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Industrial chimney structure classification characteristics and standard requirements
1. The tower type chimney can be determined according to the number of exhaust pipes. For steel towers with higher height and wider bottom, it is better to add tie rods on each side of the bottom.
2. The height of the steel tower can be in the form of single slope or multiple slopes. The ratio of the width and height of the bottom of the tower should not be less than 1/8
3. When the steel tower and the exhaust stack are hoisted as a whole, the hoisting calculation of the tower should be carried out.
4. The tower should calculate the wind vibration impact caused by pulsating wind. When the basic natural vibration period of the tower is less than 0.25, the wind vibration impact will not be calculated.
5. For the steel tower foundation that bears uplift force and lateral force, in addition to the strength calculation and deformation check of the foundation, the pullout and anti-sliding stability check should also be carried out.
6. When the tower platform is connected to the exhaust stack, a slideway type connection can be used.
7. The tower should have transverse partitions along the tower surface where the slope changes or where the stress conditions are complex and the structure is weak. In the rest, transverse partitions can be set up every 5 sections along the height of the tower. A rest platform or maintenance platform should be provided every 30m along the height of the tower.
1. The relationship between the diameter of the self-standing chimney and the height of the corresponding position should be determined after calculation based on the strength and deformation requirements, and should meet the diameter of the lower part of the chimney and adopt other tension shock absorption and measures.
2. Under the action of bending moment and axial force, the local stability of the chimney should be checked based on the maximum bending moment, horizontal seismic action and corresponding axial pressure action.
3. Under the action of bending moment and wheelbase force, the axial stability coefficient and overall stability of the welded cylindrical section of the chimney are calculated according to the cantilever structure.
4. The thickness of the insulation layer should be determined by temperature calculation, and the minimum thickness should not be less than 50mm. For fully radiant furnaces, the thickness of the chimney insulation layer should not be less than 75mm.
5. When the chimney flue gas temperature is higher than 560 degrees, the uranium fasteners of the heat insulation layer can be made of stainless steel (1Cr18Ni9Ti).
6. When the critical wind speed of the chimney is less than 6m/s, a wind-breaking circle should be installed. The critical wind speed of the chimney is 7m/s~13m/s, which is lower than the design wind speed. If it is uneconomical to change the distance, diameter and thickness of the chimney, a wind breaking circle can also be installed.
1. When the ratio of cable-type chimney height to diameter is greater than 30 (h/d>>30), cable-type steel chimneys can be used.
2 When the ratio of chimney height to diameter is less than 35, a layer of cables can be installed. There should be three cables, the angle between the planes should be 120 degrees, and the angle between the cables and the chimney axis should not be less than 25 degrees.
3. When the ratio of chimney height to straightness is greater than 35, two layers of cables can be set up. The upper cable tie position should be less than h/3 from the top of the chimney, and the lower cable tie position should be located from the upper cable to the chimney. At 1/2 height of the bottom.
4. The calculation of the internal force of the cable-type chimney under wind load and earthquake action can be based on the national standard "Code for Design of Towering Structures" GB-50135 and the influence of cross-wind vibration should be taken into account.
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