Non-Return Damper

1. Overview of Check Damper (Non‑return Damper)

1.1

Check damper is special duct fitting for ventilation systems, which opens and closes automatically by air flow and gravity to prevent reverse air‑flow back‑flow. When fan runs, airflow pushes blades to open damper. After fan stops, blades close automatically by gravity to block reverse airflow. Available in rectangular and round sizes, suitable for horizontal and vertical duct installation.

‑ Gravity Check Damper: Operates purely by gravity without power supply, simple structure for general ventilation ducts. ‑ Gravity‑louvre Check Damper (Self‑closing Louver Damper): Self‑dropping louver blades, widely used for fan outlet and wall‑mount fan discharge side. ‑ Tight‑seal Check Damper: Equipped with sealing gaskets for better shut‑off tightness, for waste‑gas and exhaust systems.

1.2 Product Classification

‑ By structural shape: Rectangular type, Round type. ‑ By functional configuration: ‑ Gravity Type: Auto open‑close by gravity, no sealing gasket, for general ventilation. ‑ Self‑dropping Louver Type: Louver‑blade structure, applied for fan outlets. ‑ Tight‑seal Type: With sealing gasket for high closing tightness.

2. Operating Conditions for Check Damper

Operating temperature: ‑20 ℃ ~ +80 ℃ Relative humidity: less than 90% Medium condition: General ventilation air; anti‑corrosion version for dust‑free corrosive gas.

Power supply: No power required.

3. Check Damper Configuration

3.1 Standard Components

‑ Damper body ‑ Blade assembly ‑ Rotating shaft ‑ Connecting flange

3.2 Optional Accessories (please specify requirements upon order)

‑ Sealing gasket ‑ Anti‑corrosion coating ‑ FRP anti‑corrosion damper body

4. Manufacturing Process of Check Damper

4.1

Damper body and blades are fabricated from galvanized steel sheet. Counter‑weight fitted on blades to ensure sensitive gravity‑driven operation. Rotating shaft equipped with wear‑resistant bushing for smooth non‑jamming movement. Anti‑corrosion models adopt anti‑corrosion coating or FRP material for body and blades.

4.2

Damper flange is integrally bent to form flat mating surface for easy duct connection.