Understanding few Types of Explosion occuring in Oilfield

An explosion is a type of fire but one which combusts with such a rapid force that it causes an effect known as overpressure (explosion). Under certain conditions,
the speed of the front of the flame may move to a supersonic level, resulting in a significantly more powerful explosion.

There are three types of explosions that are associated with the oil and gas industry. These are:

1. Boiling Liquid Expanding Vapour Explosion (BLEVE)
2. Confined Vapour Cloud Explosion (CVCE)
3. Unconfined Vapour Cloud Explosion (UVCE)

We will now look at a scenario whereby a Liquefied Petroleum Gas (LPG) storage vessel is exposed to an external source of heat – possibly a fire. The LPG is kept in a liquid state inside the vessel because it is held at a temperature below its boiling point, which means it takes up substantially less space than in its gaseous state. Anything which changes that state from a liquid to a gas, such as the external source of heat (fire), will increase the pressure inside the storage vessel to a potentially unsustainable level.

At first, the vapor will be vented out via the pressure relief valve on the top of the vessel. However, the rate of increase in pressure under these circumstances is likely to be unsustainable and the vessel is likely to eventually fail, with a consequential loss of containment. The resulting instantaneous release of LPG vapor will likely make contact with a source of ignition, resulting in a Boiling Liquid Expanding Vapour Explosion (BLEVE).

Should a situation occur whereby a source of heat (fire or otherwise) begins to radiate itself onto an LPG storage vessel, the following action should be taken.
Apart from removing or extinguishing the source of heat, the storage vessel, and any other storage vessels nearby, should be deluged with copious amounts of water to keep the metal cool.

A confined vapour cloud explosion is an explosion following a leak of vapour which occurs in a confined space, such as a building or a tank.

An unconfined vapour cloud explosion is an explosion following a leak of vapour which occurs in an unconfined space, outdoors.