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Bearing Guide

             An axial fan consists of two main parts, the spinning impeller and its non-moving housing. They meet at the center using bearings that rotate on the shaft of the housing. Bearings are responsible for minimizing friction between the two parts. Because the bearing is such a critical component of the fan, the type chosen will result in very different characteristics for the fan. The five key distinctions between the bearings are the noise levels, life expectancy, operating conditions, available mounting positions, and the price. Please keep in mind that many of these parameters mentioned are also influenced by other factors than just bearings.

 

Bearing System
Noise Level
Life Expectency
Environment Mounting   Cost 
Sleeve  Quietest  41,000 Hours Low Heat. Higher Shocks  Horizontally   Lowest  
Ball Louder 55,000 Hours Higher Heat. No Shocks
Any    Average 
One Ball One Sleeve Loudest 67,000 Hours Low Heat. Higher Shocks
Any    Average 
Dual Ball Quieter 67,000 Hours Higher Heat. No Shocks
Any   Highest  

 

Noise Level

            

The noise level emitted by a fan depends on various factors including the fans speed, age, and bearing system. Regardless of the bearing it uses, fans with higher speeds are louder than lower speed ones. At low speeds, comparable fans produce similar noise levels. But at higher fan speeds, sleeve bearing fans are noticeably quieter and one-ball one-sleeve bearings noticeably louder. Fans are also noisier as they age regardless of speed or bearings. Because sleeve bearing fans have the shortest life expectancy, they will become louder at a faster pace than all other bearing types.

Life Expectancy

            

The life expectancy of a fan depends on numerous factors including operating temperature and bearing system. A fans lifespan becomes shorter as its surrounding temperature increases, no matter what bearings it uses. At lower temperatures, fans will have a similar lifespan. As the temperature increases, dual ball bearing fans will live considerably longer than sleeve bearing fans. The noise level which is partially dependant on the fans age will reflect this relation. Also, the improper mounting of sleeve bearing fans will decrease its life expectancy.

Operating Environment

            

Different types of bearings are suitable for operating for different environments. A fans life will decrease as the temperature of its environment increases no matter what bearing it uses. Although all fans start off with a similar lifespan at very low temperatures, sleeve bearings will have a much shorter life span than ball bearings at higher temperatures. Another point is that ball bearing fans are not suitable in environments where there is a lot of movement. They are very sensitive to shocks and are likely to sleeve bearing fan.

Mounting

             Due to its lubricant dependent construction, sleeve bearing fans should only be mounted and stored horizontally. Meaning it should always stand upright with the direction of the airflow parallel to the ground. If mounted improperly, its life will shorten and the noise level will also increase. On the other hand, Ball bearing can be mounted various positions without endangering its life span.

Cost

            

The sleeve bearing consisting of a simple sealed cylinder of lubricant is the easiest to manufacture and therefore is the cheapest. As you move towards ball bearings which are constructed with a complex ring of spherical balls with springs, the fan becomes more expensive. Sleeve bearings are very cost effective for applications that have a low temperature environment while dual ball bearings are superior if cost is not a major factor.