Opposed multi-blade airflow control damper: a detailed guide

Manual opposed-multi-blade damper | manual control damper | airflow control damper | control damper.

In air-conditioning and ventilation ducts, fit this product to set airflow by the blade angle. The manual opposed (single) multi-leaf damper fits square or rectangular ducts. A four-bar linkage from the handle sets the angle of the opposed multi-leaf blades, which improves control.

The airflow control damper fits air-conditioning and ventilation ducts and sets airflow by the blade closure angle. The four-bar linkage from the handle moves the opposed multi-leaf blades. The blades lock at any point in their range, and the wheel turns smoothly for easy adjustment. Manual opposed (single) multi-leaf dampers are made to the listed sizes; non-standard sizes are made to order. Large sizes use a multi-cell inner chamber. The damper fits square or rectangular ducts.

Opposed multi-leaf damper specification table (mm)

Product features:

1. The duct connection size of this damper matches the rectangular duct sizes set by the national ventilation duct standard.

2. The damper blades are opposed. In ventilation, air-conditioning and air-purification systems it works as a control damper and is better than a parallel (unison) blade type.

3. The tight opposed-multi-blade damper works both as control and as a shut-off damper, for systems that need shut-off. Examples: fresh-air and exhaust valves on air-conditioning systems, and primary and secondary return-air valves where both sealing and control are needed.

4. Tests show good air tightness, with relative leakage around 5%, and good control performance.

Scope of application:

Usually fitted on ducts of central air-conditioning ventilation systems, normally open. On a fire, when the duct gas reaches 70°C or 280°C, the damper closes automatically and within a set time meets the fire-resistance stability and integrity requirements, blocking smoke and fire. Various stainless-steel air outlets and ceiling air-conditioning nozzles.

Product classification:

The damper comes in manual and motorised types, and by seal level in tight and standard types. The motorised type adjusts airflow automatically with the control system.

The damper is made of galvanised sheet.

Traditional galvanised dampers join the four corners by welding. The heat of welding melts the zinc layer on the sheet, spoiling the look; some use large angle brackets, which cost more.

In traditional cold-rolled and galvanised dampers, the blade ends use brass bushings, some with none. The friction of the blade shaft against the frame is then high; in a large damper the resistance rises further with divided cells. Without bushings, shaft and frame wear grows, play increases over time and blade sealing drops.

In traditional cold-rolled and galvanised dampers, blades generally have no seal between them; they overlap, leaving high leakage.

In traditional cold-rolled and galvanised dampers, blade ends and the frame also have no seal.

For these reasons our engineers developed a welded-free galvanised tight airflow control damper. Its main features:

1. Galvanised sheet frame, no welding at joints, neat appearance.

2. Blades use a composite build, like tight aluminium-alloy blades. Blade ends ride on bearings, so turning resistance is very low — about one third of a traditional damper.

3. Felt strip seals between blades and between blade and frame give good sealing.

4. Gear drive gives lower resistance than the traditional linkage.

5. This damper beats the aluminium-alloy tight damper: above 1.2 m the aluminium type must divide cells because its gears at both ends have play; 0.5 mm of play across many cells leaves the farthest blade unsealed, opening a gap. Our galvanised damper uses one continuous shaft through the blades, so the blade and shaft move as one and avoid this.

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