In the HVAC industry, bearings are a critical component for transferring power from the motor to the fan impeller for belt driven fans. In this module, we will review important aspects of bearings, specifically related to the air handling applications. We will cover bearing types, housing and mounting systems, locking types, air quality handling design, basic rating life and maintenance.
What is a fan?
A fan is a rotating device that moves air. The more air volume and air pressure a fan produces, the heavier the components need to be to transmit power. Bearings are critical components that allow the fan wheels and props to rotate.
Common bearing types
The three most bearing types used in the HVAC market are: ball bearings, spherical roller bearings and tapered roller bearings. All fans from light duty to commercial and high speed industrial have different fan bearing requirements. Manufacturers are the most qualified to match the bearing selection with the required application because they work closely with the bearing manufacturer to ensure the bearing meets the product specification criteria.
Housing and mounting systems
Bearings used in the HVAC industry are mounted bearing cartridges housed in stamped steel, a cast iron pillow block, cast iron split pillow block or a cast iron flange.
The bearing housings mount the bearings to the structure. It also protects the interior bearing components and keeps them clean. Both the stamped steel and cast iron pillow block designs are the simplest housing to hold the bearing and shaft parallel to the mounting surface.
A stamped steel housing is best suited for lower horsepower and light loads. One design characteristic of stamped steel housing is the rubber sleeves round the bearing insert which secures the bearing and provides some amount of isolation between the bearing cartridge and housing components. The use of these bearings is limited to motors with one horsepower or smaller or fans with shaft diameters of one inch or less.
When fan operation levels exceed stamped steel capability, more robust bearings are required. A cast iron housing like the pillow block is used when greater horsepower and heavier loads are needed. For even higher loads, a split pillow block housing is often the choice. It has large bearings and greater lubricant capacity. The cast iron flange housing is a mounting option for a bearing cartridge. It is often the easiest to install where there is limited space in the drive chamber in the inline style fan.