Boiling Liquid Expanding Vapor Explosion - Case Study Example

The combination of fireball and BLEVE can be summarized in terms of three effects which include thermal radiation, pressure wave, and flying fragments. The objective of this study is to identify and raise awareness and hazard communication (HAZCOM) brought about by BLEVE as well as to recommend safety precautions in cases of BLEVE. Various case studies involving BLEVE have been included in this study to help in achieving the laid down objectives. Case Study 1 was from experiments investigating occurrences of BLEVE under different conditions whereas Case Study 2 involved actual BLEVE explosions accident.

The results have revealed that most of the BLEVE explosions happened due to leakage of Liquefied Petroleum Gas (LPG) leakage resulting from lack of awareness of potential dangers in addition to underestimation of safety precaution. Liquefied Petroleum Gas’ (LPG) demand has been on the rise, especially in the commercial and residential sectors of developed and developing countries. It is expected that the use of cleaner gaseous and liquid fuels will continue to rise in their ease in populations and demand energy is also expected to increase worldwide The Liquefied Petroleum Gas (LPG) is stored in the form of liquid under pressure, although it vaporizes into a g upon the release of the pressure.

  The Liquefied Petroleum Gas (LPG) is generally composed of butane, propane or some combination of such organic gases. The expanded uses of Liquefied Petroleum Gas (LPG) increase the potential for leaks in the Liquefied Petroleum Gas (LPG) containers as well as an increase in the potential for fire. The Liquefied Petroleum Gas (LPG) containers include portable storage tanks, tank trucks, storage tanks in commercial installations, and railroad tank cars.   Boiling Liquid Expanding Vapor Explosion (BLEVE) is one of the major risks in the storage and transportation of Liquefied Petroleum Gas (LPG) and other hazardous materials.

A BLEVE had been introduced some decades ago after various catastrophic damages academe about as a result of pressure waves originating from boiling and vaporization of Pressure Liquefied Gases (PLG) along depressurization. 

The storage vessel fragments at high speed may come out of explosion center with high velocity to bring about serious damage to industrial facilities, properties, and accidents with fatalities to operators in industries. This is an example of explosion which may take place when a vessel with liquid under pressure is ruptured. Explosions of this nature are often extremely hazardous. A BLEVE comes about when a vessel with liquid beyond its atmospheric boiling point ruptures. The Liquefied Petroleum Gas (LPG) is stored partly in liquid state, as the remainder of the container above the liquid filled with a gaseous vapor.

However, there are situations in which a BLEVE can occur with non-flammable substance which are extremely cold, such as liquid helium or liquid nitrogen or other cryogens or refrigerants. Thus, BLEVE can not often be categorized as a type of chemical explosion. On the other hand, if the Liquefied Petroleum Gas (LPG) is flammable, then it may be the case that the BLEVE takes place before the ignition of the resulting cloud of substance, resulting in the formation of a fireball and, in some cases, a fuel-car explosion, commonly referred to as a vapor cloud explosion (VCE).

A large area is usually contaminated if the materials are toxic. In most cases, BLEVE is used to refer to combination of BLEVE and fireball, that is, if the accidents involve mechanical and thermal effects simultaneously. The substances that can lead to BLEVE, including butane, propane, chorine and vinyl chloride, among others, are quite common in the industries and in various installations such as tanks and tank cars in which they can occur. Although action of fire on a container is the frequent cause of BLEVE, there are other different causes such as runaway reactions as well as collisions. 1.1 Description of BLEVE When a tank which contains liquid under pressure is exposed to heat, such as from the thermal radiation from a fire, there will be increase in pressure inside the tank.

After a while, the wall of the container will no longer be able to contain the high stress, making the walls to collapse (the steel which is often used to construct most Liquefied Petroleum Gas (LPG) containers may fail at the pressures of approximately 15 atmospheres, when the walls’ temperature reaches about 650 degrees Celsius). This often takes place in the upper section of the container in which the walls are not in contact with the liquid to bring about the cooling effect, making the temperature of the walls to increase and consequently decrease the mechanical resistance of the wall (Abbasi and Abbasi, 2007).

On the other hand, the wall in contact with the liquid will maintain a much lower temperature because it transfers its heat to the liquid. Should a safety valve open, the boiling liquid is expected to have a stronger cooling action brought about by the heat of evaporation. Upon failure brought about by the instantaneous depressurization, the liquid’s temperature becomes greater than the one corresponding to the new pressure. This liquid in this unstable condition is referred to as superheated water.

According to Chen et al. (2007), it is normal for liquids to withstand a small amount of superheating, and in some experimental conditions can be pushed far beyond the boiling point at atmospheric-pressure. However, different liquids have different limits to superheat, commonly referred to as the superheat temperature limit. When the liquid’s temperature at the moment of depressurization is higher than the superheat temperature limit, there will be an instantaneous violent flash of a fraction of superheated liquid vapor and liquid explosion, consequently releasing a biphasic liquid/vapor mixture.

This phenomenon takes place very fast (within 1 ms). The significant increase in the volume of the liquid upon its vaporization, 250 times in case of propane and 1,750 times in the case of water, together with the expansion of the already existing vapor results to a strong wave of pressure revealed by the explosion and the bursting of the container in addition to breaking of the container into many pieces.