Heptafluoropropane relies on product characteristics and has occupied the main position of gas fire extinguishing for a long time. High efficiency, cleanness, no pollution and sufficient supply are the major advantages of heptafluoropropane, while carbon dioxide also occupies an irreplaceable position in gas fire extinguishing. What is the difference between the two? This article will take you to popularize science.
First, introduce the carbon dioxide fire extinguishing system
Fire extinguishing principle of carbon dioxide fire extinguishing system: when the gas carbon dioxide is liquefied under high pressure or low temperature, the volume of the gas expands sharply and absorbs a lot of heat at the same time, which can reduce the temperature of the fire extinguishing site or the protected area, and dilute the oxygen content of the protected space through the high concentration of CO2 gas, so as to achieve the effect of suffocation and fire extinguishing.
Advantages of carbon dioxide extinguishing agent and extinguishing system: Because carbon dioxide is easy to be liquefied, it is easy to fill and store, which is less difficult in manufacturing technology, and its price is relatively cheap. When extinguishing, it does not pollute the fire environment, and does not cause corrosion and destruction to the protected objects in the reserve. It can not only extinguish class A, B, C fires, but also extinguish solid deep-seated fires at high concentrations, Therefore, it shows better function in places where water and foam extinguishing agent cannot be protected.
Of course, the carbon dioxide fire extinguishing system also has its inevitable shortcomings: because the carbon dioxide fire extinguishing agent needs 34% - 75% of the fire extinguishing concentration to fight a fire, the carbon dioxide fire extinguishing system must make it liquefied for storage and transportation. High pressure system for high-pressure liquefaction storage and low-pressure system for low-temperature storage are usually used. High pressure storage, in practical applications, requires a large number of cylinder groups, a large area of storage room, and high pressure, which requires strict temperature requirements for the storage environment. In summer, it is particularly necessary to pay attention to the risk of cylinder explosion caused by the rise of storage temperature. Therefore, in the design, it is generally required that the storage room should not be directly exposed to sunlight. In addition, the carbon dioxide high-pressure fire extinguishing system also needs high-pressure nitrogen drive to realize the automatic startup of the system. There are many accessories of the system, which increases the investment cost on the one hand, and on the other hand, due to the many accessories, the probability of system failure increases, which brings difficulties to maintenance. At the same time, due to high-pressure storage, the annual leakage rate reaches about 5%, which is also very difficult to make up pressure every year. CO2 is easy to form "dry ice" in the process of liquid gas, and dry ice can be directly sublimated into gas. In the process of sublimation, the volume of the gas expands thousands of times violently, causing serious damage to the transmission pipeline, making the pipeline vulnerable to cold brittleness and fracture, causing injury and damage to personnel and protection areas. In addition, the gas can also generate static electricity in the expansion process, which may cause fire; In addition, the design concentration of CO2 is too high, which may lead to the risk of suffocation of personnel who fail to evacuate safely from the protection area. Therefore, the carbon dioxide fire extinguishing system cannot be used in places where people often stay or work. In terms of spraying time, the spraying time of carbon dioxide fire extinguishing system is long, up to 60 seconds.
The birth of heptafluoropropane was an ideal substitute for halon fire extinguishers at that time. It did not damage the ozone layer of the atmosphere. The potential value of ozone depletion ODP was zero, but it had a great greenhouse effect. At the same time, because of its strong fire extinguishing efficiency and extremely mature market, it was impossible to find a good substitute until the emergence of perfluoroethylene, but perfluoroethylene was not mature in the market, Heptafluoropropane cannot be completely replaced.
Fire extinguishing principle of heptafluoropropane: the mechanism of heptafluoropropane fire extinguishing system is very similar to that of halogenated alkyl series fire extinguishing agents, which belongs to the category of chemical fire extinguishing. Fluorine containing radicals are generated through the thermal decomposition of fire extinguishing agents, and act with the gas generated by H, oh-, O2 active radicals that produce branched chain reaction in the combustion reaction process, so as to suppress the chemical reaction in the combustion process to implement fire extinguishing
Advantages of heptafluoropropane fire extinguishing system: heptafluoropropane fire extinguishing system has strong and fast fire extinguishing efficiency, fast fire extinguishing speed, good effect, low fire extinguishing concentration, which is basically close to the fire extinguishing concentration of the predecessor Halon 1301 fire extinguishing system, and the spraying time is fast. After spraying in 8 to 10 seconds, it can quickly extinguish the fire.
