil tank kept inside the garage. The fireball sucked the oxygen and led to containment of fire. The fire was noticed by a neighbor who cautioned the resident of the house to escape.

Due to this, the tank failed with main tank shooting of 150 feet through a wall into the field, while the tank bottom blew through a steel door. The blown tank flew between fire fighters and nobody suffered even any minor injury.

The wind pushed the flames towards the house from garage and some front portion got burnt.

It is reported that the fire fighters heard venting sound like a jet engine and shortly afterwards, the blast took place.

The panicked owner could not tell the fire fighters about the fuel tank inside, though she told about other flammables inside. Fire fighters were unable to see the tank because of flames and heat.

There are no state fire codes to prohibit storage of fuel tanks in residential properties, though such codes exist for commercial and multi-dwelling units.

The Chief of Fire Service is not sure of proper working of vent. It is said that the fuel oil tanks are not designed to hold pressure. It appears that the fuel oil tank is having oil only to some level as per the visible line showing where it was empty.

The Chief advised to keep the oil to the full so that the heat can be absorbed and that vapor build up will be less inside the tank thus preventing pressure rise and explosion. He also feels that the tanks should be kept in open area with ventilation instead of keeping them inside.

From this incident, we can draw following lessons:

1. Flammable storage tanks should be kept outside with proper ventilation and fencing.
2. It should have proper vent relief.
3. It should have properly designed water sprinkler system.
4. It should be fenced to prevent others coming closer to it.
5. The whistle/jet engine sound from a tank exposed to fire is an indication of blast / explosion / BLEVE in a short time and all people including emergency responders should vacate the area to a safe distance.
6. No other flammable/combustible materials should be stored in the area.
7. The safe distance depends upon the maximum capacity of the storage tanks exposed to fire, the distance up to which blast fragments can travel, the distance up to which thermal radiation from a resulting fire ball can cause first degree burns, the distance up to which the over pressure can cause damage to the glass panes.
8. The name plate containing the details of the contents, capacity, design pressure, safe distance in case of fire along with emergency contact numbers should be displayed at a place easily visible and accessible, away from the storage area.
9. Periodical mock drills should be conducted to take prompt action in a real emergency.

BLEVE explanation with video

The following link gives explanation for BLEVE (Boiling Liquid Expanding Vapor Explosion). The explanatory text below states that BLEVE is possible even with nonflammable liquids which should be noted. Many experts differ with this statement and they talk firmly that BLEVE is possible only with flammable substances. Though, the phenomena is same whether it is with flammable or non-flammable substances, I do not understand why some experts in the field differ about BLEVE with non-flammables. If the substance is flammable, then BLEVE is followed with a fireball, else no fireball. Thermal radiation from fireball can trigger secondary fires (domino) if flammables are present nearby.

http://my.firefighternation.com/video/bleve-explanation