A bearing's closure affects contamination protection, friction and relubrication. The choice between an open bearing, ZZ shields and 2RS contact seals should match the machine's actual environment.
Open bearings offer low friction in clean, externally lubricated assemblies. ZZ shields limit larger particles with little resistance. 2RS seals protect more effectively against dust and moisture but normally create more friction.
What to Focus On
- open: clean environment and external lubrication
- ZZ: higher speed and light protection
- 2RS: dust, splash water and difficult access
- single-sided closures for special assemblies
- seal compatibility with temperature and lubricant
Recommended Procedure
- Identify the sources of dirt and moisture.
- Confirm the required speed and operating temperature.
- Decide whether the bearing needs relubrication.
- Choose enough protection without unnecessary friction.
Common Mistake
A stronger seal is not automatically better. In a clean high-speed arrangement it may raise temperature and energy consumption without adding value.
Summary
The right closure balances protection, speed, temperature and maintenance needs.