Duct joints: the key link that connects the ventilation system

Jul 21, 2025

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Types and methods of use of air duct joints

Flange connection

Angle iron flange connection:

The most traditional way, the flange made of angle iron is installed by riveting at both ends of each section of the air duct and flanged, with a sealing gasket in the middle, and then connected with bolts. The advantages of large-size air ducts suitable for high-pressure systems are high strength, not easy to deform, easy to disassemble and connect with equipment; The disadvantages are high cost, time-consuming, large self-weight of the air duct, and difficulty in insulation at the connection.

Common Plate Flange Connection (TDF):

Suitable for rectangular ducts with a side length between 300 - 2000mm. The self-formed flange is directly rolled on the air duct through the common plate cannon combination machine, which simplifies the traditional process and improves the strength and sealing of the air duct. The process includes duct bite processing, flange surface rolling, flange corner code installation, sealant filling, and flange combination.

Combined flange connection:

The thin steel plate flange is made into a flange form with a special combined flange mechanism, which is inserted into the end of the made air duct wall after blanking, and then riveted (pressed) to connect as one. The connection between the air ducts adopts spring clip type, plug-in type or top wire snap fastening. It is suitable for metal rectangular air ducts with a working pressure of no more than 1500Pa and a long side size of the air duct not more than 2000mm.

info-1200-800

Cannot be connected

Cutting connection:

Engage with the air duct flange and reinforce the connection with the made cuttings. It is quick to install, simple to make, and has good sealing, but due to its structure, it is generally used for small air ducts in medium and low pressure systems.

Plug-in connection:

Suitable for rectangular duct straight pipe section connection, using a combination of C-side and S-side to improve connection strength and tightness. Pay attention to the order when assembling, and reserve an appropriate amount of air duct blanking

The maintenance points of air duct joints

Regular inspection:

Check whether the duct joints are loose, damaged, deformed, etc. If the bolt is found to be loose, tighten it in time; If damaged, new joint parts need to be replaced.

Cleaning and maintenance:

Regularly clean the joints to prevent the accumulation of dust, oil, etc. from affecting the sealing performance. For joints that have been used for a long time and have a lot of oil stains, they can be wiped with a neutral detergent.

Sealing treatment:

Check whether the gasket is aging or damaged, and replace it in time if there is a problem. During use, if there is air leakage at the joint, sealant can be applied to repair it.

Avoid external damage:

During daily use and maintenance of the ventilation system, it is necessary to avoid applying excessive external force to the air duct joint to prevent it from deforming or damaging. For example, when handling the air duct, pay attention to handling it with care to avoid colliding with the joint.