【 Weak current College 】 several gas extinguishing system on

Preface

Gas fire in China began in the 1980s, 1990s, new fire and extinguishing agent in the application process has undergone many changes in fire danger, fire fighting, protection of the environment, economical and practical, and many other factors in choosing a satisfactory fire protection programmes, often very complex. This article will give some discussions only for associates.

In the nineties in library, Museum, archives and other premises completed gas fire extinguishing system, the use of halon 1301 is mostly. At that time, people think of halon 1301 is suitable for a variety of different types of fire flame inhibitor of the best. However, because of its impact on the environment, the destruction of the ozone layer of the atmosphere, causing global warming to varying degrees, in 1993, Canada launched the Montreal agreement, restrict production of substances that deplete and provided to the 2005 global prohibition of the use. Now halon substitutes are diverse, this article only discusses the CO2, FM-200, aerosol, inergen IG541 four alternative products.

A, environmental protection

Evaluation of an agent of environmental indicators in general there are three items:

1, ODP value: ozone depletion potential value;

2, the GWP values: global warming potentials;

3, ALT value: composition in the atmosphere a memory for life.

Above several gas fire extinguishing agent of environmental indicators parameters are as follows:

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From the above table comparison, 1301 the three environment characteristics index values are high, this is what it is one of the main causes of elimination. CO2 and no damage to the ozone layer FM-200, but in the atmosphere survive life is long, at the same time, large amounts of CO2 and FM-200 into the atmosphere, global warming will have a greater impact on the United States, Britain and other countries have been included in the managed use plan, are not suitable for long term alternatives to consider. But according to my existing facts, Ministry of public security still recommends the use of carbon dioxide and inert gas fire extinguishing system, you can also use containing hydrofluoric acid (HFC) fire-fighting system, so these two gases, especially CO2 extinguishing systems is still a certain amount of usage.

Aerosol is liquid or solid particles suspended in air dispersion medium a Sol. Particles of solid particles mainly metal oxides, carbonates or bicarbonates, and most of the particle size is smaller than 1 micron, accounting for more than 90%; gas mainly nitrogen, a small amount of CO2 and water vapour, aerosol extinguishing agent on the ozone layer is damaged, almost no greenhouse effect, the environmental pollution-free.

As regards inergen, greenhouse effect, ozone layer destruction not, nor will it produce a long service life of chemical substances in the atmosphere, is a real sense of "zero pollution". The main benefit from inergen is determined by three natural gas: nitrogen, argon and mixture of carbon dioxide, is taken from nature, back to nature, is an environmental factors can play full of "green" products.

Therefore, environmental impact factors, aerosol and inergen significantly better than the other two fire extinguishing agent, mankind has only one Earth, in future projects, should be considered in conjunction with the actual, as opposed to the other two fire extinguishing agent should give priority to the use of aerosol and inergen.

II. Security

CO2 fire suppression mechanism is a closed space into a large amount of CO2 gas, oxygen content in air by normal 21% lower than 15%, so as to achieve the purpose of the suspension of combustion of asphyxia. However, CO2 this suffocation have fatal hazards to human health, its minimum design fire extinguishing concentration (34%) considerably more than a person's risk of lethal concentration, great, it was often not suitable for the use of the site. If used, the gas release, personnel must be evacuated rapidly.

About FM-200 toxicity and carcinogenicity, current academic controversy and its side effects than 1301 small remains to be studied. However during the firefighting FM-200 will release a hydrofluoric acid, acid gas generation capacity is 8 ~ 1301 10 times, the actual amount of the acid generating approximately 300PPM, much larger than the short contact with hydrofluoric acid to danger 50PPM concentration of international standards in this environment, more than a minute, life-threatening. Therefore, it was often the use of the site carefully, if used, FM-200 protection zone design concentration must FM-200 fire suppression is not great and 9%.

Aerosol-fighting technology is composed of former Soviet military technology development, aerosol formulations, are relying on their own produce gas solvent to fight fires, non-toxic, firefighting air oxygen concentration will not decrease, there is no harm to people. However, for aerosol release will form a strong smoke, visibility is very low (less than 1.0 m), affecting the fire officer's escape (proved that visibility in the fire than 3.0 m, it is difficult to escape. ), Which is precisely one of the aerosol extinguishing agent's biggest flaw, since it was often not suitable for the use of the site. If used, the gas release, personnel must be evacuated rapidly.

Although inergen-fighting mechanism and CO2, is put into the pharmacy Jet closed space, reduce the oxygen concentration, asphyxia burning fight fire. However, inergen pharmacy is 52% nitrogen .40% argon and 8% of the CO2 gas composition, it mixed into the gas mixtures, makes people in anoxic atmosphere able to breathe, it actually enhances people's ability to absorb oxygen. Typically, the room air and oxygen content of 21%, CO2 content of around 1%. When injected into the inergen fire extinguishing agent, its concentration of oxygen in the room is reduced to approximately 12.5% while the CO2 concentration is increased from 2% to 5%, by the people themselves deeper and faster breathing to compensate the oxygen concentration in the environment, on a timely evacuation of people is no harm.

3. fire-extinguishing efficiency

Fire extinguishing concentration is low, less, fire extinguishant short time is a measure of fire-extinguishing systems efficiency scale. The following table:

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As the extinguishing agent fire suppression mechanism, its concentration of fire extinguishing, fire fighting time vary. CO2 and inergen is protected space filled with inert gas reduces the oxygen content up smothering and FM-200 and aerosols is terminated by chemical inhibition of combustion reaction to fire-fighting purposes. From the above table shows that CO2 and inergen minimum design fire extinguishing concentration relatively large, relative volume ratio applied too high, the use of larger, fire extinguishing is relatively slow, FM-200 and aerosol fire suppression is obvious to a rapid speed. Practice has proved that aerosol extinguishing efficiency for halon 1301 of 4 ~ 6 times, its most efficient extinguishing fire.

IV. scope of application

In General, these four fire extinguishing agent is able to respond quickly and effectively to fight a.b.c class fires not applicable fight digestion fiber, gunpowder and other strong oxidant chemical fire and lively metal, fire liable to spontaneous combustion. However, because the agent's own performance, fire-fighting mechanism, consisting of fire-extinguishing system in the range of use there is a difference on.

CO2 pressure by storage is divided into high and low pressure CO2 extinguishing system. When CO2 injection, makes ambient temperature significantly lower ("chilled" phenomenon), the moisture condensation in the air, become extremely dense mist ("dew" phenomenon), expensive electronic equipment causing serious defaced. CO2 dissolved in water and carbonated, sufficient to cause harm on magnetic medium, especially for computer labs, communication in the engine room of the integrated circuit chip, a greater impact, and the electrical equipment surface electrostatic accumulation. High pressure CO2 reservoir pressure higher, filling density 60% to 68%, design pressure for 15.0MPa, fire extinguishing agent is released easily envelope and protected from damage.

FM-200 in fire extinguishing process decomposition of hydrofluoric acid is a weak acid, but it has a specific corrosive, on specific substances can cause great damage. As with CO2 injection nozzle FM-200 in Office environment temperature, moisture condensation in the air, a thin layer of water mist, due to certain hazards.

Aerosol fire suppression systems, the current domestic engineering application of aerosol fire suppression equipment belongs to heat, heat will cause some harm; Sol to negative catalysts, asphyxia, fire-fighting; the principle behind residues, belonging to the non-fire extinguishing, suspended in the air of dust is electrically neutral, although easy to clean, but residual particulate dust containing metal oxides, carbonates, bicarbonates, in the face of weak alkaline water tested, on a specific device can cause some damage. In addition to the proliferation of aerosol colloid speed slower gas fire extinguishing agent, and thermal gel spray drop after the proliferation of trend upward, not conducive to the uniform distribution. So protective zone area and volume should be better than no pipeline halon automatic fire extinguishing system settings require more strictly, should not be used for large space.

Inergen release, spray emits gases will not produce fog or dew knot, therefore protected equipment, property and people will not have a secondary damage. However, inergen belonging to HP storage containers, pressure up to 15.0MPa, fire extinguishing agent is released easily envelope and protected from damage.

5. economic analysis

Economic analysis of the surface, both extinguishing system investment costs a one-time project, including system put into operation, equipment maintenance, such as the day-to-day Manager of normal expenses, equipment's annual periodic inspection testing costs, the cost of additional installation parts replacement for normal damage. Fire extinguishing agent, the higher the price, the more the cylinder equipment, the system of maintenance costs.

CO2 fire-extinguishing system sources plenty without synthetic, nature itself is, CO2 and populating an affordable price. But its release pipeline and nozzle shape has strict requirements, such as the design, construction, will be released during the massive ice blocking pipes or nozzles caused the accident. Application of relative volume ratio is too high, the minimum fire design concentration 34.0% usage. Low pressure CO2 liquid own storage temperature is-18 ° c, the system routine maintenance workload, maintenance costs, system management is strict, the power must be fully guaranteed, as should the use of units of management level with low pressure CO2 extinguishing system.

1301 FM-200 fire extinguishing systems and fire extinguishing system with equipment, pipeline and distribution are almost identical, is considered the closest substitutes 1301, but expensive FM-200 pharmacy, and each set FM-200 extinguishing agent for filling pressure of smaller and medium pipeline transmission distance short, therefore at current fire extinguishing agent storage pressure (the pressure for existing stockpiles and 4.2Mpa two 2.5MPA), FM-200 only applies to small systems.

Aerosol insecticides usually 6-8, costs must be replaced. Aerosol fire suppression systems, due to aerosol particles extremely fine, and has a very large surface area, the absorption of extremely strong, and therefore should not be used for pipeline transportation, only applies to small systems, such as building protection volume smaller distribution room, the transformer room, etc. But if used in a large protected area, you should use a combination of multiple sets of systems, this device consumes relatively much, the construction area is large, although still increased investment can respond quickly and effectively to put out the fire, but not reasonable.

Inergen IG-541 fire extinguishing system, are not protected area size constraints, particularly for larger fire protection engineering, by contrast, economic and reasonable. And the greater the savings investment project. High-pressure inert gases are stored, its transmission distance up to 100M. Although their overall performance is better, are excellent alternatives, but the system for fire extinguishing agents of gas ratio, storage containers, pipes, valves and nozzlesStores as well as the surrounding environment, temperature requirements, system equipment manufacturing and installation process is relatively complex. Because IG-541 is single-phase gas fire extinguishing agent, so it cannot be used for local Jet, nor to use fire extinguishers. And other gas fire extinguishing system IG-541 fire extinguishing system compared to the considerable volume of fire extinguishing agent, and therefore need more gas cylinder and thicker. In addition, it is also particularly high pipeline pressure. If the system is poorly designed, spray on, due to pipeline IG-541 gas flow reaches the Sonic and the sound barrier, the flow resistance to severely; more than Sonic arising from detonation may also make the system is compromised. For the purposes of the present situation, its comprehensive cost is the highest, more or less restricted the use of its extensive promotion.