A fire extinguisher is a portable fire extinguishing tool and one of the common fire prevention facilities. The world's first fire extinguisher was born in London in 1834 and was invented by George William Manby. Fire extinguishers are stored in public places or places where fires may occur. They are divided into different types such as portable and cart types. Different types of fire extinguishers contain different ingredients and are designed for different fire causes, including foam, dry powder, Halogenated alkyl etc.
Purpose
Fire extinguishing equipment is a necessary fire-fighting equipment that is often ignored by people in ordinary times, but comes into play when it is urgently needed. Especially in today's world where there are many high-rise buildings and large amounts of wood, plastic, and fabric are used indoors for decoration, once a fire breaks out, without appropriate fire extinguishing equipment, it may cause a disaster.
The fire extinguishing equipment in ancient times was very simple, nothing more than hooks, axes, shovels, buckets and the like. The first truly dedicated fire extinguisher was invented by Manby, a British captain and Norfolk native, in 1816. It was just one or two barrels filled with more than 1 liter of water and filled with compressed air.
By the mid-19th century, French doctor Gallier invented the portable chemical fire extinguisher. Mix sodium bicarbonate and water in the barrel, and use a glass bottle to hold sulfuric acid in the mouth of the barrel. When used, the striker breaks the bottle, mixing the chemical substances, producing carbon dioxide, and forcing the water out of the barrel.
In 1905, Professor Laurent of Russia invented a foam fire extinguishing agent in St. Petersburg. He mixed aluminum sulfate and sodium bicarbonate solution and added a stabilizer. After spraying, a foam containing carbon dioxide was generated, which floated on the fire. Burning oil, paint or gasoline can effectively isolate oxygen and suffocate the flame.
In 1909, Davidson of New York obtained a patent for using carbon dioxide to press out carbon tetrachloride from a fire extinguisher. This liquid would immediately turn into a non-flammable heavier gas to suffocate the flame. Since then, dry powder fire extinguishers, liquid carbon dioxide fire extinguishers and other small fire extinguishers have appeared.
Classification
There are many types of fire extinguishers, which can be divided into: portable type and cart type according to the way they are moved; according to the power source for driving the fire extinguishing agent, they can be divided into: gas storage bottle type , pressure storage type, chemical reaction formula; according to the filled fire extinguishing agent, it can be divided into: foam, dry powder, haloalkane, carbon dioxide, water, etc.
Dry powder fire extinguisher
Principle: Dry powder fire extinguisher is filled with dry powder fire extinguishing agent. Dry powder fire extinguishing agent is a dry and easy-flowing fine powder used for fire extinguishing. It is composed of inorganic salts with fire extinguishing effects and a small amount of additives that are dried, crushed, and mixed to form a fine solid powder. Use compressed carbon dioxide to blow out dry powder (mainly containing sodium bicarbonate) to extinguish fires.
Structure: Dry powder fire extinguishers use carbon dioxide gas or nitrogen gas as power to spray dry powder in the bottle to extinguish fires. Dry powder is a dry, easy-to-flow fine solid powder, which is composed of a fire-extinguishing base material and additives such as moisture-proof agent, flow accelerator, and anti-caking agent.
Foam fire extinguisher
Principle: There are two containers in the foam fire extinguisher, which hold two liquids respectively. They are aluminum sulfate and sodium bicarbonate solutions. The two solutions do not contact each other. No chemical reaction occurs. (Do not knock over a foam fire extinguisher at ordinary times.) When a foam fire extinguisher is needed, turn the fire extinguisher upside down and the two solutions will be mixed together to produce a large amount of carbon dioxide gas:
Principle of foam fire extinguisher
< p>In addition to the two reactants, some foaming agents are also added to the fire extinguisher. When the switch is turned on, foam will spray out from the fire extinguisher and cover the burning items, isolating the burning materials from the air and lowering the temperature to extinguish the fire.Structure: The acid-base fire extinguisher consists of a cylinder body, a cylinder cover, a sulfuric acid bottle, a nozzle, etc. The cylinder is filled with sodium bicarbonate aqueous solution, and the sulfuric acid bottle is filled with concentrated sulfuric acid. There is a lead stopper at the mouth of the bottle to seal the mouth of the bottle to prevent the concentrated sulfuric acid in the bottle from absorbing water and diluting or mixing with the liquid medicine outside the bottle. The working principle of acid-base fire extinguishers is to use two agents to mix and react chemically to generate pressure to cause the agent to spray out, thereby extinguishing the fire.
Carbon dioxide fire extinguisher
Principle: The fire extinguisher bottle stores liquid carbon dioxide. When working, when the handle of the bottle valve is pressed down. The internal carbon dioxide fire extinguishing agent is sprayed from the siphon through the bottle valve to the nozzle, causing the oxygen concentration in the combustion zone to drop rapidly. When the carbon dioxide reaches a sufficient concentration, the flame will be suffocated and extinguished. At the same time, because the liquid carbon dioxide will vaporize quickly, the flame will be extinguished in a very short time. It absorbs a large amount of heat within a short period of time, thus cooling the burning material to a certain extent and also helping to extinguish the fire.
The cart-type carbon dioxide fire extinguisher is mainly composed of a bottle body, a head assembly, a nozzle assembly, a frame assembly and other parts. The fire extinguishing agent inside is liquid carbon dioxide fire extinguishing agent.
Structure: The carbon dioxide fire extinguisher barrel is made of high-quality alloy steel processed by a special process, and its weight is 40% less than that of carbon steel. It has the characteristics of easy operation, safety and reliability, easy to store, light and beautiful.
Applicable occasions: Suitable for extinguishing initial fires of flammable liquids and gases, and also for extinguishing fires in electrical equipment. It is often used in laboratories, computer rooms, power substations and distribution stations, as well as places with high maintenance requirements for precision electronic instruments, valuable equipment or items.
The fire extinguishing agent in a water fire extinguisher is water. Water has lower viscosity, higher thermal stability, higher density and higher surface tension at room temperature. It is an ancient and widely used natural fire extinguishing agent and is easy to obtain and store.
It mainly relies on cooling and suffocation to extinguish fires. Because each kilogram of water is heated from normal temperature to the boiling point and completely evaporates, it can absorb 2593.4KJ of heat. Therefore, it uses its ability to absorb sensible heat and latent heat to exert cooling and extinguishing effects, which is unmatched by other fire extinguishing agents. In addition, the water vapor formed after water is vaporized is an inert gas, and its volume will expand about 1,700 times.
When extinguishing a fire, the water vapor generated by water vaporization will occupy the space in the burning area, dilute the oxygen content around the burning material, prevent fresh air from entering the burning area, and greatly reduce the oxygen concentration in the burning area. So as to achieve the purpose of suffocating the fire. When the water is in the form of spray mist, the specific surface area of ??the formed water droplets and mist droplets will be greatly increased, which enhances the heat exchange between water and fire, thus enhancing its cooling and suffocation effects.
In addition, it can also dilute some flammable and flammable liquids that are easily soluble in water; the water mist generated by strong jets can emulsify flammable and flammable liquids and rapidly cool the liquid surface. , the production speed of flammable steam is reduced to achieve the purpose of extinguishing the fire.
Simple fire extinguisher
Simple fire extinguisher is a lightweight fire extinguisher developed in recent years. Its characteristics are that the fire extinguishing agent filling volume is less than 500 grams, the pressure is less than 0.8 MPa, and it is a small fire extinguisher that can be used once and cannot be refilled.
According to the type of fire extinguishing agent filled, simple fire extinguishers include 1211 fire extinguishers, also known as aerosol haloalkane fire extinguishers; simple dry powder fire extinguishers, also known as lightweight dry powder fire extinguishers; and simple air foam fire extinguishers. , also known as portable air foam fire extinguisher. Simple fire extinguishers are suitable for home use. Simple 1211 fire extinguishers and simple dry powder fire extinguishers can extinguish initial fires in liquefied petroleum gas stoves and angle valves on cylinders, or gas stoves, etc. They can also extinguish hot pot fires and solid objects such as waste paper baskets. A fire in which combustible materials burn. Simple air foam is suitable for initial fires caused by oil pans, kerosene stoves, oil lamps and candles, and can also be used to extinguish fires caused by solid combustibles.
Simple fire extinguishers are more suitable for permanent use at home to facilitate extinguishing sudden fires.