In rolling bearings, dust protection plays a critical role in determining service life and maintenance efficiency. Bearings on the market are generally classified into two types: open and sealed. These differ significantly in terms of application environment, maintenance requirements, and protective performance. This article provides an in-depth comparison to help you choose the right bearing type based on your working conditions.
What Are Open Bearings?
Open bearings refer to bearings without any seal or dust cover on either side. The internal components—balls, raceways, and cages—are fully exposed.
Key Features:
Simple structure with low friction
Ideal for high-speed, high-precision applications
Easy to clean and re-lubricate
Sensitive to contaminants like dust and moisture; requires a clean environment
What Are Sealed Bearings?
Sealed bearings have protective seals on one or both sides of the bearing. The most common types of seals include:
Seal Type | Code | Material & Function |
Metal Shield | Z / ZZ | Non-contact seal; blocks larger dust particles; suitable for medium-speed use |
Rubber Seal Ring | RS / 2RS | Light-contact seal with inner ring; provides better dust, water, and oil protection |
"Z" and "RS" indicate single-sided seals, while "ZZ" and "2RS" indicate seals on both sides.
Therefore, the term "shielded bearing" is too general; it's more accurate to specify "metal shield (ZZ)" or "rubber seal (2RS)".
Key Features:
Pre-filled with grease from the factory; low or zero maintenance
Excellent dust, water, and oil resistance
Slightly higher friction than open bearings; not suitable for ultra-high-speed environments
Open vs. Sealed Bearings: How to Choose
Protection: Open bearings lack sealing and rely on external dust protection; sealed bearings have built-in shields that offer superior dust and water resistance.
Friction: Open bearings offer lower friction, ideal for high-speed use; sealed bearings have slightly higher friction due to contact or near-contact seals.
Maintenance: Open types require regular cleaning and re-lubrication; sealed types are maintenance-free or require minimal service.
Ease of Installation: Open bearings need to be greased during installation; sealed bearings are ready to use, making them suitable for automated or large-scale assembly.
Application Environment: Open bearings perform best in clean, dry, high-speed settings; sealed bearings excel in dusty, wet, or frequently cycled environments.
Final Recommendation
If your equipment operates in a clean and dry environment and regular maintenance is possible, open bearings are a suitable and economical choice.
If your application involves limited space, poor sealing conditions, or exposure to dust and moisture, it’s best to choose sealed bearings—either with metal shields (ZZ) or rubber seals (2RS)—for greater durability and longer service life.
For expert guidance or customized solutions for bearings, please contact us at info@chg-bearing.com. CHG is your trusted partner for precision bearings built to meet the most stringent industrial demands.
