Cleanroom HVAC and Air Handling Equipment

Backward-Curved Centrifugal Fan

A scroll-housed centrifugal fan that uses a backward-curved wheel to move clean or lightly contaminated air efficiently against the resistance of filters, coils and long duct systems.

Stable Backward-Curved Wheel
Non-Overloading Power Characteristic
Rigid Welded Scroll Casing
Adjustable Belt-Drive Base

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Product Introduction

The backward-curved centrifugal fan draws air axially through a streamlined inlet cone, turns it through the rotating wheel and converts velocity into static pressure inside a spiral casing. Backward-inclined blades provide a broad stable operating region and reduce the risk of motor overload when system resistance changes. The fan assembly combines a fabricated steel scroll, dynamically balanced wheel, external bearings, motor slide base and vibration-isolated frame for service in cleanroom HVAC plant areas.

Key Features

Backward-curved blades limit power rise beyond the selected duty point and suit variable-air-volume operation.

A close-clearance inlet cone guides air into the wheel eye with reduced turbulence and entrance loss.

External pillow-block bearings and a guarded belt drive remain accessible without entering the fan casing.

A welded structural base preserves shaft alignment while allowing the motor position to be adjusted for belt tension.

Customer Product Concerns

Central HVAC systems need a fan that can maintain useful pressure as filters load and dampers move, without exposing the motor to an uncontrolled power increase.

A forward-curved blower can draw excessive power when the actual duct resistance is lower than calculated.The backward-curved wheel has a non-overloading power characteristic that helps keep motor demand within the selected range.

Airflow falls as cleanroom filters accumulate dust and add static resistance.Variable-speed or adjustable-pulley control changes wheel speed so the fan can recover the required system pressure.

Poor inlet alignment creates uneven loading, noise and premature bearing wear.A formed inlet cone, rigid bearing pedestal and balanced wheel maintain a smooth centered flow path through the wheel eye.

Replacing belts or lubricating bearings requires opening contaminated ductwork on some fan designs.The bearings, motor and guarded drive are positioned outside the scroll for plant-side inspection and maintenance.

Typical Applications

Cleanroom air-handling unit supply and return systemsHigh-resistance final-filter ventilation branchesPharmaceutical process-area make-up airLaboratory general exhaust and air transferIndustrial clean-air drying and cooling systems

Technical Parameters

Representative construction ranges for a belt-driven backward-curved centrifugal fan used in clean HVAC service are listed below.

Core Material	Fabricated galvanized or epoxy-coated carbon-steel scroll with a welded backward-curved steel wheel and structural base
Panel Thickness	2.0-4.0 mm typical scroll side-plate and wrap thickness
Effective Width	700-2600 mm nominal fan assembly width according to wheel size
Maximum Length	Up to 4500 mm overall length including motor slide base and drive guard
Steel Facing Thickness	2.0-5.0 mm carbon-steel casing, inlet cone and reinforcement sheet
Core Density	Approximately 7800-7900 kg/m³ for the carbon-steel wheel and casing
Thermal Conductivity	Approximately 45-55 W/(m·K) for carbon-steel structural components
Surface Finish	Zinc-rich primer with blue epoxy topcoat on the base and corrosion-resistant coating on exposed steel
Joint Type	Welded spiral scroll with bolted inlet and discharge flanges, keyed shaft and belt-driven motor connection
Customization	Available based on the intended application and operating environment.

Available Options

Direct-coupled or belt-driven shaft arrangementVariable-frequency drive and duct-pressure controlSpark-resistant aluminum inlet and wheel componentsDrain connection, access door and vibration-isolation package

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