Types of aqueous extinguishing agents, performance characteristics and applications

1. Additives in water to change the nature of water-based fire extinguishing agents

(1) strengthen water

Add alkali metal salts or organometallic salts in water to improve the anti-combustion performance of materials in the fight against Class A fires, which can be used directly in the fire truck.

(2) Emulsified water

Add emulsifier, mixed with water to mist spray, because the emulsifier contains water-repellent groups, can put out oil fires with high flash points, can also be used for oil spill cleanup.

(3) wetting water

Add a small amount of viscosity enhancer to improve the wetting ability of water. For some poor wetting ability of water materials, such as plastic, synthetic fibers, rubber, etc., can reduce the surface tension of water, increase the wetting ability of water, improve the ability of water to put out fires.

(4) anti-freezing water

The high freezing temperature of the water, cooling density change greatly, the use of water at low temperatures is more difficult. The use of dilute solution dependent on the number of anti-freeze agents added to the water so that the freezing point of water to reduce, improve the effective use of water in cold areas. Commonly used antifreeze agent has two types, one is inorganic salts (such as calcium chloride, potassium carbonate, etc.), the other is polyol (such as ethylene glycol, glycerol, etc.).

(5) viscous water

Add thickener to water, improve the viscosity of water, increase the adhesion of water on the surface of the burning material, especially on the vertical surface, to prevent the loss of fire fighting water. Especially suitable for fire fighting water tankers in the building fire, to achieve the purpose of water-saving, water conservation, to avoid “extinguishing the fire, caused by water damage.

(6) Flow improvement water

Add drag-reducing agent, reduce the resistance of water in the process of water belt delivery, so that the water in the longer water belt flow, pressure loss is reduced, so you can correspondingly improve the end of the water belt or nozzle pressure, improve the distance and range of water delivery. Commonly used drag reducing agents are polyacrylamide, polyethylene oxide, Gal resin, etc., its molecular weight in the 10 ° level, add flower degree in 0.01% ~ 5%. For example, the Shanghai Institute of Machinery developed PWC and PW-30 type polymer drag reducing agent, successfully applied in urban firefighting work. Using the concentration of (100 ~ 150) x 10-6 PWC and W30 dilute solution, in Shanghai, Lanzhou, and other cities for on-site firefighting experiments, fire extinguishing effect is very good, adding the reducing agent, the flow increased by 57.1%, the range increased by 107%.

(7) water colloid extinguishing agent

Hydrocolloid extinguishing agents can be divided into inorganic hydrogel and polymer hydrocolloid extinguishing agents. Inorganic hydrogel development is more, is inorganic silica gel material for inorganic hydrogel and high score into flowering agent and water mixed reaction to generate silica gel, any silica gel, silicon, and oxygen shape for the base material, and the promoter, blocker-like space structure, water-filled in between the silicon and oxygen skeleton, due to the water and silicon and oxygen skeleton has a strong intermolecular force and hydrogen bonding so that the easy flow of water fixed inside the silica gel. After the silica gel encounters high temperature, the water in it quickly vaporizes, which can quickly reduce the surface temperature of the combustion body, the residual solids formed by the inclusions, preventing the combustion body from further contact with oxygen oxidation exothermic; and because the silica gel makes the easy flow of water fixed, reducing the mobility of water, extending the residence time of water in the combustion system, effectively play a cooling effect of water, resulting in the surface and internal temperature of the combustion body significantly decreased.

With the development of polymer science, the use of polymer materials instead of inorganic fillers, this fire extinguishing agent is called polymer water colloid fire extinguishing agent, can also be called viscous water. Due to its small addition, it can be used not only for building fires, and now has replaced inorganic hydrogel extinguishing agents for forest and mine fires.

(8) Wet chemical fire extinguishing agent

A wet chemical extinguishing agent is a new type of water extinguishing agent dedicated to fighting cooking oil fires or fat fires. In the past, the cooking oil fire was a class B fire, generally, with foam, dry powder, or CO2 extinguishing agent to put out, because the fat burning high temperature, causing fat gel, not as easy as fighting gasoline fire, therefore, the effect is not satisfactory. At present, Japan, the United States, Australia, and other countries use a new wet chemical fire extinguishing agent to put out the fire, when it comes to contact with fat fire, it will make fat saponification, the formation of a cooling effect of soap film, fire extinguishing effect is good. Usually filled in portable fire extinguishers or simple fire extinguishers, some countries also call this kind of extinguishing agent frying pan extinguishing agent.

(9) cold fire extinguishing agent

The cold fire extinguishing agent is a product of the U.S. Global Cold Flame Company, which began to enter our market after 1995. It can extinguish A, B, D class fire. Its fire extinguishing principle in addition to the general fire extinguishing agent cooling, asphyxiation, isolation, chemical inhibition, but also has a photochemical effect, from a macroscopic point of view, cold fire extinguishing agent seems to greatly increase the heat capacity of water so that the water’s ability to absorb heat greatly increased, thus showing the effect of cold fire extinguishing agent rapid-fire extinguishing and cooling. The fire extinguishing agent can be used both in the fire truck, but also in the fixed fire extinguishing facilities.

(10) SD series water-based extinguishing agent S-10-AB?

SD series water-based fire extinguishing agent is a product developed by the Tianjin Fire Science Research Institute in the 1990s, its main mechanism is to add viscosity enhancers and chemical additives to produce non-flammable gas in water, thus improving the wettability of water, flame retardancy, heat absorption, and cooling and foaming asphyxiation. According to the different combustible combustion properties, the choice of different viscosity enhancers and the addition of suitable emulsifier, SD series of high-efficiency water-based extinguishing agent can be used for A, B class fires and polar solvent fire fighting. At present, SD series water-based extinguishing agent has been used to fill various specifications of portable fire extinguishers and simple fire extinguishers can replace halogenated fire extinguishers in non-essential places, and can fully replace chemical foam extinguishing agent.

(11) water-based fire extinguishing agent in the preservative and corrosion inhibitor

In order to ensure the storage stability of water-based fire extinguishing agents and reduce the corrosion of the container, the need to add corrosion inhibitors and anti-corrosion agents in the water.

Water-based fire extinguishing agent in long-term storage, the water will breed a variety of bacteria, mold, fire extinguishing agent to produce precipitation and odor, reducing fire performance. Therefore, the need to add a preservative in the water. Commonly used preservatives are benzoic acid (sodium), p-chlorine-m-cresol sodium, potassium sorbate, benzylic acid, aniline salicylate, ammonium cationic viscosity enhancer Chapter 3 water and water-based fire extinguishing agents 65

etc. The amount added is generally 0.01% to 0.1%.

Water-based fire extinguishing agents on the corrosion of metal containers can not be ignored. There are two ways to prevent corrosion: – one is to coat the inner wall of the metal container with a protective material layer (such as plastic), the other is to add a corrosion inhibitor in the water to inhibit corrosion.

(12) Plant-based compound fire retardant agent

Plant-based composite flame retardant fire extinguishing agent, mainly using water, plants, and plants grass ash composition. The plants required to be selected as raw materials are artemisia, elm, mugwort, cycads, saponins, and plant roots containing gum. Quality requirements: must contain at least one kind of flame retardant substances (such as phosphate, potassium carbonate), active substances (such as fatty acids, polysaccharides), foaming substances (such as saponins, proteins), conjunctive substances (such as gum, cellulose) and other seasonal plants that meet the requirements of bioactive preparation of the product.

2. Change the physical properties of water to improve the water extinguishing effect of water-based fire extinguishing agents

By changing the physical properties of water to improve the water fire extinguishing effect of water-based fire extinguishing agents is a hot spot for fire extinguishing agent research in various countries, fine water mist, ultra-fine water mist fire extinguishing technology is a typical example. Ultra-fine water fog fire extinguishing mechanism is the use of special treatment of the nozzle, through the water and different atomization medium to produce water particles, water fog particle size is generally in the range of 40μm to 200μm, the specific surface area of 1700 times larger than the general water droplets, in the fire can be completely evaporated, high efficiency of heat absorption, cooling effect, can be shot into the fire area deep, fire extinguishing effect greatly improved.