Fabrication And Construction of Sheet Metal Duct

As we all know, the materials of the sheet metal air duct are different, and the processing methods are also different. However, most of the production and installation processes are similar. In real life, the most common is the iron sheet ventilation pipe. Due to its mechanized processing method, it has become the first choice more suitable for most occasions.
Next, let’s introduce the complete production process of the iron sheet air duct in detail.
Blanking And Beading Sheet Metal Duct
1. In the processing workshop, the thickness of galvanized steel plate shall be selected according to the prepared material list of air duct, the galvanized steel plate shall be loaded into the leveling and pressing machine from the feeding frame, and the end of the steel plate shall be cut off after startup. During feeding, check whether the steel plate is inclined, try to cut a steel plate, and measure whether the cut line of the cut steel plate is perpendicular to the sideline and whether the diagonal line is consistent.
2. Input the blanking length and quantity in the material list into the computer, start the machine, and the computer will automatically cut and press the reinforcement. The material used for plate cutting must be rechecked to avoid errors.
3. The plates with special shapes shall be cut with a HARSLE-4015 plasma cutting machine, and the sporadic materials shall be cut with on-site electric scissors. When using the fixed dynamic shear, hold the steel plate with both hands, the hand shall not be less than 5cm away from the knife-edge, and the force shall be uniform and appropriate. Sheet Metal Duct
Chamfer And Locking
For the sheet metal air ducts connected by bite, the bite width and allowance are determined according to the plate thickness. The bite width is shown in the table below: Sheet Metal Duct
Sheet Thickness(mm) | Angle Lock Width(mm) | Flat Lock Width(mm) |
0.75 | 8~10 | 7~8 |
1.0~1.2 | 10~12 | 9~10 |
1.5 | 12~14 | 10~11 |
Flange Machining
Connection method of angle steel flange: the flange is assembled and welded by four-angle steel. During marking and blanking, it shall be noted that the inner diameter of the welded flange shall not be less than the outer diameter of the air duct, and shall be cut off by the grinding wheel cutter according to the line; After blanking and straightening, put it on the drilling machine to drill rivet holes and bolt holes.
The hole spacing of the ventilation and air conditioning system shall be greater than 150m, and the hole spacing of the smoke exhaust system shall not be greater than 100mm. The punched angle steel shall be evenly divided and placed on the welding platform for welding. During welding, it shall be clamped and flattened according to the molds of various specifications. After welding, bolt holes shall be drilled on the bench drill; The bolt hole spacing is the same as the rivet hole spacing and evenly distributed. Sheet Metal Duct
Air Duct Folding
The sheet metal after undercut shall be placed on the folding machine according to the drawn folding line and placed on the centerline of the lower die. During operation, make the centerline of the upper folded square piece of the machine coincide with the center of the lower die and fold it into the required angle.
When folding, they shall cooperate with each other and keep a certain distance from the folding machine to avoid being hurt by the overturned steel plate or counterweight.
Air Duct Seaming
The sheet metal air duct finished by biting shall be sewn with a hand-held electric seaming machine. The appearance quality of the sewn air duct shall be straight, the arc shall be uniform, the two ends shall be parallel without warping angle, and the surface concave-convex shall not be greater than 5mm.
Install Angle Flange
When the sheet metal air duct are combined with the flange, the allowable deviation is shown in the table below:
Length | Deviation | Allowable Deviation Inside Flange | Allowable Flatness Deviation | Diagonal Allowable Deviation |
≤300mm | -1~0mm | +1~+3mm | 2mm | ≤3mm |
≥300mm | -2~0mm | +1~+3mm | 2mm | ≤3mm |
Before riveting the sheet metal air duct and the flange, the technical quality shall be reviewed first. After it is qualified, the flange shall be sleeved on the air duct. The straight line of the air duct shall be perpendicular to the flange plane, and then the hydraulic rivet pliers or manual eye clamp shall be used for 5 × 10 rivets the air duct and turn it around; Sheet Metal Duct
The flange shall be flat, not less than 6mm, the four corners shall be leveled, and there shall be no gap to avoid air leakage. The minimum thickness of the plate and the minimum specification of the hanger are as follows:Sheet Metal Duct
Air Duct Length B | Round Duct | Rectangular Duct | Smoke Exhaust Duct | Boom Diameter | Angle Steel | U-Steel |
B≤320 | 0.5 | 0.5 | 0.75 | 8 | 25×3 | 40×20×1.5 |
320<B≤630 | 0.5 | 0.6 | 0.75 | 8 | 25×3 | 40×40×2.0 |
630<B≤1000 | 0.75 | 0.75 | 1.0 | 10 | 30×4 | 40×40×2.0 |
1000<B≤2000 | 1.2 | 1.0 | 1.2 | 10 | 40×4 | 60×40×2.0 |
2000<B≤4000 | 1.2 | 1.2 | 1.2 | 10 | 50×5 | 60×40×2.0 |
Construction Steps
TDF Flange
The common plate flange has the characteristics of low cost, good sealing performance, and convenient and simple installation. It is especially suitable for the production of ventilation pipes with a small cross-sectional area. Because the flange is bent by the galvanized steel plate itself, it has the advantages of being lightweight, good sealing, and convenient manufacture and installation. Sheet Metal Duct
The basic requirements are the same as the angle steel flange air duct. The basic requirements for the manufacture of a common plate flange air duct are the same as that of an angle steel flange air duct. After the plate impact angle and bite, it enters the common plate flange machine to press the flange. Sheet Metal Duct
The semi-finished products after pressing the flange shall be transported to the construction site, the flange corners shall be folded, stitched, and installed, the flange surface shall be leveled, the diagonal error of the air duct shall be inspected, and finally, the four corners shall be sealed with sealant. Sheet Metal Duct
Fabrication of Stainless Steel Air Duct
When making a stainless steel sheet metal air duct, the plate shall be spliced by argon arc welding. During welding, the welding materials shall be matched with the base metal, and the surface shall be prevented from being polluted by welding spatter. After welding, the welding slag and spatter shall be removed.
After the fabrication of the air duct, all welds shall be pickled and passivated to prevent rust. The minimum thickness of stainless steel air duct plate and flange specification are as follows: Sheet Metal Duct
Air Duct Length B | Stainless Sheet Thickness(mm) | Angle Steel Type | Bolt Specification |
B≤320 | 1.0 | 25×3 | M6 |
320<B≤630 | 1.0 | 25×3 | M6 |
630<B≤1000 | 1.0 | 30×4 | M8 |
1000<B≤2000 | 1.2 | 40×4 | M8 |
2000<B≤4000 | 1.2 | 50×5 | M10 |
All connections between stainless steel air duct adopt flange connection. The flange is made of stainless steel flat steel, and the connection between the flange and the air duct adopts argon arc welding.
Clean Air Conditioning Duct Operation
The manufacturing sequence of ventilation pipes, fittings, and components is plate handling, cleaning oil stain, making bite, folding, removing oil stain on the surface, combined riveting forming, scrubbing the inner surface, inspecting the closed nozzle, and stacking of finished products. Control points of ventilation duct fabrication and processing technology: Sheet Metal Duct
1. The plate shall be provided with a material certificate, and the appearance inspection must be flat, smooth, free of scratch and zinc layer peeling, and meet the design requirements, otherwise it shall not be used.
2. Before processing, remove the oil stain on the plate and do one touch, two wipes, and three checks to ensure that the oil stain is completely removed. Sheet Metal Duct
3. In the process of processing, in order to prevent the iron sheet from being scratched and worn, damaging the zinc layer, or contaminated with dust, a 3mm thick rubber plate is paved on the flat cement floor, and the blanking is carried out on the rubber plate.
4. When cutting, undercutting, splicing, folding, and transporting sheet materials, the storage rack or four-wheel trolley shall be used to receive and transfer the materials, and shall not touch the ground and drag; Semi-finished products are stacked on the platform with a rubber plate. Sheet Metal Duct
5. Key points of flange processing control: the profile must meet the high-quality standard and shall not be rusted, skinned, or pitted; The flatness of the flange welding joint shall not be greater than 0.5mm, the rivets must be galvanized, the rivet spacing shall not be greater than 100mm (screw hole spacing shall not be greater than 12mm), the hole spacing shall be accurate and interchangeable; Welding slag, welding spatter and floating rust shall be completely removed; Apply anti-rust primer with strong adhesion for two times, and there shall be no paint dripping in screw holes and corners. Sheet Metal Duct
6. For the combination of semi-finished products of inner pipes, components, and accessories, the dirt at the site shall be removed first. After the combination riveting, the gaps and holes shall be blocked with glue or tin. The flange width is consistent, greater than 7mm, and the screw hole is not covered; The flatness is less than 1mm. The finished products shall be stored horizontally by category, and attention shall be paid to protect the paint from wear; For the air duct to be reinforced, the stiffener is only allowed to be set on the outer wall. Sheet Metal Duct
7. The air duct components and accessories are manufactured in the form of single bite, corner bite, joint bite, etc.
8. When making the sheet metal air duct, the material shall be cut according to the plate to minimize the joints. The specific provisions are as follows: there shall be no joints within 800mm of the bottom edge width of the rectangular air duct, there shall be only one joint within 800mm-1000mm, and there can be two joints within 2400mm. Transverse splicing is prohibited for all the above dimensions, and the ratio of the long side to the short side of the rectangular air duct shall not be greater than 4:1; Sheet Metal Duct
The butt joint shall be of a single flat type. Pay attention to placing the flat surface of the butt joint on the inner wall of the pipe without reversal during the corner butt joint; The flexible short pipe shall be made of a soft rubber plate or high-quality artificial leather. The inner wall shall be smooth, the longitudinal joint shall be glued smoothly, and there shall be no holes or glue leakage gaps. Sheet Metal Duct
9. Cleaning of air duct: the cleaning of the air duct is particularly important. Generally, the galvanized steel plate has not been decreased, and the surface of the steel plate is coated with a large amount of grease. If it is not cleaned, it will be contaminated with dust during transportation, installation, and subsequent operation. During long-term use, it may lead to dust accumulation and flying, resulting in a sudden increase in the dust concentration in the air in front of the filter, This has a very adverse impact on the use of high-efficiency filters.
Cleaning is mainly dust removal and degreasing. Clean water or pure water plus neutral cleaning agent shall be used for dust removal, and trichloroethylene or industrial alcohol shall be used for degreasing. Sheet Metal Duct
Cleaning sequence: clean with clean water or pure water, wash with the neutral cleaning agent, use trichloroethylene or industrial alcohol decreasing water or pure water to wash clean cloth, scrub white silk cloth for inspection (it is qualified if it does not change color).
The qualified air duct shall be sealed with plastic film immediately.
10. After the air duct is processed and manufactured, it shall be carefully and comprehensively inspected. After passing the handover inspection and acceptance, it shall be sealed with high-quality flexible plastic film. The sealing part shall be tightly bound with adhesive tape, and then stacked by category.
Installation of FRP Air Duct
1. For flange connection of FRP air duct, the flange bolt spacing shall not be greater than 120mm, the flange spacing shall be uniform, the flange shall be flat, and the thickness of flange gasket shall be 3 ~ 5mm.
2. When the length of the FRP air duct exceeds 20m, there should add at least one fixed support.
3. The connecting bolts of the FRP air duct are galvanized bolts, and galvanized plain gaskets are added on both sides of flange bolts.
4. The flatness of the FRP air duct flange shall not be greater than 3mm, the size deviation of the air duct shall not be greater than 3mm, and the diagonal size deviation shall not be greater than 5mm.
5. The connection between FRP air duct and air outlet shall not be opened on-site, but shall be prefabricated during processing and fabrication.
Sheet Metal Duct Reinforcement
1. When the large side size of the sheet metal air duct is 630 ~ 1000mm, the reinforcement shall be directly pressed on the production line, the arrangement shall be regular, the spacing shall be uniform, and the plate surface shall not have obvious deformation.
2. When the large side size of the air duct is more than 1000mm, angle steel, flat steel, steel pipe, z-groove, reinforcing bar, through wire screw, etc. can be used for internal and external reinforcement of the duct.
3. For the reinforcement of angle steel or reinforcing bar, its height shall be less than or equal to the height of air duct flange, the arrangement shall be neat, the spacing shall be uniform and symmetrical, and shall not be greater than 220mm, and the riveting with air duct shall be firm.
4. The pipe shall be supported and reinforced with through wire screw. Its special gasket shall be placed on the inner wall of the external insulation air pipe. For non-insulation air pipe or internal insulation air pipe, it shall be placed on the outer wall of the air pipe. The through wire screw shall be set at the center of the air pipe. When the cross-section of the air pipe is large, a through wire screw shall be added on both sides close to the flange for support and reinforcement.
5. When the section of the air duct is more than 1250 * 630, in order to keep the adjacent walls perpendicular to each other, 90 ℃ inclined support should be used at the four corners of the air duct for reinforcement.
6. When the length of the air duct of medium pressure and the high-pressure system is greater than 1250mm, a reinforcement frame shall be used for reinforcement.
Different occasions make the production project party choose different materials and different types of ventilation pipes. However, due to the similarity of the ventilation duct, we will find that no matter how the air duct evolves, its basic framework and supporting elements are fixed. This also determines the high relevance of air duct production, processing, and installation.
Only by reasonably following the production and installation steps can improve the project efficiency.
Acabo de recibir un sitio de construcción con un total de aproximadamente 100.000 metros cuadrados de conductos de aire. ¿Qué tipo de máquinas eficientes se necesitan para la producción? Por favor deje su información de contacto. Me gustarÃa consultar en detalle.
El monto de este proyecto no es pequeño, si no hay lÃmite de tiempo, tengo un plan de ahorro de costos y tomaré la iniciativa para contactarlos.