Best Grease for Pillow Block Bearings | 2025 Guide

Proper lubrication is paramount for the optimal performance and extended lifespan of pillow block bearings.

Without it, these critical components are more prone to faster wear and higher friction. This can lead to early bearing failure, causing costly downtime and reduced efficiency.

This guide offers practical tips for choosing the best grease for pillow block bearings. It also covers key lubrication techniques to maintain bearing health and extend their lifespan.

Key Grease Properties

Choosing the right grease for your pillow block bearings hinges on understanding a few critical technical parameters. Selecting the optimal lubricant ensures maximum protection and extends bearing life significantly.

Base Oil Viscosity

The base oil viscosity is a crucial factor, as it determines the lubricant's film strength under different operating conditions.

For pillow block bearings, higher viscosity oils are generally better for slow speeds and heavy loads. They help maintain a strong lubricating film, which is essential for protecting the bearing.

On the other hand, lower viscosity base oils work better for high-speed applications. They help reduce churning and heat generation.

Consistency (NLGI Number)

The NLGI (National Lubricating Grease Institute) number indicates the grease's consistency or hardness. This rating ranges from 000 (extremely fluid) to 6 (exceptionally hard). 

For most pillow block bearings, an NLGI 2 grease is widely recommended. It offers an excellent balance of pumpability and retention within the bearing, ensuring consistent grease lubrication across a variety of applications.

However, specific environmental factors or operating conditions might necessitate a different NLGI grade.

Consistency should not change unduly with temperature or mechanical work.

• Softening at high temps: May cause leakage from bearings/housings.
• Hardening at low temps: Can restrict bearing rotation.

Additives

Grease formulations often include various additives to enhance specific performance characteristics:

• Extreme Pressure (EP) Additives: For high-load applications, EP additives are essential. These compounds form a protective layer on metal surfaces, preventing direct metal-to-metal contact even under severe pressure. When you evaluate EP greases, check if they meet standards like ASTM D2596. This standard measures weld point and load-carrying capacity.
• Corrosion Protection and Water Resistance: The base oil and thickener play a role here, but specific additives boost these properties. Lithium-based greases are common for their good water resistance. However, polyurea greases provide even better water washout resistance and oxidation stability. This makes them ideal for wet or humid places. 

Understanding the distinct characteristics of various grease types, categorized by their thickener, is crucial for selecting the optimal lubricant for rolling element bearings.

Table 1: Common Grease Types by Thickener and Their Key Performance Attributes

Temperature

The operating temperature range is a critical consideration. Grease must maintain its lubricating properties across the full temperature spectrum encountered by the bearing.

• High-Temperature Applications: For applications involving elevated temperatures, synthetic greases often outperform mineral oil-based greases. Synthetics offer superior thermal stability, oxidation resistance, and a wider operating temperature range, making them ideal for demanding high-temperature environments.
• Low-Temperature Applications: In cold environments, grease needs to remain pumpable and flowable. Greases formulated with lower viscosity or specific synthetic base oils can provide reliable lubrication during both startup and ongoing operation.

Table 2: Grease Characteristics by NLGI Grade and Base Oil

To visualize the temperature capabilities of different grease types by their base oil, refer to the chart below.

Top Grease Recommendations

For your pillow block bearings, choosing the right grease is crucial. It maximizes their life and performance in your specific application. The table below organizes various grease recommendations by manufacturer, detailing key properties to assist in your selection.

Table 3: Top Grease Recommendations by Manufacturer for Pillow Block Bearings

How to Grease Pillow Block Bearings

Properly greasing pillow block bearings is as important as selecting the correct lubricant. Adhering to the right techniques ensures the grease effectively protects the bearing, extending its lifespan and preventing premature failure. This section outlines the essential steps for effective bearing lubrication.

Manual Greasing Procedures (Using a Grease Gun)

This method uses a grease gun, is a common way to lubricate pillow block bearings in many industries.

Preparation and Safety

• Before beginning, always prioritize safety and cleanliness.
• Consult Manufacturer Guidelines: Always refer to the bearing and equipment manufacturer's lubrication recommendations. These often specify the type of grease, quantity, and frequency.
• Cleanliness is Key: Ensure the grease gun, fittings, and surrounding area are clean to prevent contaminants from entering the bearing. Even small abrasive particles can cause significant damage.
• Personal Protective Equipment (PPE): Wear appropriate gloves and eye protection.

Determining the Right Grease Quantity

Over-greasing is a common mistake that can be as detrimental as under-greasing. Excess grease can lead to:

• Increased Operating Temperature: Overfilling can cause churning, generating excessive heat that degrades the grease and bearing components.
• Seal Damage: High pressure from over-greasing can blow out seals, allowing contaminants to enter.

General Guidelines:

• New Bearings: For a new pillow block bearing, fill the bearing cavity and housing with grease. Use about one-third to one-half full. Avoid completely packing the housing, as space is needed for excess grease to purge and for heat dissipation.
• Re-lubrication: For routine re-lubrication, add a small, measured amount of grease. A common rule of thumb for re-greasing is to add about 0.005 times D times B grams of grease. Here, D is the bearing's outside diameter in millimeters, and B is the bearing's width in millimeters. However, specific bearing manufacturers often provide precise re-lubrication quantities and intervals.
• Visual Cues: When greasing, listen for changes in bearing noise and feel for temperature fluctuations.

Lubrication Frequency

The frequency of lubrication depends on several factors:

• Operating Conditions: Higher speeds, heavier loads, and higher temperatures(e.g. above 55 °C (130 °F)) generally require more frequent re-lubrication.
• Environmental Factors: Wet, dusty, or corrosive environments necessitate more frequent greasing.
• Grease Type: Some long-life or synthetic greases allow for extended re-lubrication intervals.
• Bearing Type and Size: Larger bearings and those under more severe conditions typically need more frequent attention.

Methods for Determining Frequency:

• Time-Based: The simplest method, based on hours of operation or calendar time.
• Condition-Based: Monitoring techniques, such as vibration analysis and ultrasonic detection, help us determine when relubrication is necessary. In ultrasonic monitoring, a decrease in decibel levels frequently indicates this requirement.
• Calculated Intervals: Many bearing manufacturers provide formulas or charts to calculate re-lubrication intervals. These calculations are based on the bearing's type, size, speed, and temperature.

 Table 4: Recommended Greasing Interval for Different Conditions

Greasing Procedure

1. Stop Equipment (if possible): For safety and effectiveness, it's best to grease bearings while the equipment is shut down and locked out. If greasing while running is necessary, exercise extreme caution.
2. Clean Grease Fittings: Wipe down the grease fitting (Zerk fitting) with a clean cloth to remove any dirt or old grease.
3. Attach Grease Gun: Securely attach the grease gun nozzle to the fitting.
4. Pump grease slowly into the fitting. This allows the grease to distribute evenly within the bearing and prevents excessive pressure buildup. For larger bearings or those with purge ports, continue pumping until a small amount of fresh grease purges from the seals or purge port.
5. Detach the grease gun.
6. Clean Up: Wipe away any purged or excess grease from the fitting and bearing housing to prevent dust and dirt buildup.

Monitoring and Post-Greasing Checks

After greasing, monitor the bearing for any signs of issues:

• Temperature: Check the bearing temperature using an infrared thermometer. Immediately after greasing, a slight temperature increase is normal as the grease distributes. However, it should then return to normal operating temperature.
• Noise and Vibration: Listen for unusual noises or feel for excessive vibration, which could indicate over-greasing or other issues.
• Visual Inspection: Regularly inspect seals for damage or signs of excessive grease leakage.

By following these clear guidelines, you can make sure your pillow block bearings get optimal lubrication. This will improve their performance and help them last longer.  

Automated Lubrication (Centralized Grease Supply Systems)

For extensive bearing arrays, complex machinery, or hazardous environments, centralized grease supply systems offer an efficient, precise, and automated lubrication solution. These systems use a pump to deliver metered grease to multiple lubrication points simultaneously.

Key Advantages:

• Optimal & Consistent Lubrication: Ensures accurate grease delivery at precise intervals, preventing under- or over-lubrication.
• Enhanced Safety & Efficiency: Reduces manual intervention in dangerous areas, leading to prolonged bearing life and minimized downtime.

FAQ

Conclusion

Effective greasing pillow block bearings is crucial for maximizing their performance and lifespan.

For most general uses, NLGI 2 grease with EP additives is your best bet. It offers strong protection against wear and tear. 

Always consider specific operating conditions, such as temperature extremes or food-grade requirements, to make the optimal choice.

Proper lubrication will significantly cut downtime and extend machinery life.