Contamination Risk
Sealed or shielded bearings are often selected where dust, dirt or moisture protection is important, depending on the application.
BMG World Bearing Support
Sealed vs Open Bearings
Sealed and open bearings can suit different machine positions. The right choice depends on contamination risk, lubrication access, speed, heat, load, shaft and housing design, operating environment and the full bearing suffix shown on the removed part.
Lubrication Access
Open bearings may be selected where the machine design allows inspection, lubrication control or relubrication through the bearing position.
Suffix Matters
Codes such as ZZ, 2RS or similar suffixes can change the bearing variant. Always confirm the full listing before ordering.
Bearing Selection Guide
How to compare sealed and open bearings before ordering
Sealed, shielded and open bearings are selected for different maintenance and operating conditions. The best choice depends on how the bearing is lubricated, how exposed it is to contamination, and whether the machine design requires a specific closure type.
What is the difference between sealed and open bearings?
A sealed bearing has an integrated closure designed to help keep lubricant inside and reduce the entry of contaminants, depending on the seal design and operating conditions. An open bearing does not have an integral seal or shield, so it may be selected where the machine design provides lubrication, protection or inspection access. A shielded bearing sits between these options in many product ranges, but the exact meaning must be confirmed from the product listing.
Sealed bearings Often selected where contamination protection and retained grease are important, depending on speed, temperature, seal design and application conditions.
Open bearings Often selected where the machine design allows lubrication, inspection or where the bearing position already has external sealing or lubrication control.
Shielded bearings Commonly used as a closure option where a shield helps reduce contamination entry while not being the same as a contact seal. Confirm the suffix before ordering.
1. Contamination protection
Sealed or shielded bearings are commonly considered where dust, dirt, moisture or handling contamination are concerns. Protection still depends on the actual closure design and environment.
2. Lubrication access
Open bearings may suit positions where the machine provides lubrication access, inspection or a specific lubrication system. Check the machine requirements before changing bearing type.
3. Speed, heat and friction
Closure type can affect running behaviour. Confirm the product listing, speed guidance, lubrication method and operating temperature before selecting a sealed, shielded or open variant.
When should you use a sealed bearing?
A sealed bearing is often selected where the bearing position is exposed to dust, dirt, moisture, handling contamination or limited maintenance access. Sealed options can be useful in workshops, agricultural equipment, general manufacturing and other environments where cleaner internal running is important, but they are not automatically the correct choice for every machine.
Dust or dirt exposure
Sealed bearings are commonly considered where fine dust, dirt or workshop debris could enter the bearing. Confirm the seal type and application before ordering.
Moisture risk
Where moisture is present, sealing may help reduce ingress depending on the design and conditions. Do not assume every sealed bearing is suitable for washdown or wet service.
Limited relubrication access
Sealed variants may be selected where routine relubrication is not practical, but the correct bearing still depends on load, speed, heat and machine design.
Like-for-like replacement
If the removed bearing has a seal suffix, match the full code, suffix and dimensions where possible, then check the live product details before ordering.
When should you use an open bearing?
An open bearing may be selected where the equipment design provides separate sealing, oil or grease lubrication, regular inspection access or a specific lubrication arrangement. Open bearings can be suitable in many industrial positions, provided the surrounding machine design protects and lubricates the bearing correctly.
External lubrication system
Open bearings may suit positions where the machine supplies oil or grease through a housing, gearbox, lubrication line or other designed lubrication route.
Inspection or maintenance access
Where the bearing position is regularly inspected or serviced, an open bearing may be part of the original maintenance design.
Machine has its own sealing
If the housing, cover or separate seal already protects the bearing, an open bearing may be specified by the equipment design.
Original specification requires it
If the removed bearing was open, do not change to sealed or shielded without checking speed, heat, lubrication path, clearance and machine requirements.
What do ZZ, 2RS and shielded bearing mean?
Bearing suffixes help identify the variant, but they are not universal across every manufacturer or bearing type. Codes such as ZZ, 2Z, RS, 2RS or similar markings are common examples linked to shields or seals in many listings. Always confirm the exact suffix shown on the removed bearing, packaging or live product listing before ordering.
ZZ, Z or 2Z
Often used to indicate metal shields, depending on the manufacturer and bearing type. Check whether the bearing is shielded on one or both sides.
RS, 2RS or similar
Often used to indicate rubber seals or contact seals, depending on the brand. Match the removed bearing where possible and confirm the listing.
Open bearing
An open variant normally has no integral seal or shield. Confirm that the machine provides the required lubrication and protection before ordering.
Other suffixes
Other letters may relate to clearance, cage, snap ring grooves, materials, lubrication or special designs. Do not ignore extra letters in the bearing code.
Environment-based selection checklist
Use the operating environment as one part of the decision. Dust, moisture, heat, speed and lubrication access can all affect whether a sealed, shielded or open bearing is suitable.
Dust and dirt Check whether the position is exposed to cement dust, soil, workshop debris, metal particles, agricultural dust or mining contamination.
Moisture and washdown Confirm whether water, humidity, cleaning liquid, washdown or outdoor exposure could affect the bearing, housing or lubricant.
Heat and speed Review operating temperature and speed. Closure type, lubricant and bearing design can all influence running behaviour.
Lubrication method Check whether the machine relies on pre-greased bearings, relubrication points, oil lubrication, grease lines or a separate maintenance schedule.
Shaft and housing Confirm bore, outside diameter, width, housing condition, shaft condition, fit, alignment and any separate seals or covers.
Existing bearing suffix Match the suffix from the removed bearing where possible. If it is unreadable, capture measurements, photos and the machine position before ordering.
Can you replace an open bearing with a sealed bearing?
Do not change from open to sealed, sealed to open, or shielded to sealed by size alone. Even where the bearing dimensions look the same, the closure type can affect lubrication access, heat, friction, speed suitability, contamination control and the way the bearing works inside the machine. A like-for-like suffix match is usually safer unless the machine requirements have been checked.
What to check before ordering a replacement bearing
Before placing the order, record the full bearing number, suffix and application conditions. This helps reduce the risk of choosing the right size but the wrong closure type.
Full bearing code Capture the complete code, including suffixes, hyphens, spaces, brand marks and any clearance markings shown on the removed bearing.
Closure type Confirm whether the removed bearing is open, sealed, shielded, sealed on one side, shielded on one side or part of a special assembly.
Dimensions Check bore, outside diameter and width if the marking is incomplete or if the product listing needs confirmation.
Operating conditions Record load direction, speed, temperature, contamination exposure, moisture exposure, lubrication method and whether the position has failed before.
Frequently asked questions
What is the difference between sealed and open bearings?
Sealed bearings include an integrated closure to help retain lubricant and reduce contaminant entry, depending on the design. Open bearings do not have an integral seal or shield and may be used where the machine provides lubrication, protection or inspection access.
When should I use a sealed bearing?
A sealed bearing is often selected where contamination protection, retained grease or limited maintenance access are important. Check the exact suffix, speed, heat, load, lubrication and application conditions before ordering.
When should I use an open bearing?
An open bearing may be suitable where the machine design provides external lubrication, separate sealing or regular inspection access. Do not assume an open bearing is unsuitable simply because the environment is dusty; check the whole bearing position.
Are sealed bearings better for dusty conditions?
Sealed bearings are commonly considered where dust or dirt could enter the bearing, but they are not always better in every application. Speed, heat, lubrication, seal design and machine requirements must still be checked.
Can open bearings be relubricated more easily?
Open bearings may allow easier lubrication access where the machine is designed for it. The correct answer depends on the housing, lubrication system, maintenance schedule and whether the bearing position has separate seals or covers.
What does ZZ, 2RS or shielded bearing mean?
ZZ, 2Z, RS and 2RS are common suffix examples used in many bearing listings to describe shielded or sealed variants. Meanings can differ by manufacturer and bearing type, so confirm the actual product listing before ordering.
Can I replace an open bearing with a sealed bearing?
Not without checking the machine requirements. A sealed bearing may affect lubrication access, heat, friction, speed suitability or fit in the bearing position. Match the old suffix where possible and confirm before ordering.
What should I check before ordering a replacement bearing?
Check the full bearing number, suffix, seal or shield type, clearance, dimensions, load, speed, shaft and housing design, lubrication method and operating environment.
How do dust, moisture, heat, speed and lubrication affect bearing choice?
Dust and moisture can increase the need for protection, while heat, speed and lubrication method can affect whether a sealed, shielded or open bearing is suitable. Use the application conditions together, not one factor alone.
Should I match the bearing suffix from the old bearing before ordering?
Yes, where possible. The suffix can identify whether the bearing is open, sealed, shielded, has a specific clearance or includes another design feature. If the suffix is unreadable, provide photos, measurements and application details.
Need to choose between sealed and open bearings?
Use the removed bearing and machine conditions as the starting point. Confirm the full bearing code, suffix, closure type, dimensions, lubrication method and operating environment before ordering a replacement.