What is Duct Fabrication? Design & Process 

Ducts are the essential components in HVAC systems, responsible for airflow circulation between the spaces. Additionally, there are industrial ducts too, which are used to exhaust the contamination and control the air quality. 

Metal fabrication is one of the main techniques to produce HVAC & industrial ducts. Galvanized steel, aluminum, stainless steel, low-carbon steels, and other metal sheets are cut, bent, and assembled for duct fabrication. 

This article will discuss the duct design, material selection, and fabrication process in detail. 

What is Duct Fabrication?

Finishing of sheet metal duct

A duct refers to the hollow channels & tubes that circulate (or distribute) the heated, cooled, or ventilated air into the desired space. On the other hand, industrial ducts transfer fumes and polluted air from the processing area.

The sheet metal ductwork fabrication involves shaping the raw metal sheets into round, rectangular, spiral, or any other shape of hollow tubes for HVAC applications.

Moreover, fabrication makes precise and perfectly fitting components for sheet metal duct installation, including duct angles, cleats, caps, corners, couplings, air return boxes, and duct transitions. 

Types of Duct Materials for Fabrication 

Based on the application environment, airflow characteristics, and size of the HVAC ducting system, you can select a suitable material from aluminum, stainless steel, galvanized steel, copper, and others.

The table below outlines the common duct fabrication materials, their properties, and examples of their applications.

Considerations for Sheet Metal Duct Design

duct design

Consider the following fundamental principles when designing the sheet metal air duct system. 

Choose between Flexible Vs Rigid Ducts 

Flexible ducts are made of flexible coil or wire enclosed with flexible sheets. On the other hand, rigid ducts are non-bendable and have a complex shape, such as rectangular and cylindrical hollow structures. 

Consider Airflow & Duct sizing 

Determine the weight of air that will flow through the duct, as it is the primary factor in deciding the duct size. When determining airflow, consider factors such as speed, pressure, air density, and other related parameters.

Integration of Duct Components 

Identify all the components and accessories for the desired ductwork and consider their integration. You must ensure that all the components will be joined/installed seamlessly.

Select the Duct Shape

Choose between round, rectangular, and round duct shapes; whatever fits best for your application. Round-shaped designs are suitable for efficient airflow and low pressure loss. Rectangular ducts are good for space-limited installations, and oval shapes are ideal for compact designs.

The Process of Duct Fabrication 

The Duct Fabrication process starts with creating a detailed engineering design & choosing a suitable metal sheet. Then, sheets are cut and shaped with metal forming methods. Ultimately, welding or other joining techniques are employed for assembly.

Let’s look at the individual steps.

• Duct Design: Creating a detailed ductwork design, outlining all features and dimensions. Also, choose the material type and sheet thickness. 
• Sheet Cutting: This process involves cutting large sheets into smaller pieces or specific profiles using precision cutting techniques, such as CNC laser cutting. 
• Metal Forming: Metal sheets are shaped using multiple metal forming methods, including bending, punching, and stretching. 
• Joining: Individual formed components are assembled together to achieve the desired duct shape. 
• Post-processing: Surface treatment and finishing operations are applied to enhance the corrosion resistance and appearance.

 Advantages of Duct Fabrication 

Sheet metal fabrication methods allow the formation of ducts with uniform air distribution, which is beneficial for thermal comfort. There is no risk of air leakage or gaps in the installation, as you can fabricate custom ducts matching the space layout.

Fabricated ductwork networks are easy to install and last for several years with minimal maintenance. Meanwhile, different finishes can be applied for aesthetic purposes. 

Conclusion  

To fabricate the sheet metal ducts, you first need a manufacturable design optimized for the desired airflow distribution. You can consider the duct type, shape, size, airflow amount, and other related parameters in the design. Meanwhile, it is essential to select the appropriate forming techniques to shape the sheets into a duct, ensuring the final result is precise & defect-free. 

Moreover, you can also partner with a reliable manufacturer for sheet metal services if you are not fabricating on your own.