Bearing Temperature Overview: A Practical Guide for Design Engineers

Bearing performance is highly dependent on maintaining safe operating temperatures. Overheating can accelerate wear and cause failures that lead to unexpected downtime for maintenance and costly production delays that impact profitability and customer satisfaction.

The key to avoiding these pitfalls lies in understanding and controlling bearing temperatures as part of your design process. In this bearing temperature overview, you will:

• Learn about normal bearing temperatures and how factors like material composition, ambient conditions, and application type impact acceptable limits.
• Identify strategies you can implement to address high bearing temperatures in the design phase, with useful tips to help mitigate the risk of overheating.
• Discover actionable insights that will help you identify the early warning signs of overheating when testing your design.
• Get our best recommendations for high-quality bearings that will meet the needs of your high-temperature application.

What Are Normal Bearing Temperatures?

The acceptable operating temperature for a standard bearing under normal conditions is typically 160°F or below. However, several factors can influence bearing temperature limits, including: 

Material Composition

Bearings are made from a variety of materials, and they all have different thermal tolerances. The acceptable operating range for all-metal bearings is typically higher than that of ceramic or plastic bearings, or metal bearings with plastic or ceramic components.

For example, Axis 6000 Series Bearings can safely operate at temperatures up to 250°F because they’re made entirely of steel. However, the acceptable temperature range for a steel bearing with a plastic cage or a rubber seal would need to be much lower to prevent damage. 

Ultimately, the safest operating temperature for your bearing will always be within range of its least heat-resistant component.

Ambient conditions

A bearing’s normal operating temperature can be affected by environmental factors like ambient temperature, humidity, and airflow. 

For instance, a bearing in an uncooled or poorly ventilated machine room will likely run hotter than one in a climate-controlled environment like a cleanroom or food processing plant.

Intended application

High-speed and high-load applications generate more friction, which means the acceptable temperature range for these bearings is often higher than what’s typically considered normal. 

For instance, a bearing that consistently operates between 180°F and 200°F may be acceptable in a high-speed application, even though it would likely be a cause for concern in a standard application.

Risk Mitigation: How to Address High Bearing Temperatures in the Design Phase

If your design is expected to operate at high temperatures, you can implement one or more of the following strategies to mitigate the risk of overheating:

Choose All-Steel Bearings

When designing for high-temperature environments, avoid plastic cages, rubber seals, and similar components that can warp, crack, or degrade at high temperatures. Instead, choose an all-steel option like Axis 6000 Series Bearings, which come prefilled with Polyrex EM grease and are rated for temperatures up to 250°F.

Opt for Advanced Heat Stabilization

Heat stabilization is a manufacturing process that increases a bearing’s heat tolerance to 300°F or higher. Heat-stabilized bearings are often best suited for applications that generate enormous amounts of friction or are exposed to extreme or fluctuating temperatures.

If you choose heat-stabilized bearings, be sure to pair them with high-temperature greases and specialized seal materials like Viton^™ or Teflon^™ that can withstand extreme conditions without breaking down.

Decrease Bearing Speed

Reducing bearing RPM is an effective way to control operating temperatures, especially in applications where high speeds generate enough heat to compromise performance. 

Lower rotational speeds reduce friction within the bearing, minimizing the heat generated and helping maintain optimal temperatures for longer periods. By designing for a lower RPM, you can extend the bearing’s service life, reduce maintenance needs, and prevent overheating-related failures. 

This strategy is particularly useful in applications where high load capacities are prioritized over speed, such as heavy machinery and equipment that’s expected to handle continuous or high-torque loads. Axis 6000 Series bearings are rated for speeds between 3,000–28,000 RPM.

Consider Different Lubrication Methods

Choosing the right lubrication method is critical for managing bearing temperatures, as it directly affects heat dissipation and friction. Oil bath lubrication, for example, is ideal for low- to medium-speed applications where consistent cooling is needed. The oil not only reduces friction but also absorbs and disperses heat away from the bearing. 

For higher-temperature or high-speed applications, advanced synthetic oils can provide superior stability and longevity, reducing the frequency of relubrication. In extreme conditions, dry lubricants like graphite or molybdenum disulfide are often used because of their ability to withstand high temperatures that would cause other oils to break down.

Explore Alternative Seal Materials

If seals are necessary for protection, avoid standard rubber options, as they’re best suited for more moderate temperature ranges. Instead, consider advanced materials like fluorocarbon (FKM) or polytetrafluoroethylene (PTFE), which are specially formulated to resist heat, reduce friction, and ensure consistent lubrication. 

FKMs like Viton^TM are particularly effective in applications with frequent temperature fluctuations because they resist thermal degradation and retain flexibility. PTFEs like Teflon^TM, which is known for its low friction coefficient, minimize drag and heat buildup to reduce overall bearing temperatures.

Use Climate Control

In high-temperature applications, climate control measures like ventilation systems, cooling fans, and heat sinks help manage ambient temperatures around the bearing to prevent overheating and reduce wear. 

Ventilation systems improve airflow and reduce ambient temperature, making them a practical choice for enclosed machinery or areas where natural cooling is limited. For more precise control, cooling fans can be integrated to direct airflow across the bearing or housing, which is especially useful in sealed applications like electric motors and gearboxes. 

Heat sinks or radiators are additional options for designs requiring continuous cooling, as they conduct heat away from the bearing to maintain a stable temperature.

Add Temperature Sensors

Integrating temperature sensors into your design offers users valuable, real-time insights that enhance safety and performance. Continuous monitoring allows MROs to identify and address issues like excessive friction, misalignment, or insufficient lubrication before they escalate into catastrophic failures and costly downtime. 

Temperature data from these systems can also be integrated into broader predictive maintenance systems, which is especially useful in mission-critical applications like aerospace, heavy manufacturing, or power generation.

Testing Your Design: The Early Warning Signs of Bearing Overheating

When testing your designs, watch out for these early warning signs of overheating, which may be indicators of improper design, lubrication, or installation:

• High-temperature readings outside the expected range can indicate overheating, even if the readings are stable. 
• Temperatures that fail to stabilize or gradually increase over time may indicate the bearing is generating heat faster than it dissipates, a potential sign of overheating.
• Unusual noises like grinding, squealing, and rumbling are often signs of friction, resistance, or wear that can lead to overheating.
• Increased vibration may indicate misalignment or uneven load distribution, which can increase friction and cause overheating.
• Unexpected changes in the consistency, color, or smell of your lubricant may signal overheating.
• A burning smell or smoke can be an extreme sign of overheating. If you experience this, stop testing immediately and investigate the source.
• Excessive oil leakage can reduce the amount of lubricant inside the bearing, leading to excess friction and overheating. It may also be a sign that heat exposure has caused the lubricant to thin out.
• Sudden temperature spikes or rapid fluctuations after the equipment has warmed up can signal impending failure due to overheating.

Total Bearing Failure? 

If you experience a catastrophic bearing failure during testing, a thorough inspection of its inner components may reveal:

• Discoloration, especially yellow-brown (like straw or wheat), brown, blue, or black marks, can be a sign that heat damage led to the failure.
• Excessive wear, pitting, smearing, or spalling on bearing surfaces, especially rolling elements or raceways, can indicate overheating as the cause of failure.

Pro Tip

For the most accurate assessment during testing, take multiple temperature readings at regular intervals rather than relying on single measurements. This will establish a baseline that allows you to spot sudden spikes or gradual increases that might otherwise go unnoticed. With this information, you can accurately diagnose the issue and make adjustments to your design, materials, or assembly process before going into production.

Axis 6000 Series Bearings: A Solid Choice for High-Temperature Applications

Maintaining optimal bearing temperatures is essential to the success of your designs, especially in high-speed and high-load applications. Axis 6000 Series Bearings are crafted from high-grade 52100 bearing steel with a durable steel cage, which makes them an ideal choice for high-temperature applications. We can also offer heat-stabilized options and help with advanced lubrication systems for applications with operating temperatures above the 250°F limit of Axis 6000 Series Bearings.

Download the spec sheet to access detailed performance data and ensure Axis 6000 Series Bearings meet your design’s exact requirements, or contact your local Axis distributor for tailored recommendations and support.