Summary

Flange mount bearing

Roller bearing with set screw

Ball bearing with set

screw

Split housing

Greenheck Product Application Guide

used on Greenheck’s extended pressure CUBE exhaust fans (Model Cube-XP).

The balance of the fan and ventilator products that exceed the limitations of the

stamped steel bearings use the air handling ball bearing with the set screw locking method. This includes fans with a shaft diameter of one inch and larger, and a motor of 1 1⁄2 horsepower and larger. In applications with lower speeds the D-Lok mechanism is available, however, the D-Lok advantages are negligible and not cost justified.

When the application load and speed exceed the capacity of ball bearings, roller pillow block bearings are typically

specified. Like ball bearings, roller bearings can carry a combination of radial and thrust loads; however, roller bearings, in order to operate properly, require a radial load at least equal to the thrust load. Insufficient

radial loading allows the rollers to skid within the race, which could cause premature failure of the bearing components. Tapered roller bearings that are similar to the spherical rollers, are commonly specified for vertical applications where high thrust loads are encountered.

Currently, roller bearings are available with either the standard set screw-locking method, or the Dodge Imperial patented adapter-mounting system (spherical roller bearings only).

Thus far all of the bearing options we have discussed have been in a solid housing, either stamped or pillow block. Once the application exceeds the speed limit for the contact seal and grease sump design of the solid housing, a split pillow block bearing is typically specified. The split pillow block design incorporates a friction-free labyrinth seal and a larger grease cavity. Higher speeds can then be attained and the rollers become the limiting factor instead of the seal.

Split pillow block housings incorporate a tapered

adapter sleeve-mount locking system. Because of the geometry of the sleeve-mount design, a larger bearing is required for the same shaft size as would be used in a solid pillow block design. Consequently, the capacity of the rollers increases, thus

requiring a higher minimal radial load for proper operation of the rollers.

In some applications where contaminants need to be kept out of the bearing, special seals other than the labyrinth-type are used in the split pillow block housing. In these cases, the seal may be a speed- limiting factor and must be accounted for in the selection of the bearing.

In certain products, such as some vane axial belt drive fans, the installation of a pillow block bearing can be difficult simply because of physical space constraints within the belt

tube. In such a case, a flange- mount bearing can be used. The bearing components are essentially the same as the pillow block version, but the housing allows for face mounting around the shaft instead of pedestal mounting under the shaft.

The information in this article is a guideline to help communicate a better overall understanding of bearings and good bearing application.

Don’t let your air handling equipment suffer a short life span because of premature bearing failure. Applications are often times unique, and your selection will be based upon the bearing options best suited to your job specifications.

Greenheck engineers have over 40 years of experience in bearing selection and work closely with our vendors to ensure customers receive the highest quality products. Determine what bearing life your application requires and let Greenheck’s experienced engineering team specify the right bearing for the job.

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	Fan Application No. FA/103-00