Is it true that burning oil wells and other fires can sometimes be extinguished by setting off a large explosion next to them? (The explosion consumes the surrounding oxygen, literally choking off the oil well fire.)
#120716. Asked by unclerick. (Mar 15 11 9:14 PM)
Yes, fire requires three things:|
(2) Heat source
If you take away any one of those things, you no longer have fire.
When you detonate a large enough charge near a flame, the explosion uses all of the available oxygen to burn itself out. In the end, it denies the entire area of oxygen for a moment - a moment which removes part of the triad, thus extinguishing the flame.
Of course, explosions are not very helpful in putting out something like a house fire. You might put out the fire, but you'd blow up the house. Further, in such a situation, you might extinguish the initial flame, but probably start new ones.
But in places where you have a large, point-source fire, far from any structures - like a burning oil well - explosives are a legitimate mechanism, and widely used. Once the fire has been extinguished the actual capping of the well can begin (of course, the oil is still blowing out but at least it's not burning).
The explosion does not consume the surrounding oxygen. Explosives contain their own source of oxygen. In the case of gunpowder it is potassium nitrate. When a bullet is fired the powder in the shell case does not consume the surrounding oxygen because it is obviously isolated from that oxygen.|
The method works by the explosion momentarily driving away the fuel from the point of ignition. It also drives away the surrounding oxygen, presumably by blanketing the area with its own explosion products.
"Commonly available explosives such as 80% nitroglycerin grade dynamite are still used in oil well firefighting. It is believed that M. M. Kinley invented the presently used method, which was employed by experienced firefighters in the 1920s. For the mechanism, slow-speed photography indicates that the explosion acts to temporarily drive fuel away from the point where the flame develops and deprive that immediate area of oxygen to support instant reignition. Depending on fire size and prior experience, up to 500 lb of explosive may be used."
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