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Backward Curved Fan

backward-curved-fan-wheelBackward Curved Centrifugal Fans * High Operating Efficiencies * Heavy Duty Construction

The AirPro backward curved centrifugal fan (BCHS) is designed to handle high air volumes at high static pressures. Used to move mostly clean air, our BCHS fan can be used as a forced draft or induced draft fan for a wide range of industrial applications.

Whether standard or custom, AirPro BCHS fans are designed and built with unmatched quality and backed by responsive, respectable service.

Will the AirPro BCHS fan work for my application?

Whether you are considering a standard engineered BCHS fan or one that is custom built to your specifications, you need to be confident it will work for your application. We want you to be sure. Use our online selection tool, myAirPro, to specify and price a BCHS fan, or talk to one of our engineers at 715-365-FANS (3267).

Accessories and Spare Parts

When you specify or purchase BCHS fans from AirPro, be sure to consider accessories and spare parts, too. Accessories such as dampers give you greater flexibility to manage the flow of air into and through the fan. And, it is always a good idea to have spare parts on hand for each backward curved fan to help keep your operation up and running.


BCHS Fan Performance & Design

Based on performance testing according to AMCA standards, Finite Element Analysis, and years of engineering and field experience, AirPro’s BCHS fan has been developed with the following performance and design characteristics:

  • Air volumes up to 300,000cfm
  • Static pressures up to 40”wg
  • Temperatures up to 1000°F
  • High static efficiency up to 78%
  • Non-overloading power curve
  • Single Width, Single Inlet (SWSI) and Double Width, Double Inlet (DWDI)


Clean air-to-light dust loading applications that use AirPro BCHS fans include:

  • Baghouses
  • Boilers
  • Dryers
  • Forced Draft
  • Heat Exchangers
  • Induced draft
  • Pollution Control Equipment
  • Rotary Drum Dryers
  • Scrubbers
  • Thermal Oxidizers


Fan arrangements define the way a fan is driven by a motor, how the motor mounts to the fan, and are based on AMCA standards. BCHS fans are available in the following arrangements:

  • Belt-drive – The fan shaft is driven by the motor shaft through sheaves/pulleys and v-belts. Belt-driven fans provide speed and flexibility, as they enable the fan operating speed to differ from the motor synchronous speed. There are power losses associated with belt-driven fans, and that should be considered when selecting the motor horsepower.
    • Arrangement 1 – The fan and motor are separately mounted to a unitary base. OSHA guards are required.
    • Arrangement 9 – The motor mounts to the side of the fan pedestal with no unitary base required. OSHA guards are required.
  • Direct-Drive – The fan operates at the synchronous speed of the motor, as the fan is driven directly either with the fan wheel mounted on the motor shaft or with the fan shaft directly coupled to the motor shaft. Direct-driven fans do not experience power losses, as they do not involve any belts.
    • Arrangement 4 – This is a low cost arrangement, as the wheel is mounted directly on the motor shaft and does not require bearings, belts, OSHA guards, or a unitary base. This arrangement is not available for every fan, as operating temperature, wheel size, materials, and other criteria can be limiting factors.
    • Arrangement 8 – The fan shaft is directly coupled to the motor shaft with a flexible coupling. This arrangement offers fewer potential maintenance issues than other arrangements, as there is no belt pull on the bearings, and the motor experiences neither belt pull nor the weight of the wheel on its shaft. OSHA guards are required, but a unitary base is necessary only when spring vibration isolators are required.
    • Arrangement 3 and 7 – These can be either belt or direct drive, and both arrangements involve a bearing on either side of the fan wheel. The bearing is supported either by separate pedestals or by a support structure integrated with the fan housing.

Materials of Construction

We offer a wide range of materials to construct the fan wheel, airstream parts or the entire fan. Whether your application involves high operating temperatures, caustic contaminants, or explosive environments, AirPro has the appropriate materials, including:

  • All carbon steel grades
  • All stainless steels
  • Nickel-based alloys (625, C22, C276, etc.)
  • Titanium
  • Monel
  • Aluminum

BCHS Fan Finishes

We offer various finishes and linings to accommodate multiple application requirements. Our standard industrial primer and enamel will protect our fans in a general industrial environment. We also provide finishes and linings that offer protection in specialized environments, such as high temperature, corrosive, abrasive, and food-grade environments.

  • Standard 2-coat industrial enamel
  • Wet paints, including:
    • Epoxy
    • Enamel
    • Polyurethane
  • Powder coating
  • Special linings, including:
    • Rubber
    • Ceramic tile
    • Teflon
  • Other custom coatings available


Routine maintenance is essential to the successful, long-term operation of your BCHS fan. We understand that this can be a challenge due space limitations and fan accessibility. AirPro fans have several features available that are designed to facilitate routine maintenance, including:

  • Flush-mounted and gasketed access door into the fan housing
  • Split housings for wheel and shaft removal
  • Extended lubrication lines for motor and bearing ports
  • Lubrication access holes in the shaft guard
  • Tachometer access hole in the belt guard
  • Sealed exterior seams for rust prevention

Quality Control Inspection

Inspections are conducted to ensure AirPro Fans not only comply with the customer’s requirements, but that they also maintain AirPro’s high standard of quality. These inspections are conducted throughout the manufacturing process, including:

  • Material receiving and preparation
  • Fabrication and welding
  • Paint/coating and surface preparation
  • Product final assembly
  • Balance and vibration analysis
  • Final inspection before shipping with QC documentation provided

Fan Balance and Testing

Wheel balance and fan vibration levels are issues we take very seriously; ignoring them can cause catastrophic failures in the field. We conduct various tests to address these critical issues.

  • Wheel is dynamically balanced to ISO G6.3 minimum
  • Full-speed, mechanical run test is performed on the fan assembly
  • Vibration analysis conducted at fan’s operating speed
  • Vibration analysis conducted during fan coast-down to detect any resonance
  • In-depth bearing analysis designed to detect any potential bearing problems

Interested in learning more about our centrifugal fans and blowers?  Contact us and we will be happy to assist you.