Mounted bearings are critical components in aggregate and mining operations, where equipment faces extreme conditions like heavy loads, contamination, and constant vibration. Understanding why these bearings fail—and how to prevent it—is essential for maintaining productivity and reducing costly downtime.

Below, we break down the primary causes of mounted bearing failures in mining, cement recycling, and aggregate transport applications and offer actionable solutions. We will also show a quick case study where Timken mounted sealed bearings cut a cement company’s bearing costs in half.

1. Contamination: The Silent Killer

Dust, dirt, and debris are pervasive in mining and aggregate environments. When contaminants breach bearing seals, they mix with lubricants, creating abrasive pastes that accelerate wear. For example, the tail pulley support bearings at the end of a conveyor in gravel processing plants are particularly vulnerable to airborne particles generated during crushing, which contaminate the inside of the bearings.

How It Happens:

• Inadequate Sealing: Standard seals may fail under heavy dust loads, allowing particles to infiltrate bearing housings.
• Installation Errors: Dust intrusion during bearing mounting (e.g., improper handling in open-air quarries) can compromise bearings from day one.

Solutions:

• Sealed Bearings: Opt for triple-layered sealed bearings optimized for better grease retention and protection from mud, water, dust, and salt ingress.
• Regular Cleaning: Implement compressed-air blowouts during maintenance to dislodge debris trapped near seals.
• Proper Bearing Installation: Proper preparation, handling, and installation is essential when performing a quality bearing installation.

2. Lubrication Failures: Too Little or Too Much

Various studies indicate that lubrication issues account for 70 to 80% of bearing failures in industrial settings.

In aggregate conveyors and cement recycling mills, improper lubrication leads to overheating, metal-on-metal contact, and premature wear.

Common Scenarios:

• Under-Lubrication: Causes scraping between rolling elements, generating heat that degrades grease and damages raceways.
• Over-Lubrication: Excess grease churns inside housings, increasing energy loss and temperature spikes.

Best Practices:

• Scheduled Lubrication: It is essential to diagnose how often and how much a mounted bearing requires lubrication in a given environment. Once this is established, schedule regular lubrication and apply precise amounts with a grease gun or other tool to ensure bearings aren’t under- or overlubricated.
• Automated Lubrication Systems: Use centralized lubrication systems to deliver precise grease quantities at scheduled intervals.
• The Right Grease: Using the proper grease for your application is critical to the life expectancy of your mounted bearings. Speed, temperature, and environment all affect the choice of grease.

3. Misalignment: The Hidden Stressor

Misalignment in crushers, conveyors, or cement kilns creates uneven load distribution, leading to localized stress and accelerated fatigue. While some misalignment is expected, it must remain within the manufacturer’s specified limits. A cement recycler addressed its misalignment issues, saving $54,000 annually.

Root Causes:

• Installation Errors: Shaft misalignment during bearing mounting.
• Thermal Expansion: Temperature fluctuations in kilns or grinding mills distort components over time.

Prevention Tactics:

• Laser Alignment Tools: Ensure shafts and housings are aligned within ±0.05mm tolerances during installation.
• Adapter Sleeves: Use adapter sleeve locking mechanism to prevent inner-ring slippage during vibration.

4. Overloading and Shock Loads

Heavy-duty equipment like rock crushers and draglines face dynamic loads that can exceed bearing design limits. Overloading creates spalling (surface fractures in raceways and bearings) and catastrophic failures, which is especially problematic with the mounted tapered roller bearings commonly used in mining.

Contributing Factors:

• Impact Loads: Sudden jolts from oversized rocks in crushers.
• Bearing Selection Errors: Using bearings with insufficient load ratings for conveyor systems.

Mitigation Strategies:

• Load Monitoring: Install real-time sensors to track radial and axial forces.
• Upgraded Bearings: Switch to spherical or tapered roller bearings, which handle combined radial/axial loads and self-align under stress.

5. Vibration & Thermal Stress

Aggregate conveyors and vibrating screens generate intense oscillations that loosen bearing components. In one case, vibration-induced grub screw loosening caused a recycling plant’s bearings to fail every three months until they adopted vibration-resistant designs.

Key Impacts:

• Grease Displacement: Vibration expels lubricant, leaving bearings dry.
• Thermal Expansion: High temperatures from friction degrade seals and grease.

Countermeasures:

• Vibration Dampers: Install rubber-mounted housings on screening equipment.
• Heat-Resistant Materials: Use bearings with brass cages or ceramic rolling elements for high-temperature applications.
• Vibration Sensors: Install sensors to directly feed vibration frequency and temperature data to watch for unusual changes from baseline operating values.

Case Study: Timken Solves Mounted Bearing Failures in Aggregate & Concrete Company

In the demanding environment of an aggregate and ready-mix concrete operation, conveyor systems constantly contend with coarse and fine aggregates mixed with water. This combination leads to material buildup, increasing wear on components. One company experienced frequent premature mounted bearings failures on its conveyors, resulting in unplanned downtime and costly repairs.

Solution & Results

To address the issue, a Timken distributor recommended upgrading to Timken® Type E mounted tapered roller-bearing and Timken® solid block-mounted spherical roller bearings with end cover options. These solutions were designed to withstand heavy contamination and extend bearing life.

The newly installed Timken mounted bearings significantly improved performance in the harsh operating conditions, doubling the service life compared to the previous competitor’s bearings. As a result, the company reduced the frequency of mounted bearing replacements, with some plants cutting their annual bearing costs in half. This proactive switch minimized unexpected downtime and improved overall efficiency.

Mounted Bearing Proactive Maintenance: A Checklist for Professionals

1. Contamination Control

• Inspect seals monthly for cracks or wear.
• Use desiccant breathers in humid environments.

2. Lubrication Management

• Conduct grease analysis every 500 operating hours.
• Train staff on proper grease gun techniques to avoid over-packing.

3. Alignment and Load Checks

• Perform laser alignment biannually.
• Monitor load sensors for deviations exceeding 10% of design limits.

4. Vibration Analysis

• Deploy wireless accelerometers to detect abnormal frequencies early.

Technicians can significantly enhance equipment reliability in aggregate and mining sectors by addressing these failure modes through robust bearing selection, precise maintenance, and advanced sealing technologies. The right combination of preventive strategies reduces downtime and extends mounted bearing life by up to 3x in harsh environments.

Timken Delivers Mounted Bearing Solutions

Timken’s mounted solid-block spherical roller bearings offer unrivaled multi-point seal design for optimal performance in the highly contaminated environments present in aggregate and mining applications. They offer a wide range of mounted bearing solutions to counter contamination, shaft misalignment, dynamic loads, and more.

Explore Timken’s Mounted Bearings

Mounted Solid Block Spherical Roller Bearings for extreme environments.

Shop Bearings Now

Do you have problems with frequent mounted bearing failures? IBT Industrial Solutions’ industrial maintenance technicians offer bearing troubleshooting, vibration analysis, precision shaft alignment, and failure analysis services.