Rectangular Air Volume Control Damper

DeFa rectangular air volume control dampers are used to regulate airflow in square and rectangular duct systems. The product line covers both manual and motorized versions, with standard sizes ranging from 100×100 mm to 1000×1000 mm. Custom dimensions, flange types, and surface finishes can be supplied based on project requirements. These dampers are manufactured by Shengyuan Technology under the DeFa brand, a company with over 20 years of experience in environmental control equipment and high voltage power systems.

The dampers are suitable for air balancing, zone control, and airflow adjustment in HVAC systems, cleanrooms, and industrial ventilation. Material options include carbon steel, 201 stainless steel, 304 stainless steel, and 316 stainless steel, allowing the product to match different installation environments and corrosion resistance needs.

General Specifications

Standard Size Availability

The following table lists commonly stocked rectangular dimensions. Other sizes can be produced on request. Dimensions are expressed as width × height in millimeters.

Note: The above list reflects typical production capability. For dimensions not listed, please contact our technical team with the required width and height. Large sizes may require reinforced blades and higher torque actuators.

Material Selection

• Carbon steel: Economical option for general indoor ventilation. Galvanized or powder-coated finish provides basic corrosion protection.
• 201 stainless steel: Suitable for mild corrosive environments, such as kitchens or general industrial exhaust with moderate humidity.
• 304 stainless steel: Recommended for humid, coastal, or food processing environments where good corrosion resistance is needed.
• 316 stainless steel: Used in chemical fume exhaust, laboratory ventilation, and marine applications where resistance to chlorides and aggressive chemicals is required.

Control Options

Manual Dampers

Manual versions are fitted with a locking quadrant handle or a hand wheel. The handle position indicates blade angle and can be locked after adjustment. Manual dampers are typically used during system commissioning or where airflow changes are infrequent.

Motorized Dampers

Electric actuators are mounted directly on the damper shaft for automatic airflow control. Modulating actuators accept 0-10V or 4-20mA signals, allowing the damper to respond to building management system commands. Two-position actuators are also available for simple open and close service.

Combined Manual and Motorized

Some actuator models include a manual override function. This allows local operation during commissioning or power failure. The combined configuration is useful for maintenance and emergency adjustment.

Construction Features

• Blade design: For smaller sizes up to approximately 300×300 mm, a single blade is used. Larger sizes use multi-blade construction to reduce blade deflection and improve airflow uniformity.
• Shaft support: Self-lubricating nylon or bronze bearings reduce friction and eliminate the need for regular lubrication.
• Sealing: Blade edge seals and frame gaskets minimize air leakage in the closed position. Leakage class can be selected based on project requirements.
• Surface treatment: Carbon steel versions can be galvanized, painted, or powder coated. Stainless steel versions are supplied with natural or brushed finish.

Installation Guidance

• Install in a straight duct section. A straight run of 2 to 3 duct diameters before and after the damper ensures stable airflow and accurate control.
• For manual dampers, provide access space for handle movement and position reading.
• For motorized dampers, confirm actuator rotation direction before final electrical connection.
• Use flexible connections where duct vibration may be transmitted to the damper.
• For flanged models, tighten bolts evenly to prevent body distortion and seal leakage.

Maintenance and Inspection

• Quarterly: Check blade movement and clean dust from seals and blade edges. Verify that position indicators match actual blade angle.
• Semi-annually: Inspect bearings for wear and actuator torque. Tighten any loose fasteners.
• Annually: Perform full stroke test for motorized versions. Replace worn seals, corroded parts, or aging actuator batteries if applicable.

Frequently Asked Questions

Can I order a rectangular damper in a size not listed in the table?

Yes. Custom dimensions are available. Provide the exact width and height, plus any special requirements for flange type or material. Our engineering team will confirm feasibility and provide a quotation.

How do I decide between manual and motorized control?

Manual dampers are suitable for fixed balancing where adjustments are made only during commissioning. Motorized dampers are needed when airflow must change automatically based on sensors or a building management system. If you are unsure, we can help assess the control logic of your project.

Which material should I choose for a kitchen exhaust system?

For kitchen exhaust with high humidity and oil vapor, 304 stainless steel is normally recommended. It resists corrosion and is easy to clean. For very aggressive chemical exhaust, 316 stainless steel is the better choice.

What information is needed for a quotation?

Please provide the damper dimensions, material, control mode (manual or motorized), actuator voltage and signal type, and the required leakage class. If custom flanges are needed, include the flange standard or drawing.

Is the damper suitable for outdoor or rooftop installations?

Yes. Select a stainless steel body and an actuator with IP54 or higher protection. A weather shield over the actuator is also recommended to extend service life.

What is the typical delivery time for standard and custom sizes?

Standard sizes are often available within 7 to 15 working days. Custom sizes and special materials may take longer depending on the order quantity and current production schedule. We provide a delivery estimate with each quotation.

About Shengyuan Technology

Shengyuan Technology (DeFa brand) has been active in environmental control equipment and high voltage power systems for more than 20 years. The company's manufacturing scope includes dampers, air purification modules, and high voltage generators, serving customers in North America, Europe, and Asia. Rectangular air volume control dampers are produced under a documented quality management system, with dimensional inspection, material traceability, and actuator function tests carried out before shipment.