What Causes "Seizure" of Rolling Bearings, and How Should It Be Dealt With?

Bearings "Seizing Up": A Common Challenge for Mechanical and Electrical Engineers

Bearing "seizing up" is a troublesome issue that often plagues mechanical engineers and motor engineers. It not only leads to equipment downtime but may also cause more severe equipment damage. Today, let's delve into the definition, main causes, and effective solutions for the "seizing up" of rolling bearings.

1. What Does Bearing "Seizing Up" Mean?

Bearing "seizing up" refers to the situation where rolling bearings, during operation, experience conditions that prevent the rolling elements inside the bearing from rotating properly. This results in severe friction resistance between the bearing and either the shaft or the housing, potentially reaching a point where rotation becomes entirely impossible. This phenomenon is usually accompanied by abnormal vibrations, increased noise, and a sharp rise in temperature. Ultimately, it may cause equipment failure or even damage. Bearing "seizing up" is a serious fault condition that requires timely detection and intervention to avoid greater damage to the equipment.

2. Main Causes of Bearing "Seizing Up"

(1) Poor Lubrication

• Insufficient Lubricating Oil
Lubricating oil plays an essential role in bearing operation. When the amount of oil is insufficient, the friction coefficient of the bearing increases significantly. Under normal circumstances, lubricating oil forms a thin oil film between the rolling elements and raceways, providing lubrication and cushioning. If the oil quantity decreases, the oil film becomes thin or even disappears, leading to direct contact between the rolling elements and raceways, resulting in dry friction. For instance, in some long-running motor equipment, failing to replenish lubricating oil in time may cause the bearing to overheat due to friction. The heat generated cannot dissipate effectively, and the bearing may eventually seize up.

• Degraded Lubricating Oil
The quality of lubricating oil is equally critical. If the oil becomes contaminated or is used for too long, its performance will gradually deteriorate. Contaminants, moisture, or oxidation of the lubricating oil can significantly reduce its lubrication properties. Contaminants may enter the bearing, scratching the raceway and rolling element surfaces, which increases friction resistance. A degraded lubricating oil fails to form an effective oil film, causing greater resistance during operation, eventually leading to bearing seizure. For example, in machinery operating in harsh environments, lubricating oil is prone to contamination from dust or metal debris. If not replaced promptly, it can easily result in bearing failure.

 

(2) Overload Operation
• Mechanical Overload
When equipment operates beyond its designed load capacity, it can exert extreme pressure on bearings. Bearings are designed with a specific load-bearing capability, and if the actual load exceeds this limit, the rolling elements and raceways inside the bearing will be excessively compressed. For example, in some heavy machinery, running equipment under overload conditions may cause the rolling elements of the bearing to deform due to excessive compression, and the raceways may develop indentations. These issues increase the operating resistance of the bearing and may eventually cause it to seize.

• Thermal Overload
In addition to mechanical overload, thermal overload is another critical factor. When equipment operates in an environment with excessively high temperatures or when the bearing itself has poor heat dissipation, the lubricant inside the bearing may lose viscosity due to high temperatures or even vaporize. Additionally, the metal components of the bearing may deform due to thermal expansion. For example, in electric motors working in high-temperature environments, an inadequately designed cooling system can lead to excessively high bearing temperatures, potentially reducing the internal clearance of the bearing. This increases friction between rolling elements and raceways and may ultimately cause the bearing to seize.

(3) Improper Installation
• Installation Misalignment
The installation accuracy of bearings is critical to equipment operation. If bearings are installed with errors such as axial misalignment, radial tilt, or insufficient fastening, it can compromise the normal functioning of the bearing. For instance, axial misalignment may result in uneven contact between the rolling elements and raceways, causing localized overload. Radial tilt can lead to uneven gaps between the inner and outer rings of the bearing, increasing operating resistance. These installation errors can worsen during equipment operation and may eventually cause the bearing to seize.

Improper Use of Installation Tools

  • Improper Tool Usage
    • When installing bearings, using inappropriate tools or improper methods may damage the bearing. For instance, directly hitting the bearing with a hammer may cause cracks or deformation in the rolling elements or raceways. Such damage will progressively worsen during operation and eventually lead to bearing seizure. The correct installation method involves using specialized bearing installation tools such as hydraulic installation tools or heat installation tools to ensure the bearing is evenly stressed and installed smoothly.

Foreign Object Intrusion or Contamination

  • Foreign Object Intrusion

    • When foreign objects like dust, sand, or metal debris enter the interior of a bearing, they can severely impact its normal operation. These objects may get lodged between the rolling elements and the raceways, scratching the raceway surface and increasing frictional resistance. For example, in outdoor machinery, if the bearing's sealing design is inadequate or damaged, dust and sand can easily enter the bearing. The presence of foreign objects can destroy the oil film formed by the lubricant, leading to direct contact between rolling elements and the raceways, causing dry friction. This ultimately may result in bearing seizure.

  • Contamination

    • Contamination of lubricant is another major cause of bearing seizure. When lubricant mixes with water, impurities, or chemical substances, its lubricating properties can significantly degrade. For instance, in humid environments, lubricant may absorb water, which reduces its viscosity and prevents the formation of an effective lubrication film. Additionally, chemical contamination may lead to reactions that produce corrosive substances, which then corrode the bearing's metal surface, exacerbating wear and damage, eventually leading to seizure.

Bearing's Own Quality Issues

  • Manufacturing Defects

    • Manufacturing defects in bearings, such as inconsistent rolling element sizes or rough raceway surfaces with cracks, can affect performance. For example, inconsistencies in rolling element sizes may cause vibration and noise during operation, increasing operational resistance; rough raceway surfaces or cracks may generate extra friction at the rolling element-raceway interface. These issues can result in bearing seizure. Therefore, choose bearings from reliable, reputable brands and suppliers.

  • Material Issues

    • The material quality of bearings is another crucial factor affecting performance. If the bearing material is substandard—for instance, inadequate hardness, insufficient toughness, or poor corrosion resistance—it may result in wear, deformation, or corrosion during operation. For example, in environments with humidity or corrosive gases, if the bearing material lacks corrosion resistance, the surface may corrode and form rust, increasing operational resistance and potentially leading to seizure.

Methods to Resolve Bearing Seizure

(I) Lubrication Management

  • Periodic Inspection of Lubricant

    • Establish a comprehensive lubrication management system for regular inspection of lubricant levels and quality. Depending on equipment type and operating environment, determine appropriate inspection intervals. For instance, for equipment operating under harsh conditions and heavy loads, inspections might need to occur weekly. For equipment with favorable operating conditions and lighter workloads, monthly inspections may suffice. If lubricant levels are found to be insufficient or quality is compromised during inspections, promptly replenish or replace the lubricant.

  • Optimization of Lubrication System Design

    • For large-scale equipment or machinery requiring high lubrication standards, consider optimizing the lubrication system design. For instance, implementing automatic lubrication systems can dynamically adjust lubricant supply based on operational status, ensuring bearings remain properly lubricated. Moreover, adding filtration systems to the lubrication setup can prevent contaminants from entering the lubricant, maintaining its cleanliness. For equipment operating in high-temperature environments, a circulating cooling lubrication system may be employed to cool the lubricant, reducing bearing temperatures, and extending service life.

  • (2) Load Control

    • Reasonable Design of Equipment Load
      During the design phase of equipment, it is essential to fully consider the bearing’s load capacity and reasonably design the load range. Based on the actual usage needs and working environment, select the appropriate bearing model and specifications to ensure that the bearing operates normally within the designed load range. For example, when designing heavy machinery, choose bearings with sufficiently high load capacity according to the load characteristics of the equipment. Additionally, during equipment operation, strictly control the load to ensure it does not exceed the design limits.

    • Enhancing Equipment Operation Monitoring
      For equipment already in operation, strengthen the monitoring of its operational status and promptly identify instances of overload operation. This can be achieved by installing sensors to monitor parameters such as load, temperature, and vibration in real-time. For instance, when the load of the equipment exceeds the preset value, the sensors can issue an alarm, alerting the operator to take immediate measures, such as reducing the equipment's operating speed or load, to prevent bearings from seizing due to overload. Furthermore, data analysis can be used to evaluate the operation status of the equipment, predict possible failures in advance, and perform timely maintenance and upkeep.

    (3) Installation and Maintenance

    • Standardized Installation Procedures
      When installing bearings, strict adherence to standardized procedures is essential. First, ensure the cleanliness of the installation environment to prevent dust, debris, and other impurities from entering the bearings. Second, use suitable installation tools and methods, such as hydraulic tools or heat-fitting tools, to ensure the bearings are evenly loaded and properly installed. During the installation process, check the alignment precision of the bearings, such as axial offset and radial tilt, and ensure that the installation deviations are within permissible limits. For example, when installing large motor bearings, you can use tools like laser alignment devices to accurately measure and adjust the bearing installation position, ensuring installation precision.

    • Regular Maintenance and Inspection
      Establish a regular maintenance and inspection system to periodically check and service the bearings within the equipment. Inspection contents include the bearing’s appearance, operating condition, and clearance size. For example, regularly check the bearing surface for wear, cracks, or rust; measure bearing vibration and noise to determine whether its operation is normal; and use tools such as feeler gauges to check bearing clearance size. If the clearance is too large or too small, timely adjustments or replacements should be made. Regular maintenance and inspection help identify potential issues early and address them proactively, preventing bearing seizure failures.

    • (4) Quality Control

      1. Selecting High-Quality Bearings
        When purchasing bearings, it is crucial to choose brands and suppliers with reliable quality and good reputation. You can verify the quality of bearings by checking their manufacturing credentials, quality inspection reports, and other related documents. Additionally, refer to user reviews and feedback to select bearings with good cost-performance ratios. For instance, some well-known bearing brands utilize advanced manufacturing techniques and implement strict quality control systems during production, ensuring a certain level of quality and performance for their products.

      2. Enhancing Quality Inspection
        For bearings purchased, conduct strict quality inspections before installation and use. Examine whether the bearings have visible damage, confirm their dimensions meet requirements, and ensure the surface quality of rolling elements and raceways is adequate. For example, use tools such as micrometers to measure dimensional accuracy, and employ microscopes or similar equipment to inspect surface roughness and detect cracks or other defects. Only bearings that pass quality inspections should be installed and used on equipment to prevent seizure failures originating from bearing quality issues.

      Rolling bearing "seizure" is a complex engineering problem with diverse causes, including poor lubrication, overload operation, improper installation, and issues related to bearing quality. However, by focusing on lubrication management, load control, installation and maintenance, and quality control...

 

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