What is a duct flange? Things to note when buying a ... - Tiger Steel

Recently, the keyword “duct flange” has been searched extensively, especially on technical knowledge-sharing forums. This accessory is quite new for those not in the profession. So what is a duct flange? What are its characteristics, and what should you pay attention to when buying it? This article will have the answer for you.

For more information, please visit MIDAS.

What is a duct flange?

A duct flange is a type of flange produced together with the duct by a specialized machine. This accessory is used to connect the ducts to complete the pipeline system. With that, the system is always sturdy, operates stably, and does not vibrate while transmitting air.

Depending on the cross-section of the duct, the accompanying flange will have different sizes and designs. Currently, there are 3 types of ducts commonly used on the market: flexible, round, and square. Therefore, the accompanying flange will also have corresponding structures and materials. In terms of structure, this type of flange also has holes on the body similar to the flanges we often see. And when you want to connect the details, you just need to use bolts to connect. In addition to duct flanges, there are many types of flanges used in pipeline systems. You can read more in the article: What types of flanges are popular on the market today?

Types of flanges for air ducts on the market

As mentioned, duct flanges are very diverse, both in style and design. However, to help readers easily recognize and distinguish these types of flanges, Bao Tin Steel will classify them as follows:

Classification by manufacturing materials

Based on the variety of manufacturing materials, you have the following 3 types:

• Stainless steel flange: This type of flange is used for duct systems in industrial zones and chemical production zones. Thanks to its high anti-rust and anti-abrasion properties, even when exposed to chemicals, this accessory is not affected too much.
• Steel flange: Steel is a popular material for making flanges thanks to its high durability and low abrasion. This type of flange is widely used in medium-/large-sized duct systems.
• PVC plastic flange: This type of flange is often used in plastic duct systems and is cast in one piece.

Classification by structure

Below are the types of flanges that you can easily recognize with their structural characteristics:

• Weld-on flange: This type of flange has a long neck so that when installed, it can be directly attached to the duct.
• Cage flange: This type of flange is designed with separate parts into 2 separate parts. At the same time, it has the same connection method with the pipe as the weld-on flange.
• Cast-on flange: This type of flange has a weld from the outside. The inside of the flange contains the duct. When installing, the worker needs to install so that the pipe end is a moderate distance from the cast-on part.
• Slip-on flange: This type of flange connects to the pipe similar to the cast-on flange. However, the seal is better because the thickness of the flange fits the pipe better.
• Threaded flange: This type of flange connects to the pipe thanks to threads, not thanks to welding.
• Blind flange: This type of flange is used to seal the pipeline, and there is no hole in the middle of this flange.

Duct flange standards

Duct flanges are very diverse and have different parameters and standards. It depends on the shape of the duct, whether it is square or round. Below are the figures for your reference:

Standard of a round duct flange

Diameter of circular cross-section air duct Flange material specifications Flat steel Angle steel £ 140 – 20 x 4 150 ÷ 280 – 25 x 4 300 ÷ 500 L 25 x 3 530 ÷ L 25 x 4 ÷ L 40 x 4

Square duct flange standards

Large edge length rectangular cross-section air duct Material specifications for angle steel flanges £ 630 L 25 x 3 800 ¸ L 30 x 4 ¸ L 40 x 3

Materials for manufacturing duct flanges

The materials used to manufacture this type of flange are extremely diverse, such as zinc, galvanized aluminum, stainless steel, steel, plastic, etc. Depending on the material of the pipe to be joined, the flange material will be synchronized to match. At the same time, this process also requires meticulousness and high precision. Therefore, the craftsman who manufactures this special type of flange often has to be highly specialized and experienced.

The flange typically uses the air duct’s material. This is to increase the tightness and durability of the joint. To simplify this, manufacturers often base the process the process on the available pipe to process the corresponding accompanying flange.

How to choose a standard duct flange

Not everyone knows how to choose duct flanges. Especially with large projects, factors such as materials, sizes, standards, etc. need to be paid attention to. Specifically:

• Ducts: Ducts are very diverse today. We have round, square, rectangular shapes, etc. Therefore, the accompanying flanges must also correspond to these shapes.
• Manufacturing materials: Each type of duct will be used in a different environmental condition. Its frame must also meet those conditions. This helps the duct to be durable for a long time of operation.
• Size: Because the flange will be mounted on the duct, it must fit the diameter of the duct.
• Connection type: We have connection types corresponding to flange types such as welded flanges, threaded flanges, and blind flanges. Therefore, we need to choose the flange that is suitable for the ventilation duct in each type of construction.
• Manufacturing standards: For the duct system to be durable, we need to clearly understand and choose the appropriate flange standard.
• Price: This is also a factor that many people are interested in. You need to research and refer to prices from many places to have good preparation for costs.
• Supplier: There are many different suppliers in the market. You need to understand and choose a reputable and guaranteed seller. Avoid losing money. You can contact Bao Tin Steel at 059 176 to buy guaranteed products.

What should be noted when buying duct flanges?

This flange is a pipe fitting used in many large and small projects. So what should be noted when choosing accessories for this duct system and what is the price?

Buy the right flange

As the name suggests, this type of flange always goes with the air duct. Therefore, you need to know what type of air duct you are using, its size, and its material. It will help you choose the appropriate type of flange. For example, if the air duct is made of PVC plastic, you also need to choose a

PVC plastic flange for the connection. Because only then will the connection be tight and uniform. This will bring about operational efficiency as well as prolong the life of the system.

Price of flange

There are many suppliers of flanges for duct systems on the market with different prices. These prices are not fixed and may change depending on the time or source of goods. Therefore, you need to consult the prices of flanges in general and duct flange prices in particular from reputable suppliers. From here, you will have a detailed comparison.

You also need to note that there are currently many quotes for duct flanges on the internet. This may be a trick to attract buyers from many scammers. There have been many unfortunate cases where buyers mistakenly believed and transferred the dog to these people. Therefore, you need to be vigilant and research carefully before deciding to order.

Where to buy quality duct flanges?

Bao Tin Steel is one of the suppliers of quality flanges today. In addition to materials for pipeline systems, the company also manufactures, imports, and distributes many products. Typically: steel pipes, accessories, industrial valves, and fire protection materials. If you have any questions or want to order duct flanges, please contact Bao Tin Steel immediately! We are always here and ready to support you at any time.

A split flange for pipe connects two sections without removing the entire assembly.

It clamps around the pipe in two halves, using bolts and an O-ring to create a tight seal.

This design makes installation and repairs quick, especially in high-pressure hydraulic systems where downtime is costly.

Additional reading:
Knife Gate Valves Resources | The Valve Company

Contact us to discuss your requirements of All Flanged Cross. Our experienced sales team can help you identify the options that best suit your needs.

Types of Split Flange Fittings

Different split flanges are made for different jobs. Some are designed for quick fixes, while others provide a clean finish

Split Repair Flange

This one clamps over damaged sections of a pipe. It seals off cracks or worn-out areas without needing to replace the entire pipe.

Split Flange Escutcheon Plate

Used in plumbing and HVAC systems, it covers the hole where a pipe passes through a surface. It helps block dust and moisture while making the installation look clean.

Components of a Split Flange Fitting

Every split flange fitting has key parts that work together to create a secure connection:

How Split Flange Fittings Work

A split flange grips the pipe with two separate halves that bolt together.

An O-ring sits in a groove on the flange face, sealing against leaks when tightened.

The bolts compress the O-ring against a flat surface, preventing fluid from escaping.

This setup eliminates the need for large wrenches or excessive force during assembly.

When to Use a Split Flange Fitting

Not every connection needs a split flange for pipe, but in certain cases, it’s the best option.

• Frequent maintenance areas – If a section of piping needs regular inspection or replacement, a split flange makes access easier.
• High-pressure systems – Hydraulic lines and industrial piping benefit from a secure seal that can handle intense pressure.
• Hard-to-reach installations – In tight spaces where large wrenches can’t be used, split flanges provide a practical solution.

Installation Considerations

Proper installation demands clean, smooth mating surfaces where even the smallest scratch can compromise the seal.

Workers must apply equal torque to all mounting bolts using a cross-pattern sequence, avoiding air tools that might cause over-tightening.

The flange shoulder should protrude exactly 0.010 to 0.030 inches beyond the clamp face for optimal sealing performance.

Pressure Ratings

Split flange adapters can convert Code 61 or Code 62 flange ports to JIC or O-Ring Face Seal connections, providing flexibility in system design and maintenance.

Conclusion

A split flange system provides a reliable solution for your high-pressure connections, combining simple maintenance with robust performance.

Quality split flanges, available in various pressure ratings and materials at longanflange.com, fit seamlessly into your hydraulic system design.

When you need secure, serviceable connections that last, split flange fittings deliver exactly what you’re looking for.

If you want to learn more, please visit our website All Flanged Tee.

Reference