When bearings don’t work up to their potential

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By Steve Katz, Action Bearing Boston
Emerson Bearing Boston
Edited by Mike Santora

iStock_000009209925LargeWhen specifying the correct bearing to use in an application, there are critical factors to take into consideration such as:
· Envelope dimensions
· Axial and Radial loads to be carried
· Speed limits
· Inch or Metric design
· Lubrication criteria
· Ambient operating temperature and more

The majority of our sales are to original equipment manufacturers (OEM) who already know what bearings they need to specify in a new design, or to Maintenance, Repair and Operations (MRO) as to what bearing came out in a repair application. The vast majority of bearings work up to their potential ‘B-10’ life. However, there are times when things do not “roll along” smoothly, and we are consulted about a new design or about how to optimize a design that is not meeting expectations.

For example, we were contacted online by a designer who was developing a new Audio Turntable which used miniature bearings with a bore size under ½’ (.500). He felt that there were issues in the performance of the components, perhaps being impacted by the bearings. We started by reviewing the running accuracy between the tone arm and the turntable. The first step was to look at the “radial runout” in an effort to decrease the amount of endplay or wobble that would affect the tracking of the tone arm. In this case, we reduced the clearance within the bearing (P5-8 to P2-5). However, there was another issue causing problems. The bearings had initially been lubricated with grease. We switched over to a high-grade oil lube, which corrected stiffness at initial rotation and the problem was resolved.

Improving the life of the bearing

Rolling paper machine

Rolling paper machine in a paper factory.

One application where we wanted to improve bearing performance was in the Metal Shredding industry. In this case, a massive rotor that is supported by very large Spherical Roller bearings (14” shafts and larger) spins and “chops up” the cars as they fall down from a large conveyor and chute. This is a severe application in terms of loads and stress on the bearings. The challenge here was to improve the life of the bearing. We made two significant changes. The first was to use a roller bearing with a different cage design separating the rollers, which better handled the large shock loads and allowed for better lubricant flow. The second change, although initially expensive, was a switch from grease to a recirculating oil system. This lowered the operating temperature of the unit by 20° Fahrenheit.
Overall, we were able to improve the life of the bearing from six months to 14 months on average.

Using high-end lubricants for improved performance

While all bearings have an expected life in terms of hours, based on load and speed conditions, it is also important to use a grease that has an equal or better “service life”. To give you another example, in a Tissue Paper mill, we had supplied a radial bearing for the winding rolls appropriate for the load and speed conditions. Yet, the bearings were failing because the grease they were using did not have the same life potential as the bearing. After switching over to a high-end Kluber lube, bearing performance and life improved immediately.

Grease, which is easy to handle and simplifies the sealing system, is the lubricant most often used, whereas oil is generally appropriate for high speed or high-temperature operations. In all of the instances above, a change in lubrication was key and should always be taken into consideration.

Emerson Bearing Boston
www.emersonbearing.com

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