Circular Non-Return Valve

A circular galvanized steel non-return valve (butterfly-type backdraft damper) is an automatic safety device engineered to prevent the reverse migration of air masses and eliminate backdrafts within climate networks. This inline shutter component isolates the duct run completely, solving the critical issue of external air infiltration the exact moment the forced extract or supply fan stops operating. By physically sealing the pipe cross-section, it effectively bars cold drafts, unconditioned humidity, ambient outdoor smells from shared shafts, street noise, and insects from entering residential rooms, bathrooms, kitchens, and office layouts, thereby maintaining a stable and protected internal microclimate.

The valve housing sleeve and symmetric folding blades are manufactured on automated assembly lines from high-grade structural galvanized sheet steel, grade DX51D, carrying a stable protective hot-dip zinc coating mass of Z275 (275 g/m²). The rigid mechanism is designed for continuous, long-term service and resists moisture corrosion present in warm exhaust air paths. The butterfly flaps are secured onto a heavy-duty central steel axle and equipped with lightweight return springs that ensure immediate, autonomous closure as soon as static network pressure drops to zero.

Key Benefits of the RSK Non-Return Valve

• Fully autonomous operation with zero power consumption: The butterfly mechanism functions solely under the kinetic pressure generated by the active fan airflow. The blades glide open smoothly when the system starts and snap shut via the integrated torsion springs upon fan shutdown, eliminating the need for electric control cables and cutting down equipment budgets.
• Acoustic comfort with cushioned anti-slam dampening: The internal blade stop tabs are fitted with soft, shock-absorbing dampening elements that suppress impact noise. This effectively eliminates loud metallic clicking or rattling sounds during sudden network pressure fluctuations or heavy outdoor wind gusts.
• Rigid inline positioning with zero shifting risk: The casing is structured with a calibrated male profile for direct sliding inside straight circular pipes. A prominent pre-rolled 10 mm center stop bead serves as a physical insertion barrier, locking the exact seating depth of the valve and preventing it from migrating down the duct track under high-velocity streams.
• Exceptional structural lifespan in humid conditions: The structural combination of a DX51D galvanized body shell and optimized spring calibrations guarantees mechanical reliability across years of exposure to changing air currents and moisture, ensuring zero structural sagging or blade friction jams.

Technical Specifications and Dimension Data

The linear variables, mounting tolerances, and nominal diameter calibrations of our circular backdraft dampers fully comply with European standards EN 1505:2000 and EN 1506:2007 for sheet metal ventilation air tracks. The internal spring load assembly is factory-calibrated to match standard duct system velocities.

• Casing Base Material: High-quality hot-dip galvanized sheet steel DX51D (Z275 passivation)
• Shutter Blade Material: Lightweight sheet steel or aluminum optimized for low-pressure opening
• Return Mechanism Type: Integrated heavy-cycle torsion wire spring
• Connection Interface Type: Double male nipple profile calibrated for inline sliding inside duct runs