Bearing Life Specs Can Make or Break Fan Performance

December 20, 2018
Palani Ammasai

It’s tempting to exclude bearing life from your fan specs. Many people don’t include them. But a small oversight like this can cost you significantly in repairs and downtime down the road.

Smart contractors and engineers insist on a minimum L10 bearing life of 50,000 hours, which works out to about 5.7 years of continuous duty. If you don’t ask for that in the specs, nine times out of ten you’ll get bearings that are either junk or ones that will fail just after their 12-month warranty expires.

That’s when your pain begins.

Why bearing life matters

Replacing bearings is probably the most labor-intensive fan repair job there is. Maintenance guys dread the process because it involves taking most or all of the fan apart — not unlike a car repair that requires removing the engine.

Commercial fans typically come with bearings that are mostly aluminum or some other lightweight hybrid. As a result, they’ll lose their shape quickly in an industrial environment. Since bearings typically require specific configurations, it’s not easy to upgrade an existing fan to higher-quality bearings without a major retrofit.

High-quality industrial bearings are made from hardened steel, which is significantly more durable than aluminum. They’re also more likely to come in a packed or pressurized housing that keeps oil distributed throughout the whole bearing assembly. Oil in commercial assemblies tends to pool at the bottom due to gravity.

Commercial bearings can’t take the heat (or the cold)

The phrase “some like it hot” doesn’t apply to commercial-grade bearings, which typically can’t function well above 45 °C (113 °F). They also can’t handle environments colder than -10 °C (14 °F). Industrial fans are designed to work at much higher and lower extremes, i.e., between -40–85 °C (-40–185 °F).

When a fan can’t fail

Hardened steel ball bearings can handle about 90 percent of industrial jobs. But if you’ve got a critical fan that simply can’t be allowed to fail, consider cylindrical sleeve bearings. These cost a bit more, but tend to last two to three years longer than standard ball bearings. They allow fans to run at higher RPMs without the risk of the bearings losing their shape.

Sleeve bearings can also take much more of a beating in aggressive environments such as coal mines. Another advantage in critical environments is sleeve bearings are more likely to slow (rather than completely stall) a fan when they reach the end of their lifespan.

Don’t fall for dirty tricks in fan life ratings

For a truly direct comparison, insist on the L10 standard defined by the American Bearing Manufacturers Association (ABMA). Simply put, this is the number of hours in service that 90 percent of the bearings will survive. Some manufacturers will try to fool you by quoting an “L50” life to make their fans look more durable. (Seriously, how effective do you think a fan is well before half its bearings go bad?) Get the facts by demanding the L10 life. Better yet, run the other way from any vendor who stoops to this deceptive practice.

Ready for durable, hard-working fans that won’t need bearing replacements this time next year (or in the next five years)? Contact Hartzell Air Movement for a no-obligation consultation.