What is Bearing Ring Creep?

 In the daily operation of mechanical equipment, bearings, as one of the core components, play a crucial role in transmission and support. However, the phenomenon of bearing creepage often poses a serious threat to the normal operation of equipment. Today, let's delve into what bearing creepage is, its causes, impacts, and corresponding countermeasures.

1 What is Bearing Ring Creep?

Bearing ring creep refers to the relative movement between the bearing's inner or outer ring and the shaft or housing, leading to friction or wear. Specifically, when the inner ring slides relative to the shaft, it is called inner ring creep; when the outer ring slides relative to the bearing housing, it is called outer ring creep.

Under normal circumstances, the fit between the bearing and the shaft, as well as between the bearing and the housing, is typically an interference fit or a transition fit. This results in significant static friction, ensuring relative motionlessness, and mechanical energy is transmitted through the rotation of rolling elements between the inner and outer rings. However, when this stationary condition is disrupted, creep phenomena occur.

2. The Hazards of Bearing Ring Creep

Bearing ring creep has extremely negative effects on the normal operation of mechanical equipment, which are mainly reflected in the following aspects:

 

(1) Accelerated Component Wear 

Bearing ring creep accelerates the wear of components such as the shaft and bearing housing. During the creep process, increased friction may cause scratches or even grooves to form on the surface of the shaft or housing. This wear not only reduces the precision of the equipment but may also lead to its complete failure.

(2) Reduced Operational Efficiency

Bearing ring creep increases friction, converting a large amount of energy into wasted heat and noise. This not only reduces the operational efficiency of mechanical equipment but can also trigger additional issues, such as lubricant failure or bearing overheating.

 

(3) Impact on Equipment Precision

 

Bearing ring creep may cause a reduction in equipment precision, affecting its normal operation. For instance, in high-precision equipment, ring creep might prevent the equipment from meeting its design specifications, thereby impacting production quality and efficiency.

 (4) Increased Maintenance Costs

Bearing ring creep may lead to frequent equipment failures, increasing maintenance frequency and costs. If the issue of ring creep is not promptly addressed, it could result in more severe equipment damage, potentially requiring the replacement of the entire machine.

 

 

Causes of Bearing Creep (Bearing Outer Ring Rotation)

(1) Fit Tolerance Issues

The fit tolerance between a bearing and its shaft (or bearing housing) must adhere to strict requirements. Various specifications, precision grades, load conditions, and working environments require different fit tolerances. If an inappropriate fit tolerance is selected, such as using a clearance fit, the mutual pressing force is reduced. This can cause the shaft (or bearing) to lose its static positioning and start sliding under the influence of torque, leading to bearing creep.

(2) Insufficient Machining and Installation Accuracy

Failure to meet required standards in machining tolerances, surface roughness, and assembly accuracy of the shaft, bearing, or bearing housing affects the fit tolerance, leading to bearing creep. For instance, during the disassembly or reassembly of bearings, burrs may be removed or deformed, causing the shaft diameter to shrink or the hole diameter to expand. This increases the fit clearance and disrupts the proper tolerance.

(3) Material Issues

Different types of bearings require the use of compatible bearing steels that are high in strength, rigidity, and wear resistance. The friction coefficient of bearing alloys must be low to ensure normal operation and reduce the likelihood of bearing creep.

(4) Other Factors

• Poor Lubrication: Insufficient or degraded lubricating grease can increase friction during bearing operation, potentially leading to bearing creep.
• Abnormal Equipment Operation: Equipment issues such as prolonged overloading of motors or misalignment between the motor shaft and coupling can impose additional stress on the bearing and result in creep.
• Environmental Factors: Harsh operating conditions, such as high temperatures, humidity, or exposure to corrosive gases, may accelerate bearing wear, reduce fit precision, and ultimately cause bearing creep.

Countermeasures for Bearing Outer/Inner Ring Creeping

(I) Preventive Measures

• Strictly Control Fit Tolerances: During the equipment design and selection stages, choose suitable bearings and fit tolerances based on actual working conditions to ensure that the fit between the bearing, shaft, and bearing housing meets the requirements.
• Improve Machining and Installation Accuracy: Strengthen quality control of the machining processes for the shaft, bearing, and bearing housing, ensuring that the machining accuracy and surface roughness meet the standards. During installation, strictly follow the process requirements to avoid changes in fit clearance due to improper installation.
• Use High-Quality Materials: Select suitable bearing materials based on the equipment's operating conditions to ensure that the bearings have adequate strength, rigidity, and wear resistance.
• Strengthen Lubrication Management: Regularly inspect the quantity and quality of lubricating grease, and promptly refill or replace it to ensure the bearing operates in a well-lubricated condition.
• Perform Regular Maintenance and Inspections: Establish a regular maintenance system for equipment. Periodically check the operating condition of the bearing, including temperature, vibration, and noise. Address any abnormalities immediately.

(II) Repair Measures

The response strategy depends on the severity of the bearing ring creep. For minor cases of creeping, no special treatment is usually needed. Simply enhance monitoring and periodically inspect the operating condition of the bearing, such as temperature, vibration, and noise. If there is no significant deterioration in the bearing's operating condition, it can continue to be used, but regular maintenance and lubrication should be ensured.

For severe bearing ring creep, the following repair measures should be taken:

• Sleeving: Add a metal sleeve to the surface of the shaft or bearing housing to restore fit precision.
• Pitting: Create small pits on the surface of the shaft or bearing housing to increase friction and prevent creeping.
• Build-Up Welding: Apply a layer of wear-resistant, corrosion-resistant, or heat-resistant metal to the surface of the component.
• Brush Plating: Use electrochemical methods to deposit a coating on the surface of the component.
• Thermal Spraying: Melt spraying material and atomize it through high-speed gas flow to deposit a coating on the surface of the part.
• Laser Cladding: Apply cladding material to the component surface using laser technology, which is a novel surface modification technique.

While bearing ring creep is a common equipment fault, understanding its causes and risks and adopting effective preventive and countermeasures can minimize its occurrence, extend bearing lifespan, and ensure the proper operation of equipment.