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Calculation method of pressure relief port area

Release time:2014-03-12 viewed:0

[students] vent area calculation method of pressure?

[answer] in compressive strength envelope and a pressure relief opening problem, we consider the set pressure relief port must be exactly meet the maximum in the agent application when the internal pressure does not exceed the bearing capacity of retaining structure in the weakest component, but retaining structure is the weakest link in the bearing capacity and the maximum fine dry powder fire extinguishing agent when spraying the internal pressure in the practical application are very difficult to determine or judge, in order to ensure that the envelope agent application of safety in the super fine powder, we need to calculate the area of the pressure relief in accordance with the standard pressure port allows smaller, or set up in accordance with the internal pressure automatic regulating vent relief area, or set pressure retaining structure in lower capacity than the precast whole original envelope in the weakest member weak component.

Here need to remind is, many fine dry powder fire extinguishing system of local standards have not involved the pressure relief port problems, such as the Hubei DB42/294-2004 "fine dry powder fire extinguishing system design, no network construction and acceptance standard of" no provisions in the pressure relief port settings, the article said: "allow the pressure in the provisions of this on the protection zone of the doors and windows and building envelope components, equivalent to adopt the domestic gas fire extinguishing system design specification data. Superfine powder full flooding automatic fire extinguishing agent in the system with nitrogen gas drive jet, according to the calculation of solid gas ratio and the actual service condition, fire extinguishing agent is released, the pressure in the protection zone of the added value is generally less than 320Pa, the pressure is much lower than the national gas fire extinguishing system design specification of data requirements, so the standard is not required. The provisions of the pressure relief port closed space." In fact, in the later we did several fire test, had windows were a block out or breaking conditions (mainly test injection in the cabinet type superfine dry powder extinguishing device, which shows that, when) pipeless ultra-fine dry powder extinguishing device needs to set the pressure relief port, need more network fine dry powder fire extinguishing system, and confirmed the previously mentioned according to the allowed pressure to calculate the pressure discharge standard area is small.

The calculation formula was visible from the GB50347 and DB37/T1317-2009 two standard vent, vent area calculation pressure opening in the enclosure structure allows the pressure given situation has considered the factors such as temperature. From the experiment we usually do can be seen, we have no combustion and combustion, the strong and the weak in different conditions of spraying superfine dry powder extinguishing agent, enclosure internal pressure is completely different. This shows that protection area in spraying superfine powder extinguishing agent when the internal pressure, not only with the superfine powder extinguishing agent spraying rate, and spraying superfine powder extinguishing agent when the internal temperature has a great relationship, therefore, in the calculation of pressure relief of considering temperature factor is necessary.

However, determinants of internal temperature protection area is a lot of, at least including: flammable substances in the protection zone of the nature, number and shape, the protection zone, the volume of fire time, not difficult relationship we give vent area temperature and pressure, but to accurately calculate the temperature inside the door area is impossible the. Therefore, we need are given in the specification for different occasions or circumstances temperature correction coefficient.

 

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