There are many types of foam fire extinguishing systems(such as using Foam Fire Extinguishing Agent): they can be divided into fixed type, semi-fixed type and mobile type according to the way of installation. According to the foam spray method, they can be divided into three types: liquid spray, liquid spray and foam spray; The bubble multiple can be divided into three types: low, medium and high. So what are their advantages and disadvantages?
Advantages and disadvantages of the liquid injection system
1. The liquid spray foam fire extinguishing system has the advantages of simple structure, convenient installation and maintenance, easy debugging and various types of foam liquids.
2. The disadvantage of liquid injection is that the foam generator and part of the pipeline are easily damaged by the combustion and explosion of the storage tank. The system is mainly suitable for the above-ground fixed vertical oil tanks, floating roof tanks and liquid storage tanks of E- and E-type liquids in oil depots.
Advantages and disadvantages of submerged injection systems
1. When the liquid is sprayed under the liquid, the nozzle is restricted by pressure. In order to ensure the quality of the fire, a high back pressure foam generator must be used.
2. The disadvantage is that the submerged spray can only be used for non-water-soluble liquid fires, otherwise it will affect the quality of the foam and affect the fire extinguishing effect. Moreover, the spout is easily corroded. The submerged spray foam system is only suitable for above-ground fixed top tanks of water-insoluble liquids of type A, B and C. It is not suitable for water-soluble liquid storage tanks of type A, B and C, nor for outer floating roof and inner floating roof storage tanks.
3. The advantage of submerged injection is that the bottom of the oil tank is generally not easily damaged, which improves the safety of the submerged foam system and also increases the effective storage capacity of the tank. In the case of fire extinguishing, the foam reaches the burning liquid level through the liquid, and does not pass the high temperature flame, thereby reducing the loss of the foam and improving the fire extinguishing effect. When the foam rises from the lower part of the oil tank to the burning liquid surface, the cold oil in the tank and the hot oil in the tank are convected, which acts as a cooling effect and is beneficial to the fire extinguishing. And you can save money by not having a dedicated foam line.
In general, a low-expansion foam fire extinguishing system should be used to extinguish flammable liquid fires. The so-called low-fold foam refers to an air foam having a foam expansion ratio of less than 20 times.
Advantages and disadvantages of low multiple foam fire extinguishing systems
(1) The system foam has a small foaming multiple and a high foam density. Therefore, the foam does not substantially rise with the hot air flow generated by the combustion, and is suitable for fighting a flammable liquid fire;
(2) The foam jet is far, and the effective height of the jet is also large, which is suitable for the mobile foam fire extinguishing system.
Low expansion foam system is not suitable for the following occasions
(1) It is generally not suitable for fighting a flammable liquid fire that is flowing;
(2) It is not suitable for fighting gas fires, liquefied gas fires with low boiling point below 0 °C and low temperature liquid fires;
(3) It is impossible to save the fire of live equipment;
(4) It is not advisable to use fire extinguishing with water gun and water spray system.