
Foam fire extinguishing system is produced with the development of the petroleum industry. As early as the 1930s, some developed countries began to apply foam fire extinguishing systems. After entering the 1980s, with the promulgation of corresponding technical standards, foam fire extinguishing systems have been widely used. The main places of application are production areas of petrochemical enterprises, oil depots, underground engineering, garages, warehouses, coal mines, large hangars, ships, etc.
General provisions for foam fluids and system components
Foam fire pumps, foam liquid pumps, foam proportional mixers (device), pressure vessels (pressure storage tanks containing 100% aqueous film-forming foam liquid, power cylinders, driving gas cylinders), foam For generating devices (foam generators, foam guns, foam cannons, foam nozzles, etc.), fire detection and start-up control devices, valves, pipelines, etc., it is the most basic prerequisite to select products that meet the current relevant standards.

The main components of the system should be painted according to the following regulations:
- Foam fire pumps, foam liquid pumps, foam liquid storage tanks, foam generators, foam liquid pipes, foam mixture pipes, foam pipes, pipe filters, etc. should be painted red;
- Water supply pipes should be painted green;
- When there are many pipelines and there is a contradiction between the coloring of the foam system pipeline and the processing pipeline, the corresponding color band or color ring can be painted;
- Concealed engineering pipelines do not need to be painted.
Selection and storage of foam solution ,how to choose?
① The selection of foam liquid for non-water-soluble Class A, B, and C liquid storage tanks for fixed low-expansion foam fire extinguishing systems shall meet the following requirements:
- 3% fluoro protein or aqueous film-forming foam should be used;
- For environmentally sensitive areas near the red line of ecological protection, drinking water sources, permanent basic farmland, etc., 3% fluoro protein foam liquid that does not contain strong acid and alkali salts should be used;
- When choosing an aqueous film-forming foam solution, the anti-burning level of the foam solution should not be lower than grade C.
② The selection of foam-water spray system, foam gun system, and foam gun system foam liquid for protection of non-water-soluble liquids shall meet the following requirements: - When using an air-breathing foam-generating device, 3% fluoro protein and aqueous film-forming foam liquid can be used;
- When using a non-breathing spray device, a 3% aqueous film-forming foam solution should be used.
③ For water-soluble A, B, C liquids and other A, B, C liquids that have destructive effects on ordinary foams, anti-solubility water film-forming, anti-solubility fluoro protein or low-viscosity anti-solubility fluoro protein foams must be selected.
④ When water-soluble liquids and non-water-soluble liquids are stored in the protected place at the same time, the selection of foam liquid should meet the following requirements: - When the single-tank capacity of the storage tanks in the storage tank area is less than or equal to 10,000m³, anti-solubility water film-forming, anti-solubility fluoro protein or low-viscosity anti-solubility fluoro protein foam liquid can be selected; when there is a single tank capacity greater than For storage tanks of 10,000m³, corresponding foam solutions should be selected for water-soluble liquid storage tanks and non-water-soluble liquid storage tanks according to the above regulations.
- When the foam-water spray system is used in the protection place, the anti-solvent water film-forming and anti-solvent fluoro protein foam liquid should be selected.
⑤Fixed medium-expansion or high-expansion foam fire extinguishing system should use 3% foam liquid.
⑥ When seawater is used as the system water source, the foam solution suitable for seawater must be selected.

How to store it?
The foam liquid should be stored in a dry and ventilated room or an open shed; the ambient temperature of the storage should meet the requirements for the use temperature of the foam liquid.
Foam Extinguishing System Components
It is mainly composed of a fire-fighting water pump, fire-fighting water pump, foam fire extinguishing agent storage device, foam proportion mixing device, foam generating device and pipelines, etc.
It is a system that mixes the foam fire extinguishing agent and water in proportion to form a foam mixture through a foam proportional mixer, and then forms air foam through a foam generating device, and then releases it to the fire object to extinguish the fire.
According to the different multiples of foam generation, it can be divided into three systems: high, medium, and low multiples.
The main fire extinguishing mechanism of the high-expansion foam system is to close the fire area with a large number of high-expansion foams in a dense state and block the flow of new air to suffocate the fire with the combined effect of flooding and covering.
The fire extinguishing mechanism of the medium-expansion foam system depends on its expansion ratio and the method of use. When it is used to extinguish the fire of Class A, B, and C liquids at a lower expansion, its fire-extinguishing mechanism is the same as that of the low-expansion foam. When it is used for fire extinguishing in the way of total flooding at a higher multiple, its fire extinguishing mechanism is the same as that of high-expansion foam.
The main fire extinguishing mechanism of the low-expansion foam system is to achieve the purpose of extinguishing the fire through the covering, cooling, and suffocation of the foam layer.
Foam fire pumps and foam liquid pumps
The selection and setting of the foam fire pump shall meet the following requirements:
- A water pump with a flat characteristic curve should be selected, and its working pressure and flow should meet the system design requirements;
- A pressure gauge and a one-way valve should be installed on the pump outlet pipeline, and a pressure-maintaining pressure relief valve and a return pipe with a manual control valve should be installed on the pump outlet main pipeline;
- When the foam liquid pump is driven by a water turbine that does not drain water, the pressure loss of the water turbine should be included in the lift of the foam fire pump; when the foam liquid pump is driven by a water turbine that does not drain water, the water flow consumed by the water turbine It should be included in the rated flow rate of the foam fire pump.
The selection and setting of the foam liquid pump shall meet the following requirements:
- The working pressure and flow of the foam liquid pump should meet the system design requirements, and at the same time, ensure that the foam liquid supply pressure is greater than the water supply pressure within the design flow range;
- The structural form, seal, or packing type of the foam liquid pump should be suitable for transporting the selected foam liquid, and its material should be resistant to foam liquid corrosion and not affect the performance of the foam liquid;
- When used for ordinary foam liquid, the allowable suction vacuum height of the foam liquid pump shall not be less than 4m; when used for anti-alcohol foam liquid, the allowable suction vacuum height of the foam liquid pump shall not be less than 6m, and the foam liquid storage tank The length of the pipeline to the foam liquid pump should not exceed 5m, and the length of the outlet pipe of the foam liquid pump should not exceed 10m. The foam liquid pump and pipeline should not be filled with foam liquid at ordinary times;
- Except for the foam system set up in independent oil depots and oil product stations of level 4 and below, and a single non-important protection area with a protection area of less than 200 square meters, a backup pump should be installed, and the working pump should be able to automatically and manually switch to the backup when the working pump fails Pump;
- The foam liquid pump should be able to withstand no-load operation for no less than 10 minutes.
Foam proportioner (device)
The selection of a foam proportional mixing device should meet the following requirements:
- For fixed systems, balanced, mechanical pump-in, capsule-type pressure proportional mixing devices, or pump direct injection proportional mixing processes should be selected. The mixing ratio type should be consistent with the selected foam liquid, and the mixing ratio should not be less than the rated value;
- For fixed-roof storage tanks, external floating-roof storage tanks, and internal floating-roof storage tanks with a single tank capacity of not less than 5000m³, a balanced or mechanical pump-in proportional mixing device should be selected;
- For the fully submerged high-expansion foam fire extinguishing system or the partial application of medium-expansion and high-expansion foam fire extinguishing systems, mechanical pump-in, balanced, or capsule pressure ratio mixing devices should be selected;
- The foam-water spray system with the same or similar flow rate of the foam mixture in each zone should adopt the pump direct injection proportional mixing process;
- To protect the foam spray system of the oil-immersed transformer, a capsule pressure proportional mixing device can be selected.
Foam storage tank
The storage tank containing the foam liquid shall be made of corrosion-resistant materials, and the inner wall or lining in direct contact with the foam liquid shall not have adverse effects on the performance of the foam liquid.
Atmospheric pressure foam liquid storage tanks shall meet the following requirements:
- There should be a space for thermal expansion of the foam liquid and the space occupied by the settlement loss of the foam liquid in the storage tank;
- The setting of the liquid outlet of the storage tank should ensure that the inlet of the foam liquid pump is under positive pressure, and the liquid outlet should not be higher than the minimum liquid level of the foam liquid storage tank by 0.5m;
- The suction port of the foam liquid pipeline of the storage tank should face downward and should be set above the settlement layer, and when protein foam liquid is used, the distance between the liquid suction port and the bottom surface of the foam liquid storage tank should not be less than 0.15m;
- The storage tank should be designed with a conical or arched roof, and the upper part should be equipped with a breathing valve or lead to the atmosphere with an elbow;
- The liquid outlet, liquid level gauge, feed hole, slag discharge hole, manhole, and sampling port should be set on the storage tank.
The remaining amount of foam liquid should be marked on the storage tank of the bladder pressure proportional mixing device.
The foam liquid contains inorganic salts, hydrocarbon and fluorocarbon surfactants, and organic solvents. Long-term storage will corrode metals such as carbon steel and dissolve, swell, and penetrate many non-metallic materials. On the other hand, certain materials or anti-corrosion coatings harm the performance of the foam, especially carbon steel, which has the greatest impact on the performance of the aqueous film-forming foam. Therefore, when selecting the material or anti-corrosion coating of the inner wall of the foam liquid storage tank, special attention should be paid to whether it is suitable for the selected foam liquid. At present, the bladder-type pressure proportional mixing device has the situation that the foam liquid is stored outside the bladder, and the storage tank containing the foam liquid mentioned in this article is intended to cover such situations. Materials such as stainless steel and polytetrafluoroethylene can meet the requirements for storing various foam liquids.
foam generator
Low-expansion foam generators shall meet the following requirements:
- For fixed-roof storage tanks and internal floating-roof storage tanks, vertical foam generators should be used;
- The outer floating roof storage tank should choose a vertical foam generator that matches the foam diversion cover, and no sealing glass should be installed. When a horizontal foam generator is used, the suction port should be circular;
- The foam generator should be made of carbon steel or stainless steel according to the corrosion characteristics of its application environment;
- The nominal pressure of the vertical foam generator and its accessories shall not be lower than 1.6MPa, and it shall be connected with the pipeline by a flange;
- The working pressure at the inlet of the foam generator should be ±0.1MPa of its rated value;
- The air suction port of the foam generator and the open-air foam injection port should be equipped with a metal mesh to prevent foreign matter from entering.
High-expansion foam generators shall meet the following requirements: - The inlet working pressure should be within the calibrated working pressure range;
- The outlet working pressure should be greater than the sum of the resistance of the foam pipe and the hydrostatic pressure in the tank;
- The expansion ratio should not be less than 2, and should not be greater than 4.
The working pressure of foam nozzles and water mist nozzles should be within the calibrated working pressure range, and should not be less than 80% of their rated pressure.
control valves and piping
- The control valves used in the system should have obvious opening and closing signs.
- When the diameter of the outlet pipe of the foam fire pump is greater than 300mm, manual valves should not be used.
- The water-foam mixture and foam pipes of the low-expansion foam fire extinguishing system should be made of steel pipes, and the outer wall of the pipes should be treated with anti-corrosion.
- The dry pipeline of the medium and high multiple foam fire extinguishing systems should use galvanized steel pipe; the wet pipeline should use stainless steel pipe or steel pipe with internal and external anti-corrosion treatment; the connection between the medium multiple and high multiple foam generator and its pipeline filter The pipe shall be made of austenitic stainless steel pipe.
- The foam liquid pipeline should adopt austenitic stainless steel pipe.
- In areas with freezing conditions in the cold season, antifreeze measures should be taken for the wet pipes of the foam fire extinguishing system.
- The pipes of the foam-water spray system should be hot-dip galvanized steel pipes, and the settings of the alarm valve group, water flow indicator, pressure switch, terminal water test device, and terminal water discharge device should comply with current relevant regulations.
- Flange gaskets in fire dikes or protection areas should be made of non-combustible or flame-retardant materials.
