Round Concentric Duct Reducer with Seal

A round galvanized steel concentric duct reducer (also widely known as a straight ventilation reducer or non-offset duct adapter) is a vital routing component engineered to establish a smooth, inline transition between two air ducts of different diameters. It allows installers to systematically alter the cross-section of a ventilation mainline across various installation zones while maintaining a stable air stream velocity and minimizing localized static pressure drops. This series features a fully coaxial, concentric geometry where the center points of both diameters lie on a perfectly straight line without any axial offset, making it ideal for standard linear runs within air distribution networks.

For small and medium-sized networks, these reducers are manufactured using an advanced deep-drawing automated pressing technique. This fabrication method yields an ideal, aerodynamically optimized funnel-shaped body entirely free of transverse seams, which guarantees exceptional mechanical strength and extends the operational lifespan of the entire ventilation infrastructure in residential, commercial, and industrial buildings.

Key Benefits of the Round Concentric Reducer

• High aerodynamic efficiency without airflow turbulence: The smooth funnel profile of the pressed concentric body allows air to pass freely without generating localized air vortexes or turbulent zones. This drastically lowers operational noise within the ductwork and reduces static load on the ventilation fans, saving power.
• Airtight joint isolation without messy liquid mastics: Equipped with a built-in double-lipped EPDM rubber gasket, the component creates a dense contour seal against the inner walls of the connecting ducts. This setup achieves the highest industry rating — Airtightness Class D without requiring extra sealing tapes.
• Safe on-site handling and reinforced collar stiffness: The connection rims are fully processed using machine-turned SAFE edge technology (up to D-400). The rounded borders completely eliminate sharp metal burrs to protect installers from hand cuts while substantially increasing the radial rigidity of both connection collars.
• Streamlined double male profile configuration: Both connection sides are calibrated as male fittings that slide directly inside standard straight round ducts, accelerating installation and ensuring a flush, professional fit across the network.

Technical Specifications and Installation Guidelines

• Base Material: DX51D grade structural galvanized steel
• Zinc Coating Layer: Z275 (275 g/m²)
• Metal Thickness: 0.5 mm to 0.9 mm (calibrated based on nominal collar diameters)
• Connection Profile: Double Male (both ends insert directly into straight ducts)
• Reduction Type: Concentric (coaxial alignment, zero offset)
• Reduction Angle: 45-degree smooth concentric slope for optimized flow transition
• Quality Standard: Full compliance with EN 1506:2007

Engineering Dimension Parameters

According to the technical drawing, each reducer is calibrated using precise geometric variables to ensure complete system cross-compatibility:

• Minor Nominal Diameter (Ød1): Sized with a male clearance tolerance to fit into the smaller duct run.
• Major Nominal Diameter (ØD2): Sized with a male clearance tolerance to fit into the larger duct mainline.
• Minor Collar Height (H) and Major Collar Height (L2): Precision insertion depths that ensure a stable mechanical overlap inside the pipes.
• Total Structural Length (L): Optimized layout length incorporating a smooth 45-degree transition slope to keep aerodynamic resistance at a minimum.

Assembly and Jointing Recommendations

The installation follows standard practices for male-profile ventilation fittings. The reducer inserts directly inside straight round ventilation ducts of corresponding diameters. Mechanically fix the overlapping joint node using standard blind rivets or self-tapping sheet metal screws.

If your project layout requires connecting the reducer directly to another fitting, such as an elbow or a tee, remember that a female sleeve coupling (duct coupler) must be used to link them. For non-sealed versions, always treat the joint line with specialized HVAC sealant and wrap the exterior with self-adhesive aluminum duct tape to eliminate potential air leakage.