Grease for Sealed (Lubricated-for-Life) Bearings

Sealed bearings are factory-filled with a calculated quantity of grease and sealed to prevent contamination ingress and lubricant loss. These bearings are designed to operate for their calculated service life without relubrication.

Seal Types and Speed Limits

Seal Type	Designation	Speed Limit vs. Open	Characteristics
Shields	ZZ, 2Z	90-95%	Non-contact, allows some air exchange
Contact Seals	2RS, 2RSL	70-80%	Rubbing contact, better sealing
Low-friction Seals	2RSH, RSL	80-90%	Reduced friction lip design

Grease Fill Level

Factory fill quantities are optimized to balance lubrication effectiveness against churning losses. Excessive grease causes overheating while insufficient fill leads to early failure. Typical fill is 25-35% of the bearing’s free internal volume.

Life Calculation Factors

Grease life in sealed bearings depends on:

• Operating temperature (higher temperature = shorter life)
• Speed (higher speed = shorter life)
• Contamination (seals provide protection but have limits)
• Load (higher load = more heat generation)

When to Replace

Sealed bearings should be replaced rather than relubricated when:

• Noise or vibration increases
• Temperature rises above normal
• Calculated service life is exceeded
• Seals show visible damage

Selecting Replacement Bearings

When sourcing replacement sealed bearings, note that different manufacturers may use different greases. For critical applications, specify the grease type or purchase from the original manufacturer to ensure consistent performance.