High Temperature Bearings: Guide to Load Capacity

High temperature bearings are important for machines that work in hot conditions. They keep things running smoothly and safely, even when the job is tough.

Understanding and optimizing load capacity helps machines work better and last longer. It also enhances their energy efficiency. This reduces downtime and costs. It also boosts productivity and reliability.

This blog explains why high temperature bearings are important. It also shows how understanding load capacity improves performance and service life.

It covers key factors that affect load capacity and tips for optimizing performance. It also highlights mistakes to avoid when choosing bearings for tough conditions. Learn how to keep your machines running smoothly and reduce downtime.

What is Load Capacity in High-Temperature Bearings?

Defining Load Capacity

Load capacity is the maximum weight a bearing can safely support without breaking or wearing out. It keeps the bearing working well over time and extends the life of the machinery.

Static Load Rating (C₀): The Static Load Rating (C₀) is the maximum weight a bearing can handle without getting damaged. This applies when the bearing is not moving and is under a static load.

Dynamic Load Rating (C): The dynamic load rating (C) is the maximum weight a bearing can handle while rotating. This rating is based on a specified number of turns, typically 1 million rotations. It shows how well the bearing can support loads during use without wearing out or breaking.

Static Load vs Dynamic Load

• Static Load Rating (C₀) applies to stationary conditions. It focuses on the bearing's ability to resist deformation under a load that does not move.
• Dynamic Load Rating (C) applies to moving conditions. It focuses on the bearing's ability to support rotational loads over time without failing.

Static Load Rating (C₀)

• Axial Loads: The static load rating helps determine how much axial (push or pull) load the bearing can withstand. This is without causing permanent deformation when the bearing is stationary. A higher C₀ rating means the bearing can handle larger axial forces without damage.
• Radial Loads: It also applies to radial loads (force from the side) when the bearing is not moving. Bearings with a higher static load rating can handle more radial force without getting damaged.
• Combined Loads: When both axial and radial forces are applied, the bearing must resist both types of load. It needs to handle these forces simultaneously without causing damage. The static load rating helps ensure the bearing remains intact under such combined stress.

Dynamic Load Rating (C)

• Axial Loads: The dynamic load rating shows how well the bearing can handle axial loads while rotating. A higher rating means the bearing can support heavier forces without wearing out or failing.
• Radial Loads: It also applies to radial loads while the bearing is rotating. Bearings with a high dynamic load rating can handle more radial forces without wearing out quickly.
• Combined Loads: The dynamic load rating shows how well the bearing can handle axial and radial loads. It measures the bearing’s ability to withstand these forces while in motion. Bearings need to be built to support both types of load for smooth operation and to prevent failure.

Importance of Load Capacity in High-Temperature Applications

Extreme heat can have a significant impact on bearings and their components

• Materials: High temperatures can weaken materials, causing them to lose strength, flexibility, or even deform. This can lead to premature failure if the bearing isn't designed to handle such heat.
• Lubrication: Heat can break down lubricants, making them less effective. Insufficient lubrication leads to an increase in friction. This can lead to overheating, wear, and possible bearing damage.
• Internal Clearances: As materials expand in high heat, internal clearances within the bearing can change. This can affect the smooth movement of the bearing and lead to increased wear or even seizing under extreme conditions.

Load capacity is directly linked to common bearing issues like wear, misalignment, and premature failure

• Bearing Wear: When a bearing is subjected to loads beyond its capacity, excessive friction occurs. This results in faster wear and potential damage to the bearing. This can cause the bearing surfaces to degrade, reducing its effectiveness and lifespan.
• Misalignment: If the bearing load is too high or not evenly spread, it can cause misalignment. This leads to uneven stress, increasing wear, vibration, and eventually causing the bearing to fail.
• Premature Failure: Overloading a bearing can make it fail sooner than expected. Too much stress can cause the material to weaken, overheat, or break down.

Key Factors Affecting Load Capacity in High-Temperature Bearings

Material Composition

Ceramics

• Features: Ceramics, like silicon nitride, are strong, smooth, and resistant to wear and heat. Additionally, they are non-magnetic in nature.
• Uses: They are used in precise equipment, aerospace, and medical devices where reliability is key.

Graphite-Coated Steels

• Features: Graphite-coated steel combines the strength of steel with graphite’s ability to reduce friction. It works well in dry or hot conditions.
• Uses: These bearings are used in high-temperature machines or places where lubricants don't work well.

Special Alloys

• Features: Special alloys, like stainless steel or bronze, are made for strength, heat resistance, and corrosion protection.
• Uses: These are used in cars and industrial machines. They are also used in marine equipment where durability is needed.

Lubrication Technology

Graphite-Based Lubrication

• How It Works: Graphite-based lubrication uses fine graphite particles to create a thin layer between moving parts. The graphite acts as a dry lubricant, reducing direct contact between surfaces.
• Reducing Friction: Graphite’s natural lubricating properties lower the friction between bearing surfaces. This helps them move smoothly without generating excessive heat.
• Enhancing Load Capacity: By reducing friction, graphite-based lubrication helps the bearing handle higher loads. This prevents overheating and wear, improving the bearing’s longevity. It helps distribute the load more evenly, improving the bearing’s performance under stress.

Other Lubrication Methods

• Grease: Grease is often used in bearings to create a thicker lubrication layer. This helps protect the bearing from contamination and reduces wear. It can withstand moderate to high temperatures.
• Oil: Oil lubrication is effective in high speed bearings. It flows easily, reducing friction, and can carry heat away from the bearing, enhancing its load capacity and lifespan.
• Dry Lubricants: In environments where liquid lubricants cannot be used, such as vacuum chambers, dry lubricants are necessary. These lubricants provide the required protection and reduce friction in such conditions. Graphite and molybdenum disulfide reduce friction without needing oils or grease.

Here’s a comparison between lubrication-free bearings and traditional grease-lubricated bearings:

Operating Conditions and Load Distribution

Low Rotational Speeds

• Effect: Bearings for low-speed applications can handle heavier loads because there is less friction and heat.
• Example: Conveyors are used to transport heavy materials at a slow and controlled pace. Bearings in these systems must support the weight without wearing out quickly.

Axial Loads (Along the Shaft)

• Effect: Axial loads push or pull along the shaft. Bearings need to handle these forces without misalignment or damage.
• Example: Ovens in industries often use bearings to support rotating trays or racks. These bearings must handle the forces pushing along the shaft to keep things running smoothly.

Radial Loads (Perpendicular to the Shaft)

• Effect: Radial loads apply pressure at right angles to the shaft. Bearings must manage this stress to avoid damage or misalignment.
• Example: Cooling beds in metal production need bearings to support heavy rolls that move metal. These bearings must bear the weight without failing.

Real-World Examples

• Conveyors: These work with low speeds and high radial loads. Bearings must carry weight without too much friction, ensuring smooth operation.
• Ovens: Bearings here need to handle axial loads as trays or racks rotate. They must endure pressure along the shaft.
• Cooling Beds: Bearings support heavy radial loads as they move metal. They must be strong enough to bear the weight.

Environmental Challenges

Contaminants, humidity, and corrosive conditions can reduce bearing efficiency and load capacity in the following ways

• Contaminants (dirt, dust, etc.): Contaminants can get into the bearing and cause friction, wear, and damage. This makes the bearing less efficient and reduces its ability to handle heavy loads.
• Humidity (moisture): Moisture can cause rust and corrosion inside the bearing. This weakens the materials, increases friction, and can eventually lead to bearing failure.
• Corrosive Conditions: Exposure to chemicals or salt can cause corrosion of the bearing’s materials. This leads to damage, increased wear, and a reduction in load capacity. This makes the bearing unable to support the required weight effectively.

Here are some ways to protect bearings from contaminants, moisture, and corrosive conditions

• Labyrinth Seals: These seals form multiple barriers that stop dirt and dust from getting into the bearing. They are effective in harsh environments.
• Lip Seals: Lip seals have a flexible edge that forms a tight contact with the bearing’s surface. They help prevent moisture and contaminants from entering while keeping lubrication inside. They are suitable for moderate-speed and load applications.
• Metallic or Elastomeric Seals: These seals create a strong barrier against harmful chemicals or high pressure. They are perfect for protecting bearings in tough environments like chemical or marine industries.
• Contact Seals: Contact seals are designed to form a tight seal against the bearing's inner surface. They prevent contaminants such as dust and moisture from penetrating the bearing. This helps reduce friction, ensuring the bearing lasts longer in challenging environments.
• Non-contact Seals: These seals stop contamination without touching the bearing surface, reducing wear and friction. They are good for situations with light contamination.
• Grease or Oil Seals: These seals keep grease or oil inside the bearing. This provides an extra layer of protection against contaminants and moisture. This helps reduce the risk of corrosion and wear.

How to Calculate and Select Bearings Based on Load Capacity

Calculating Load Capacity

Equivalent Static Load (P₀)

This is the combined load that causes the same stress as the actual loads on the bearing.

P0​=X⋅Fa​+Y⋅Fr​

• P₀ = Equivalent static load
• F_a = Axial load (along the shaft)
• F_r = Radial load (perpendicular to the shaft)
• X and Y = Load factors (depend on the bearing type)

Required Basic Static Load Rating (C₀req)

This is the load capacity needed to avoid bearing damage under static conditions.

C0req=P0/f0​​

• C₀req = Required load rating
• P₀ = Equivalent static load (calculated earlier)
• f₀ = Safety factor (usually between 1.5 to 2)

Using Manufacturer Load Rating Tables

Key Terms You’ll See in Load Rating Tables

Dynamic Load Rating (C)

The load a bearing can handle while rotating, used to predict bearing life.

• Static Load Rating (C₀):

The load a stationary bearing can handle without being permanently deformed.

• Equivalent Dynamic Load (P):

A combination of forces (radial and axial) acting on the bearing.

• Life Expectancy (L₁₀):

The number of revolutions or hours at a certain load before 90% of bearings in a group

To read load rating tables, begin by identifying your needs, such as the type of load (radial, axial, or both). Also, consider factors like operating speed and the required lifespan. Find a bearing in the table that matches your size requirements. Make sure the Dynamic Load Rating (C) is higher than your load and the Static Load Rating (C₀) can handle heavy, stationary loads.

Use the formula L10=(C/P)3 to check if the bearing life meets your needs, where P is your actual load. Also, confirm the bearing’s speed rating works for your application. Choose a bearing that fits all these factors.

Best Practices for Bearing Selection

Understand Application Requirements

• Operating Temperature Range: Figure out the highest and lowest temperatures the bearing will face during operation. This includes regular working conditions and any extreme situations, like startup or shutdown.
• Load Conditions: Evaluate the radial and axial loads the bearing will need to handle. Make sure to consider both static forces (when the bearing isn’t moving) and dynamic forces (during operation).
• Speed Requirements: Determine the rotational speed of the bearing in revolutions per minute (RPM) required for the application.
• Environment: Assess whether the bearing will be exposed to moisture, dust, or chemicals. Evaluate the potential impact of these contaminants on the bearing’s performance and lifespan.

Choose the Right Bearing Material

• Steel Bearings: Suitable for moderate high-temperature applications. Seek materials such as heat-treated or alloyed steel.
• Ceramic Bearings: Ceramic bearings is ideal for high temperatures. Also resistant to corrosive environments, the material ensures long-lasting performance.
• Special Coatings: Consider bearings with protective coatings for additional durability.

Select the Appropriate Lubrication

• High-Temperature Grease: Ensure it matches the operating temperature range and resists oxidation.
• Dry Lubrication: Use solid lubricants like graphite or molybdenum disulfide for high temperatures.
• Oil Lubrication: Suitable for high-speed applications but may degrade at extreme temperatures.

Verify the Bearing Design

• Sealed vs. Open Bearings: Sealed bearings protect against contamination; open bearings are better for high heat dissipation.
• Internal Clearance: Select a larger internal clearance (e.g., C3, C4) to accommodate thermal expansion.
• Cage Material: Choose metal or heat-resistant polymer cages for stability at high temperatures.

Consider Longevity and Maintenance

• Durability: Opt for materials and lubricants designed to withstand prolonged high-temperature exposure.
• Maintenance Needs: Determine if the bearings will require periodic relubrication or inspection.

Review Manufacturer Specifications

Check the maximum temperature rating, speed limits, and load capacities in the manufacturer’s datasheet.

Test and Validate

Conduct a trial run in actual operating conditions to ensure the bearing performs as expected.

Consulting manufacturers or bearing specialists for expert advice is a good idea. They can help you choose the best bearing for your specific needs and conditions.

Enhancing Load Capacity for High-Temperature Bearings

Installation Techniques

Proper alignment and securing methods are crucial to ensure the bearing operates efficiently. They help distribute the load evenly across the bearing. This prevents unnecessary stress and extends the bearing’s lifespan.

Leave enough space between the bearing and its housing during installation. This enables the bearing to expand as it experiences increased temperature. Use bearings with extra clearance (like C3 or C4) to allow for this.

Avoid fitting bearings too tightly during installation. Consider using materials or coatings that can withstand high temperatures without deforming.

Maintenance Practices

Running-in new bearings enhances their performance and ensures smoother operation. Start with a light load to let the parts adjust and reduce friction. Slowly increase the load while checking the temperature and noise.

Make sure the bearing is properly lubricated to avoid wear and overheating. This process helps the bearing last longer and work efficiently.

Regular inspections are key to monitoring load conditions and preventing overload. Check the bearing for signs of wear, unusual noise, or temperature changes.

Ensure it’s still handling the correct load, and adjust if needed. Regularly lubricate the bearing and clean it to maintain proper function. Early detection of problems can help prevent damage and extend the bearing’s life.

Upgrading to Specialized Bearings

For tough applications, choose bearings with advanced features like graphite lubrication or strong materials. Graphite lubrication works well in high temperatures and reduces friction. Bearings made from tough materials like ceramic or strong alloys last longer and resist wear, corrosion, and heavy loads. These bearings are great for extreme conditions, providing reliable performance.

SKF offers bearings with graphite lubrication, ideal for high temperatures and reducing friction. They offer bearings made from durable materials such as ceramic and high-strength alloys. These materials are resistant to wear, corrosion, and can withstand heavy loads. These advanced features make SKF bearings perfect for extreme conditions, ensuring reliable and long-lasting performance.

Common Mistakes and How to Avoid Them

Overlooking Operating Conditions

Neglecting factors like heat, contaminants, and load misalignments can lead to bearing failure. High temperatures can degrade bearings if they aren't designed for heat resistance.

Exposure to contaminants like dirt or moisture can cause wear and corrosion. Misalignments in load distribution can put extra stress on the bearing, shortening its lifespan. Always consider these factors to ensure proper bearing selection and avoid costly damage.

Misjudging Load Requirements

Underestimating or overloading bearings can cause serious problems. Overloading can cause quick wear and high friction. This may lead to overheating, damaging the bearing.

Underestimating the load can make the bearing work inefficiently, reducing its lifespan. Both can result in failure, causing costly repairs and equipment damage. Always choose the right bearing for the load to avoid these issues.

Skipping Regular Maintenance

Neglecting maintenance can make bearings wear out faster and lose their ability to handle loads. Without proper care, things like poor lubrication or dirt can cause damage. This leads to unexpected downtime for repairs, which increases costs. Regular maintenance helps bearings last longer and keeps them working smoothly.

Applications and Case Studies

Real-World Applications

• Food Processing: High temperature bearings can handle heat and moisture. This helps them perform reliably in places with temperature changes or where water and steam are present.
• Steel Manufacturing: These bearings can withstand extreme temperatures and heavy loads. This makes them ideal for the high-stress, high-temperature conditions commonly encountered in steel production.
• Automotive Production: High temperature bearings resist heat and moisture. This helps them work reliably in places with temperature changes or where they may be exposed to water or steam. High temperature bearings are used in applications like ovens, conveyor systems, and paint drying lines. In ovens, they handle the intense heat while ensuring smooth operation. Conveyor systems rely on high temperature bearings to work effectively at elevated temperatures. In paint drying lines, these bearings maintain performance under heat exposure. This helps ensure a consistent and efficient process.

Case Study: Load Capacity in Action

In a steel manufacturing plant, SKF high temperature bearings were installed in conveyor systems. These systems were exposed to extreme heat and heavy loads.

By switching to SKF bearings, the plant improved load handling and reduced wear. This resulted in a 30% increase in uptime and a 25% reduction in maintenance costs. Fewer bearing failures and less downtime for repairs contributed to these improvements.

FAQ Section

• What is the difference between static and dynamic load capacity?

The static load capacity is the most weight a bearing can support when it is not moving. The dynamic load capacity is the most weight a bearing can handle while it is moving without getting damaged.

• How do I calculate equivalent static load for bearings?

To calculate the equivalent static load for bearings, combine the radial load (Fr) and axial load (Fa). Use this formula:

P0=X0⋅Fr2+Y0⋅Fa

Where:

P0= Equivalent static load (N or lbf)

Fr= Radial load (N or lbf)

Fa= Axial load (N or lbf)

X0= Radial load factor (from bearing tables)

Y0= Axial load factor (from bearing tables)

• What are the best materials for high temperature bearings?

The best materials for high temperature bearings include ceramic, such as Silicon Nitride, for excellent heat resistance. Stainless steel or titanium are also ideal for their strong performance in high-heat conditions. Chrome steel and carbon-graphite are also good options for durability and wear resistance.

Conclusion

Understanding the load capacity of high temperature bearings is important to ensure they work reliably. It also helps prevent them from failing too soon. Optimizing this helps the bearings last longer in tough conditions.

Choosing the right bearing for your needs is important to keep things running smoothly. Regular maintenance helps the bearing last longer. Following the manufacturer’s guidelines ensures it works properly and avoids problems.

To choose the right bearing for your needs, explore our range of high-quality products. You can also contact our experts for personalized recommendations. Let us help you find the perfect solution to optimize your equipment’s performance!