Have you ever wondered how the air ducts in your home or office are made? In this fascinating blog post, we’ll take you on a journey through the intriguing process of crafting these essential components of ventilation systems. From field measurements to the final assembly, our expert mechanical engineer will guide you through each step, revealing the precision and skill required to create efficient and effective air ducts. Get ready to discover the hidden world behind the walls and ceilings that keep you comfortable every day.
Through the above work, draw processing installation sketches.
When selecting the material for the model, it is crucial to choose one that is not too thick, ideally within the range of 1 to 3mm. The material should also be free from curling or deformation. Preferred materials include:
The length of the circular tube sample should be calculated using the following formula:Length=(Outer Diameter of Pipe+Thickness of Sample Material)×𝜋Length=(Outer Diameter of Pipe+Thickness of Sample Material)×πHowever, it is important to account for seasonal and material influences that may affect the actual circumference of the pipe. For instance:
These adjustments should be made before drawing the expansion curve, as neither growth nor reduction can be carried out afterward.
After creating the model, it is essential to verify its shape and size by wrapping it around the outer wall of the pipeline and checking the volume. The model should fit closely to the pipe wall, with the two ends meeting without any gaps or overlaps. There are three methods for expanding the model:
Blanking is a critical step in the sheet metal fabrication process, where the material is cut into a specific shape or size. This process involves marking the sheet material with the unfolding drawing and the clear outline of the blank size before proceeding to the shearing step. Here are the detailed steps and considerations for effective blanking:
Before any cutting begins, it is essential to mark the sheet material accurately:
Shearing is the process of cutting the sheet material. The method of shearing depends on the thickness of the material:
Choose the plate thickness based on the specifications and sizes of the air duct. Ensure to leave a margin for unloading to accommodate any adjustments during the manufacturing process.
The line drawing process must be precise to ensure straight angles, flat lines, and accurate measurements. Frequently check geometric sizes and ensure all necessary lines, such as cutting lines, chamfering lines, folding lines, flanging lines, hole lines, and closing lines, are drawn accurately.
Cutting and chamfering must be executed with high precision to minimize errors. After cutting, chamfer the edges using a chamfering machine or iron scissors before closing the edges. Ensure there is no overlap or flanging during the operation to maintain the integrity of the air duct.
Place the plate on the folding machine according to the drawn folding line and fold it to the desired angle. During the operation, align the folding line with the upper and lower molds of the square folding machine to ensure accuracy.
To create a round air duct, use a clapper to shape the edge into an arc. Circle the bite and adjust the arc to make it uniform. This ensures a smooth and consistent round shape for the air duct.
After folding or rounding the steel plate, use a seaming machine or manual seaming. Apply even pressure to avoid uneven seams or bursting. Proper seaming ensures the durability and functionality of the air duct.
The seams of the air duct plates should be staggered to avoid cross-shaped seams, which can weaken the structure. Proper seam staggering enhances the strength and stability of the air duct.
Steel plate duct bite joint:
Stainless steel plate duct bite joint:
Aluminum plate air duct bite joint:
The width of the bite is determined by the thickness of the air duct material. Typically, for single flat bites, single vertical bites, and single angle bites, the width of the bite on the first plate should be consistent. On the second plate, the bite width should be doubled, resulting in a total allowance for the bite equal to three times the bite width. The quantity of the bite should be maintained on both sides as required by the design specifications.
Mechanical bite processing primarily involves the use of various bite machines. For curved lines or solid bites, it is recommended to use wooden blocks and wooden hammers instead of steel hand hammers to extend the edge of the board. This practice helps avoid visible marks on the material. The joint of the bite should be tight, with no half bites or cracking.
For straight pipes, the joints should be staggered in the longitudinal bite seam. This is crucial because air ducts often include elbows, tees, and other fittings. A round elbow, for instance, is composed of several short inclined tubes, and the single bite is formed in one direction when making the elbow. Consequently, the bite seam of each section is in opposition, which is necessary for the production of elbows and is not restricted by this regulation.
The width of the bite seam should be uniform to prevent inconsistencies, such as a wide bite seam at one end and a narrow bite seam at the other. Such inconsistencies can affect both the appearance and the structural integrity and tightness of the bite seam.
Butt welding is utilized for joining plates or for creating horizontal and vertical closed seams. This method ensures a strong and seamless connection between two metal pieces, making it ideal for applications where structural integrity is paramount.
Lap welding is commonly used for the longitudinal closed seams of rectangular ducts or pipe fittings, as well as the elbows and corner joints of tees in rectangular ducts. The general overlap is 10mm, and the overlap area should be marked before welding. Spot welding should be performed along the marked line, followed by smoothing the weld with a small hammer before continuous welding. This method ensures a strong bond and minimizes the risk of leaks.
Flange welding is employed for closing joints without flanges, round pipes, and elbows. When dealing with thin sheets, gas welding can be used due to its precision and control over heat input, which prevents warping and ensures a clean weld.
Fillet welding is used for the longitudinal closed seams of rectangular air ducts or pipe fittings, the turning joints of rectangular elbows and tees, and the closed seams of round rectangular air duct heads. This type of welding provides a strong joint and is often used in applications where the weld is subjected to various stresses.
For carbon steel ducts, a DC welding machine should be used. Prior to welding, the area must be cleaned of dirt, oil marks, and rust. Both spot welding and continuous welding require the removal of oxides to ensure a clean weld. The gap should be minimized, and any nodules at the manual spot welding position should be promptly removed. After welding, electrode slag and residual welding wire in the seam and nearby areas should be cleaned to maintain weld quality.
Before welding stainless steel ducts, grease and dirt must be cleaned from the welding seam area using gasoline or acetone to prevent air holes and sand holes. During arc welding, white powder should be applied to both sides of the weld to prevent spatter from adhering to the plate surface. Post-welding, the slag should be removed, and the metallic luster should be restored with a copper wire brush. The weld should then be pickled with a 10% hydrochloric acid solution and washed with hot water to ensure a clean and corrosion-resistant weld.
For aluminum air ducts, the welding area must be degreased and the oxide film removed using a stainless steel wire brush. Welding should be performed within 2 to 3 hours after cleaning. Post-welding, degreasing should be done using aviation gasoline, industrial alcohol, carbon tetrachloride, or other cleaning agents and wood chips to ensure a clean weld.
Gas welding of thin steel plate ducts is typically performed from left to right. The flame direction should be controlled to ensure balanced heat distribution on both sides of the weld. The flame should move forward smoothly and evenly, with a uniform speed of the welding wire into the molten pool to achieve a consistent weld.
The surface of the weld should be free of defects such as cracks, burn-through, or missing welds. Longitudinal welds should be staggered to distribute stress evenly. The welding seam should be smooth, and spot welding should be symmetrically alternated to prevent deformation. The width of the welding seam should be uniform. After welding, the weld should be cleaned to remove welding slag, ensuring a clean and strong joint.
Most circular air pipes utilize either direct socket connections or core tube connections. Here’s a detailed explanation of these methods:
The connection of rectangular air pipes typically involves various methods to ensure a secure and airtight connection:
(1) Reinforcement Techniques:
Joint height reinforcement technique (using a standing bite). Reinforcing the air duct with an angle steel ring around the circumference. Reinforcing the larger side of the duct with angle steel. Longitudinally reinforcing the inner wall of the air duct with ribs and reinforcing the steel plate of the air duct with rolled grooves or crimped ribs.
Requirements for Air Duct Reinforcement Quality:
The air duct must be firmly reinforced, and for it to be considered excellent, it must be neat.
The spacing between each reinforcement must be appropriate, uniform, and parallel.
(2) Forms and Requirements for Air Duct Reinforcement:
The air duct can be reinforced in the form of corrugated bars, standing bars, angle steel (for both internal and external reinforcement), flat steel (using vertical reinforcement), reinforcing bars, and internal tube support.
Refer to Figure 4.3.1.11.
Figure 4.3.1.11 Reinforcement form of air duct
(3) Reinforcement using corrugated bars or wires should be arranged in a regular pattern with uniform intervals, and there should be no obvious deformations on the surface of the duct.
(4) Angle steel and reinforcement ribs should be arranged neatly and symmetrically, with a height not exceeding the flange width of the air duct. The riveting of angle steel, reinforcement ribs, and air duct should be secure, with even spacing not exceeding 220mm, and the two intersections should be joined as one.
(5) Supports and air ducts should be fixed securely, with uniform spacing between each support point, or the edge or flange of the air duct, not exceeding 950mm.
(6) For medium-pressure and high-pressure system air duct sections with a length greater than 1250mm, reinforcement bars should also be used. The metal air duct of the high-pressure system should have reinforcement or reinforcing measures to prevent bursting at the single bite seam.
As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.
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