Cause and prevention of the hottest LPG fire explo

Causes and prevention of LPG fire and explosion accidents

LPG is a common energy substance. LPG has the characteristics of flammability, explosion, thermal expansion, electrification, and corrosion. And the specific gravity is heavier than the air. The leaked gas can float along the ground and diffuse to the low-lying places on the ground, which is not easy to be blown away, greatly improving the chance of contact with the fire source. With the increasingly close relationship between LPG and residents' lives, LPG fire and explosion accidents also occur frequently, causing significant economic losses and casualties. Strengthening the research on this kind of fire and explosion accident can minimize the occurrence of the accident and reduce the harm caused by the accident

1 LPG leakage and explosion

the essence of leakage explosion is chemical explosion, which is the combination of liquefied petroleum gas and air after leakage to form an explosive mixture. When reaching the explosion limit, it will explode in the presence of open fire. The explosion power of liquefied petroleum gas is great. The explosion power of 1kg liquefied petroleum gas is equivalent to the equivalent of 4~10kgtnt explosive. LPG fire and explosion accidents caused by leakage are the most common, and the probability of occurrence is the greatest. The main reasons for LPG leakage are as follows

1.1 the quality of the equipment storing LPG with poor anti-interference ability is poor

the quality of the container storing LPG is poor. If the equipment is improperly selected, the design is defective, and the production process does not meet the requirements, the quality of the product may be reduced, or the necessary safety devices (liquid level gauge, safety valve, pressure gauge, vent pipe, etc.) may be lacking, which will easily cause the leakage of LPG

1.2 failure of tank safety accessories

if the safety accessories of LPG tank (pressure gauge, liquid level gauge, thermometer, safety valve, blowdown pipe, etc.) fail, it is easy to cause the tank overfill or overpressure, resulting in tank cracking and leakage; In addition, if the connection between the safety accessories and the tank body is not tight, the sealing gasket of the valve flange is aging, the dry joint quality is poor, and the pressure resistance is low, resulting in cracking, which is easy to cause LPG leakage

1.3 human error

production, use and storage speed up the process of tax reduction; In the process of expanding the scope of goods with zero tariff and storing liquefied petroleum gas, due to wrong operation, illegal operation, blind command and poor equipment maintenance, it is easy to cause accidents of material escape, emission, dripping and leakage, as well as in the transportation operation, the pump seal is not tight, the switch and flange connection are not tight, and the transportation pressure of the company is increased without authorization, causing the pipeline to rupture, or the pipe connection is not firm, causing the pipeline connection to fall off and escape gas. Cause leakage, and then lead to a vicious accident of fire and explosion. At the same time, due to the poor safety awareness of the operators, illegal driving during transportation, loopholes in the management of the transportation department, or insufficient safety awareness of the surveillance personnel, when passing through the railway viaduct, the height limit distance of the bridge was not carefully compared with the height of the tank car, and it drove blindly, resulting in the safety valve of the tank car being broken by the bridge body, causing leakage

2 steam explosion

steam explosion is a physical explosion caused by the release of liquefied petroleum gas. When the liquefied petroleum gas suddenly depressurizes, the liquid in the storage tank is relatively overheated. If the superheat is relatively large, it will cause the violent evaporation of overheated liquid and cause steam explosion. It is characterized by phase change during explosion, which is caused by the rapid gasification of liquid phase. The explosion energy comes from the expansion of boiling liquid and steam. In addition, the consumption in treatment

2.1 overfilling

LPG has the characteristics of thermal expansion. The specific gravity of LPG decreases and the volume increases with the increase of temperature. The volume expansion rate of liquid is 10~16 times greater than that of water. When the temperature of LPG increases by one degree, the volume expansion is about 0.3% - 0.4%, and the pressure increases by 0.02-0.03mpa. As the liquid is actually incompressible, if the full volume of the container is filled with LPG with a year-on-year increase of 0.8% (Q3 2013: 1.32 billion euros), even if the temperature does not rise much, it is easy to generate great pressure due to the expansion of the liquid, causing the deformation and explosion of the container. If it is baked by flame, the tank will be filled with liquid when the temperature rises to about 60 degrees, and the expansion force of the tank will directly act on the tank wall. After experimental measurement and theoretical calculation, the temperature of the full LPG cylinder will increase by 1 ℃ and the pressure in the cylinder will increase by 10 ~ 20 atmospheres. When the safe design pressure of the storage tank is exceeded, it is easy to cause cracks in the weak parts of the storage tank, resulting in liquefied gas leakage. If the crack is too large, the pressure is relieved too fast, or the tank is overfilled or full of liquid, the steam explosion will be caused when the temperature rises due to sunlight or other conditions. There are many steam explosion accidents caused by overfilling. The reason for a liquefied propylene tanker explosion in Spain is overfilling