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How Temperature Conditions Affect Bearing Performance

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By: Joyce Laird, Contributing Editor

Temperature conditions are extremely important for bearing performance. Adam Leese, Application Engineer for NSK says that knowing the ambient temperature of the application allows for proper selection of bearing materials such as seals, rings, rolling elements, and cage,. It also provides information for grease type, bearing internal clearance, and shaft/housing fits.

“Failure to match the bearing design to the temperature conditions can lead to catastrophic failures,” he warns. Some of these are noted below:”

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Here we see an NSK SJ design high-temperature ball bearing with solid lubricant, an example of NSK’s SPACEA Series bearings for extreme environments. SJ Bearing Applications: Vacuum vapor deposition equipment, kilns, kiln cars, steel plants, high-temperature conveyance equipment.

Potential High Temperature Issues

  • Lubricant life is reduced. In general, grease life is cut in half for every 15°C rise above 70°C.
  • Lubricant viscosity becomes too low, leading to reduced fatigue life.
  • Raceway hardness is reduced, leading to reduced fatigue life.
  • Seals dry & crack, leading to loss of lubricant, entrance of contamination.
  • Cage/retainer weakens, leading to catastrophic failure.
  • Rings experience permanent growth, leading to changes in fits, wear of shaft, inability for bearing to float in housing, loss of bearing internal clearance.

Potential Low Temperature Issues

  • Lubricant viscosity becomes too high, leading to increased torque, skidding.
  • Seals lose pliability, leading to seal failure, loss of lubricant, entrance of contamination.
  • Cage/retainer becomes brittle, leading to catastrophic failure.

“If a bearing designed for operation at normal temperatures is used in an extremely high or low temperature environment, the bearing life and performance will be unsatisfactory,” Leese says. “Fortunately, special bearing designs exist for temperature ranges as low as – 200°C for Cryogenic applications and up to 400°C for oven applications. Knowing your expected temperature in the application, along with other application information such as required loads and speeds, allows for proper bearing design/selection.”

It is important to know the working environment of the bearing assemblies at the start of any project, because experimentation in any of these cases is nota safe option. If working with a specifically hard to pinpoint design where there might be doubt as to which bearing to select, it pays to ask a bearing expert. This will save a lot of cost down the road.

“Incorporating the proper design for your specific operating temperature will maximize bearing performance,” Leese concludes.

NSK Americas
http://www.nskamericas.com