The essence of foam extinguishing system is also a kind of water fire-fighting facility. By mixing the foam proportioning device, the water and foam liquid are mixed according to the required ratio, and then the foam is generated by the foam device, and the foam is used to cover or burn the protected object to extinguish the fire. Compared with the water fire extinguishing system, it mainly consists of two parts, one is the foam proportion mixing device, and the other two is the foam generator.

泡沫灭火系统的灭火机理；

The extinguishing mechanism of foam extinguishing system.

泡沫灭火系统的灭火机理是隔氧窒息、辐射隔热和吸热冷却。泡沫灭火系统主要用于扑灭水不溶性易燃液体和一般固体火灾。灭火的原理是泡沫灭火剂水溶液通过化学和物理作用充入大量气体(CQ、空气)，然后形成无数小气泡，覆盖在燃烧物表面，使燃烧物与空气隔绝，阻挡火焰的热辐射，从而形成灭火能力。同时，泡沫在灭火过程中沉淀液体，可以冷却燃烧。加热产生的蒸汽还能降低燃烧物附近的氧气浓度，也能起到更好的灭火效果。

The extinguishing mechanism of foam extinguishing system is oxygen isolation, radiation insulation and endothermic cooling. Foam extinguishing system is mainly used to extinguish water insoluble flammable liquids and general solid fires. The principle of fire extinguishing is that the foam extinguishing agent water is filled with large quantities of gas (CQ, air) through chemical and physical action, and then forms numerous small bubbles, covering the surface of the combustion material, so that the combustion object is isolated from the air, blocking the thermal radiation of the flame, thus forming the ability of extinguishing fire. At the same time, the foam precipitates the liquid in the process of extinguishing, which can cool down and burn. The steam generated by heating can also reduce the oxygen concentration near the combustor and play a better fire extinguishing effect.

泡沫灭火系统有多种类型：固定式、半固定式和移动式根据安装；的使用情况按泡沫喷射方式可分为液体喷射、液体喷射和泡沫喷射三种类型。根据泡沫的发泡次数，可分为低、中、高三种。那么它们的优缺点是什么呢？

There are many types of foam extinguishing systems: fixed, semi fixed and mobile according to installation. The use of foam spray can be divided into three types: liquid injection, liquid injection and foam injection. According to the times of foaming, it can be divided into low, medium and high. So what are their advantages and disadvantages?

液体喷射系统的优缺点；

Advantages and disadvantages of liquid injection system;

1.液体喷射泡沫灭火系统具有结构简单、安装，维护方便、易于调试、适用于多种泡沫液体的优点。

1. the liquid spray foam extinguishing system has the advantages of simple structure, easy installation, easy maintenance, and suitable for various foam liquids.

2.注液的缺点是泡沫发生器和一些管道容易被储罐的燃烧和爆炸损坏，失去功能。该系统主要适用于油库地面固定顶立式油罐、浮顶油罐、甲、乙、丙类液体储罐等场所。

The disadvantage of the 2. injection is that the foam generator and some pipes are easily damaged by the combustion and explosion of the storage tanks and lose their functions. The system is mainly applicable to the ground fixed roof oil tank, floating roof oil tank, class A, B, C liquid storage tank and other places.

液体注射系统的优缺点：

Advantages and disadvantages of liquid injection system:

1.在液体下喷射时，喷嘴受到压力的限制。为了保证灭火质量，一定要采用高背压泡沫发生器。

1. When spraying under liquid, the nozzle is limited by pressure. In order to ensure the quality of fire suppression, high backpressure foam generator must be used.

2.缺点是液下喷射只能用于水不溶性液体火灾，否则会影响泡沫质量和灭火效果。而且喷嘴容易腐蚀。液体喷射泡沫系统仅适用于水不溶性甲、乙、丙类液体的地面固定顶储罐。不适用于水溶性甲、乙、丙类液体储罐，也不适用于外浮顶和内浮顶储罐。

The 2. drawback is that the liquid injection can only be used for water insoluble liquid fire, otherwise it will affect the quality of foam and the effect of fire extinguishing. And the nozzle is easy to corrode. The liquid ejection foam system is only applicable to ground fixed roof tanks for water insoluble class A, B and C liquids. It is not applicable to water-soluble class A, B and C liquid storage tanks, nor to external floating roof and internal floating roof storage tanks.

3.潜注的优点是油罐底部爆炸时不易损坏，从而提高了潜泡系统的安保性和油罐的储量。灭火时，泡沫到达液体下的燃烧液面，不通过高温火焰，减少泡沫的损失，提高灭火效果。当泡沫油箱从下部上升到燃烧液面时，油箱下部的冷油和上部的热油会产生对流，起到冷却作用，有助于灭火。而且可以不设置专门的泡沫管道，节省投资。

3. The advantage of submerged injection is that it is not easy to be damaged when the bottom of the oil tank explodes, which improves the security of the submerged bubble system and the storage of the oil tank. When the fire is extinguishing, the foam reaches the combustion liquid level under the liquid, and does not pass the high temperature flame, so as to reduce the loss of the foam and improve the extinguishing effect. When the foam tank rises from the bottom to the combustion level, the cold oil and the upper hot oil at the bottom of the tank will produce convection, which will play a cooling role and will help to extinguish the fire. Moreover, no special foam pipe can be set up to save investment.

一般情况下，宜采用低膨胀泡沫灭火系统扑灭易燃液体火灾。所谓低膨胀泡沫是指膨胀率小于20倍的空气泡沫。

Generally speaking, it is advisable to use low expansion foam extinguishing system to extinguish flammable liquid fires. The so-called low expansion foam refers to the expansion rate of less than 20 times the air foam.

低膨胀泡沫灭火系统的优缺点；

Advantages and disadvantages of low expansion foam fire extinguishing system;

(1)系统泡沫膨胀率小，泡沫密度高，因此泡沫基本不随燃烧产生的热气流上升，适用于扑灭易燃液体火灾；

(1) the foam expansion rate of the system is small and the density of the foam is high. Therefore, the foam does not rise with the heat flow generated by combustion, and is suitable for extinguishing the fire of flammable liquids.

(2)泡沫射流距离远，射流高度大，适用于移动式泡沫灭火系统。

(2) the distance between foam jet and jet is very high, so it is suitable for mobile foam extinguishing system.

低膨胀泡沫系统不适用于以下情况：

The low expansion foam system does not apply to the following situations:

(1)通常不适合扑灭流动的易燃液体火灾；

(1) Generally not suitable for extinguishing flowing flammable liquid fires;

(2)不应用于扑灭气体火灾、液化气

(2) It shall not be used to extinguish gas fire and liquefied gas