Foam fire extinguishing system selection

Fire extinguishing facilities for flammable and combustible liquid storage tanks in oil depots, according to GB50074-2014, the setting of fire extinguishing facilities for flammable and combustible liquid storage tanks in oil depots: ① Soil-covered horizontal oil tanks and soil-covered vertical tanks for storing Class C and B oil products Oil tanks may not be provided with a foam fire extinguishing system, but fire extinguishing equipment shall be configured in accordance with the regulations of GB50074-2014; ≤5 seats, when the single-tank capacity of Class AB and Class B and A liquid storage tanks is ≤700m³, and the single tank capacity of Class B and C liquid storage tanks is ≤2000m³, smoke extinguishing method (that is, aerosol fire extinguishing technology) can be used; when Class A When the single tank capacity of Class B and Class B and A liquid storage tanks is ≤500m³, and the single tank capacity of Class B and Class C liquid storage tanks is ≤1000m³, superfine dry powder and other fire extinguishing methods can also be used. ③ Other flammable and combustible liquid storage tanks shall be equipped with foam fire extinguishing system.

Selection of the installation type of the foam fire extinguishing system of the storage tank: ①The above-ground fixed roof storage tank, the inner floating roof storage tank and the above-ground horizontal storage tank should be equipped with a low expansion foam fire extinguishing system or a medium The soil-covered vertical oil tanks of Class A, B, B and C A oil products shall be equipped with a low-expansion foam fire extinguishing system.

Foam liquid is divided into protein type and synthetic type. Both protein type foam liquid and synthetic foam liquid have their own advantages and disadvantages. The price of protein foam is low, and the foam has strong fire resistance, but the foam is easy to deteriorate and the storage time is short; the synthetic foam has good fluidity, strong anti-oxidation performance, and long storage time, but the foam The burning resistance is not good, and the price of foam liquid is more expensive. There are two types of protein-type foams: medium and low-expansion foams; synthetic foams have three types: high-expansion, medium-expansion, and low-expansion foams. Therefore, the fire extinguishing system also has high multiplier, medium multiplier and low multiplier foam fire extinguishing system.

High-expansion foam fire extinguishing systems are generally used to extinguish fires in confined spaces, such as fires in buildings (structures) such as cable trenches and pipe trenches.

The medium multiple foam fire extinguishing system is divided into two situations, the medium multiple foam of less than 50 times (30 to 40 times is the best) is suitable for liquid fire extinguishing of above-ground storage tanks; the medium multiple foam of more than 50 times is suitable for fighting fires , such as foam spray in buildings (structures).

Low expansion foam fire extinguishing system is suitable for open fire extinguishing. Medium expansion foam fire extinguishing system and low expansion foam fire extinguishing system have their own advantages and disadvantages due to their own characteristics: ① Low expansion foam fire extinguishing system is a commonly used foam fire extinguishing system with a wide range of applications. The foam can be sprayed from a long distance and resists wind interference It is stronger than the medium-expansion foam, and has great advantages in the liquid foam spraying of floating roof storage tanks due to its large specificity. ② The medium-expansion foam fire extinguishing system is a new type of fire extinguishing system developed by my country in the 1970s for spraying liquid on storage tanks. Due to the improvement in the performance of the protein-type medium-expansion foam liquid and the mass of medium-expansion foam is lighter than that of low-expansion foam, When spraying fire on the liquid of the storage tank, it has certain advantages over the low multiple foam fire extinguishing system. The performance is that the flow speed on the oil surface is fast, it can be directly sprayed on the oil surface, less polluted by oil, and has good fire resistance. , so the fire extinguishing speed is fast. At the same time, according to GB50151-2010, when a medium-multiplier foam fire extinguishing system is selected, the fixed-roof and internal floating-roof oil tanks of Class C, and the fixed-roof and internal floating-roof oil tanks of Class A and B with a single tank capacity of <10,000m³ should be fixed.

The setting method of the foam fire extinguishing system of the storage tank: ① The above-ground vertical storage tank of water-soluble liquid with a capacity of > 500m³ and the above-ground vertical storage tank of other Class A, B, C and A flammable and combustible liquids with a capacity of > 1000m³ shall be fixed Type foam fire extinguishing system; ②Semi-fixed foam fire extinguishing system can be used for water-soluble liquid above-ground vertical storage tanks with capacity ≤500m³ and other flammable and combustible liquid above-ground vertical storage tanks with capacity ≤1000m³;③Overground horizontal storage tanks , Soil-covered vertical oil tanks, Class B liquid vertical storage tanks and above-ground storage tanks with a capacity of ≤200m³, mobile foam fire extinguishing systems can be used.

Reasons: ①The storage tanks of oil depots are generally concentrated, and the number of fire-fighting pipelines is small. The fixed fire-extinguishing method is adopted, and the whole system can always be in a combat-ready state, with fast start-up, simple operation, and labor-saving. Since the water-soluble liquid aboveground storage tank > 500m³ and other flammable and combustible liquid aboveground vertical storage tank > 1000m³, it is difficult to extinguish fire with mobile or semi-fixed foam fire extinguishing system or cannot be extinguished in time, so it is stipulated that fixed fire extinguishing system should be used. foam fire extinguishing system. ② For the above-ground storage tank with the above-mentioned capacity, since the storage tank is small, the loss caused by fire is relatively small, and the semi-fixed foam fire extinguishing system can also be used to extinguish it, and it can also save the investment in fire protection equipment, so the semi-fixed type is allowed Foam fire suppression system. ③The mobile foam fire extinguishing system has the characteristics of flexible maneuverability, convenient maintenance and management, and no need to install foam generators and other equipment on the storage tank. It is difficult to install air foam generators for horizontal storage tanks and off-wall soil-covered vertical oil tanks. Fires in horizontal storage tanks generally only occur in small manholes, which are easy to handle, and it is better to use mobile foam fire extinguishing systems. Even if an air foam generator is installed on the tank wall of a soil-covered vertical oil tank, the tank may be burned when it catches fire; when the tank or tank chamber explodes, the collapse of the upper concrete shell may also destroy the foam generator or cause oil There was a running fire in the tank. Therefore, the soil-covered vertical oil tank can only use the mobile foam fire extinguishing system. Class C and B flammable liquid storage tanks have a very small fire probability, and the tank capacity is not large, so there is no need to invest heavily in fire fighting equipment. In case of fire, foam hooks or foam trucks can be used to extinguish the fire. Initial fires can be extinguished with fire blankets, Fire extinguishers can also save lives. The above-ground storage tank with a single tank capacity of no more than 200m3 has a low tank wall height, a small burning area, and a small amount of foam required for fire extinguishing. It can be extinguished with mobile equipment such as foam hooks.

According to GB50160-2008 (2018 edition), the fire extinguishing facilities of flammable and combustible liquid storage tanks in petrochemical enterprises should use low expansion foam fire extinguishing systems in places where flammable liquid fires may occur.

At the same time, A fixed foam fire extinguishing system should be used in the following places:

① Fixed-roof tanks of Class A, B and Class C flammable liquids with a flash point ≤ 90°C and internal floating-roof tanks with fusible material as the floating plate-a non-water-soluble flammable liquid storage tank with a single tank volume ≥ 10,000m³; b single tank volume ≥500m³ water-soluble flammable liquid storage tank.

② Floating roof tanks of Class A, B, and Class C flammable liquids with a flash point ≤ 90°C and internal floating roof tanks with non-fusible material as the floating plate-a non-water-soluble flammable liquid storage tank with a single tank volume ≥ 50000m³; b single tank Water-soluble flammable liquid storage tank with volume ≥1000m³.

③ The flammable liquid storage tanks that cannot be effectively protected by mobile fire-fighting facilities.

B The mobile foam fire extinguishing system can be used in the following places:

① Non-water-soluble flammable liquid storage tanks with pipe wall height <7m or volume ≤200m³;

② Lubricating oil storage tank;

③ Fires caused by flammable liquid flowing on the ground and oil pool fires.

Reason: The fire hazard of the lubricating oil tank is small, while the capacity of the flammable liquid storage tank is less than 200m³ and the wall height is less than 7m, the burning area is not large, and the 7m wall height can be used together with the foam hook tube and the fire ladder to fight the fire. The operation is also relatively simple, so the foam fire extinguishing system can use a mobile fire extinguishing system.