According to the requirements of Gb51251-2017, the smoke control and smoke exhaust systems should adopt pipes for air supply, and civil air ducts should not be used. Therefore, the installation of air duct in the civil well has become a new installation task in each project.
Technical Standard for Building Smoke Control and Smoke Exhaust System GB51251-2017 Article requirements:
3.3.7 Mechanical pressurized air supply system shall adopt pipe air supply, and civil air duct shall not be used. Air supply pipe should be made of non-combustible material and the inner wall should be smooth. When the inner wall of the air supply pipe is metal, the design wind speed should not be greater than 20m/s; When the inner wall of the air supply pipe is non-metallic, the design wind speed should not be greater than 15m/s; The thickness of air supply pipe should comply with the current national standard "Ventilation and air conditioning engineering construction quality acceptance code" GB50243 provisions.
4.4.7 Mechanical smoke exhaust system shall adopt pipe smoke exhaust, and civil air duct shall not be used. Smoke exhaust pipe should be made of non-combustible material and the inner wall should be smooth. When the inner wall of the exhaust pipe is metal, the design wind speed of the pipe should not be greater than 20m/s; When the inner wall of the smoke exhaust pipe is non-metallic, the design wind speed of the pipe should not be greater than 15m/s. The thickness of smoke exhaust pipe should be carried out in accordance with the relevant provisions of the current national standard GB50243 "Ventilation and air conditioning Engineering Construction Quality Acceptance Code".
In previous design projects, often appear well inside duct is apart from the distance of the wall is insufficient, can't meet the demand of construction, to standardize the shaft size set metal duct shaft in practice, after consulting with construction unit communication, compiled the following guidelines (scope of application: suitable for thin plate without flange duct, namely total duct flange).
The installation of metal air ducts in civil shafts follows the principle
1. When metal air ducts are installed in civil construction shafts, in order to reduce the installation difficulty of air ducts and reduce the size of civil construction air shafts, the shaft wall should be built by back wall as far as possible. When the back wall is used, it should be indicated on the architectural drawings that the wall should be built after the installation of professional air ducts.
2. The construction sequence of metal air duct in the shaft should be reinforced concrete wall, plate → metal air duct → brick wall of the building.
3. The air shaft should try to avoid concrete walls on three sides, so it is difficult to install air ducts in such cases, and the space reserved for installation is large, which has a relatively large impact on the area.
Air duct installation space reservation principle
A. When connecting the air duct, bolts should be connected at the four corners of the air duct connection, and the reasonable installation space of bolts on the four corners of the air duct should be considered during installation. The cuttings or spring clips on the four sides of the air duct can be installed on the outside of the air duct connection and pushed to the appropriate position by using tools, so there is no need to reserve personnel to enter the required installation and operation space in the other areas.
B. In the case that three sides of the shaft wall of the air shaft are built after, the bolts at the four corners of the air pipe connection are easy to install, so only 150mm space is reserved between the air pipe and the concrete wall for installation.
C. For both rear shaft walls, if the length or width of the air duct is not more than 500mm, the installation personnel can install the air duct connecting bolts at the corner outside the air duct, and only need to reserve 150mm space on both sides of the air duct; If the length and width of the air duct are both over 500mm, the installation personnel need to enter the space between the air duct and the wall to connect the air duct in the corner. Therefore, the distance between the air duct on one side and the wall should be no less than 350mm. This side can be the shorter side of the air duct, which can save installation space
D. If only one wall of the air shaft can be built back, and the length or width of the air duct is less than 500mm, 350mm installation space should be reserved on one side of the air duct for installation personnel to connect the rear side air duct; If the length of both sides of the air duct exceeds 500mm, reserve 350mm of installation space on both sides of the air duct so that the rear corner bolts of the multi-air duct can be connected to the rear side.
E. When multiple air ducts are installed in a shaft, the distance between air ducts and the distance between air ducts and the wall should also be determined according to the above principles.
F. If the building is not a high-rise building, the vertical length of the air duct shall not exceed 30m. If conditions permit, the air duct shall be connected in the no-wall area at the top of the air shaft from the upper part into the shaft, and be fixed after it is in place, the distance between the air duct in the air shaft and the concrete wall shall not be less than 100, and the distance between the air duct and the back wall shall not be less than 50mm.
Principle of leaving holes in the structural floor of civil air shaft
1. The holes in the structural plates of the air shaft should not be based on the size of the air shaft. Due to the large installation space of the air pipe, the large holes in the plate will cause inconvenience and potential safety hazards during installation.
When the distance between the air duct and the inner wall of the air shaft is less than or equal to 100mm, the floor retaining cavity should be left to the inner wall of the air shaft; when the distance between the air duct and the inner wall of the air shaft is greater than 100mm, the floor retaining cavity should be only 100mm larger than the air duct, and the floor plate should be kept 250mm beside the structure wall to facilitate the installation of the air duct.