Why does a gas fire extinguishing system have a pressure relief vent?

First, the actual significance of gas fire extinguishing installation pressure relief device: According to GB50370-2005 "gas extinguishing system design specifications" requirements, heptafluoropropane fire extinguishing system fire extinguishing design concentration is generally 8% to 10%. When heptafluoropropane fire extinguishing agent is released into a completely sealed protection zone, the release of driving gas (nitrogen) and heptafluoropropane fire extinguishing agent at 20°C under standard atmospheric pressure, vaporization increases the pressure in the protection zone, and the chemical absorbs part of the heat, so that The temperature in the protected area is reduced, which results in a small pressure drop. The increase in pressure is mainly related to the degree of containment of the protected area and the design concentration of the fire extinguishing and the leak tightness of the pressure relief port (automatic pressure relief device). The pressure increase value is basically equal to the volume concentration ratio of the fire protection design in the protection zone. The increase value is 8 to 10 kPa. This pressure value will exceed the 6 to 8 times of the 1.2 KPa of the light, high-rise buildings and ordinary buildings.

In the well-sealed 108m3 test room, the pressure relief port opening operation test was performed. The opening pressure was set to 1.1+0.1KPa, the theoretical calculation test nitrogen pressure was 1.45MPa, and the actual test pressure value was 3.8MPa, which was 2.62 times higher. This indicates that the fire suppression design of a small concentration of heptafluoropropane fire extinguishing system, if the protective zone is good sealing, the pressure value of the protection zone after gas release can still exceed 1.2KPa, which will cause damage to the enclosure structure in the protection zone, resulting in the system can not be normal Extinguishing.

In the IG-541 mixed gas fire extinguishing system, the fire extinguishing design concentration is 37.5% to 43%; in the carbon dioxide gas fire extinguishing system, the fire extinguishing design concentration is between 34% and 62%. In other words, when the two fire extinguishing agents are released into the fully enclosed protection zone, the gas volume in the protection zone will rapidly expand, and the pressure value in the protection zone will exceed 25 times the allowable pressure of 1.2 KPa, enough to destroy the protection zone. The entire enclosure structure. A company in the 6m long, 6m wide, 4m high test room to do IG-541 mixed gas test, the protective zone opened a diameter Φ200mm vents, exhaust fans on the normal work, when sprayed into the laboratory 7 bottles 70 When the IG-541 mixture gas was raised, the door of the laboratory was opened and the exhaust fan was seriously deformed.

Second, GB50370-2005 "gas extinguishing system design specifications" requirements

In the GB50370-2005 "Gas Fire Extinguishing System Design Code" issued on March 2, 2006, the terms of the design terms and the formula for the pressure relief port area of ​​the protected area are used in terms of terms, regardless of whether the sealing of doors and windows in the protected area is good or poor. Whether the protection zone door is installed with an open spring door or a flexible door closer, if a gas fire extinguishing system is used, a pressure relief port must be installed in the protection zone. The pressure relief vent is not an opening but a pressure relief device. This device is normally closed. When it reaches or approaches the allowable pressure value of the protection zone, it will automatically open and release pressure. When it is lower than the set pressure value, it will automatically shut down to avoid the loss of extinguishing agent and affect the normal fire extinguishing effect.

In recent years, many key projects and projects using pressure relief outlets have high requirements on the accuracy of temperature and humidity in the protection zone. Therefore, the sealing requirements for the protection zone are also very high. Therefore, the GB50370-2005 National Standard for Design of Gas Fire Extinguishing Systems stipulates that pressure relief vents should be designed and installed in the protective areas using gas fire extinguishing systems. The revised new standard amended the ambiguous terms in the old standards and specifications. In all levels of fire inspection, the fire inspection and supervision departments are strictly in accordance with the new standards. If a gas fire extinguishing system is installed in the fire protection project, it is first necessary to check whether the pressure relief ports (automatic pressure relief devices) are installed in each protection zone.