Causes of Excessive Bearing Temperature and Effective Solutions
Excessive bearing temperature—often described as an abnormal “fever” condition—is a common and highly damaging fault in rotating equipment.
If the root cause is not identified promptly and handled properly, corrective actions may be ineffective, leading to:
Reduced bearing service life
Increased maintenance costs
Severe damage or even bearing burnout
Therefore, quickly identifying the cause and taking appropriate corrective measures is critical to ensuring continuous, safe, and stable equipment operation.
Below are the most common causes of excessive bearing temperature and corresponding solutions.
1. Poor Lubrication
Lubrication plays a vital role in bearing performance, affecting friction, wear, vibration, and service life.
Statistics show that approximately 40% of bearing failures are related to poor lubrication.
Functions of Proper Lubrication
Prevents metal-to-metal contact and corrosion
Acts as a seal to prevent foreign material intrusion
Dissipates frictional heat and limits temperature rise
Reduces friction and wear, extending bearing life
Common Causes of Poor Lubrication
Insufficient lubricating oil or grease
Blocked lubrication pipelines due to foreign matter
Poor-quality or unsuitable lubricating grease
Failure to lubricate at specified intervals
Lubricant contamination by dust or impurities
2. Bearing Wear
Bearings are critical components used across a wide range of machinery.
In dusty environments—such as air compressor applications—fine particles may enter the bearing housing, contaminating the lubricant and causing deterioration.
As wear increases:
Friction rises
Heat generation increases
Bearing temperature continues to climb
Operating bearings in a worn condition significantly accelerates failure.
3. Improper Installation
Incorrect bearing installation is another major cause of overheating.
Key installation requirements:
The shaft centerline and bearing housing centerline must be perfectly aligned
Installation accuracy directly affects bearing life and machine precision
Improper installation may lead to:
Bearing deflection
Additional torque during rotation
Increased vibration and noise
Accelerated wear and temperature rise
4. Insufficient Cooling
Insufficient cooling is commonly caused by:
Blocked lubrication or cooling pipelines
Improper cooler selection
Poor cooling efficiency
These issues prevent effective heat dissipation, resulting in elevated bearing temperatures.
5. Cooler Fouling and Blockage
Cooler fouling is especially common during summer operation.
Typical issues:
Scale buildup inside the cooler
Blocked lubrication cooling channels
Frequent high-temperature alarms
Recommended solution:
Perform acid cleaning and descaling of coolers before summer to restore cooling efficiency.
6. Excessive Vibration
Bearing temperature rise may also result from excessive vibration caused by:
Improper coupling alignment
Rotor dynamic or static imbalance
Insufficient foundation rigidity
Loose anchor bolts
Rotating stall or surge
Vibration can create indentations, cracks, and fatigue damage on bearing raceways and rolling elements, accelerating heat generation.
Regular inspections should be conducted according to specified maintenance intervals.
7. Poor Bearing Quality
Bearings operate under long-term alternating contact stress (point or line contact).
The accuracy, reliability, and service life of the entire machine largely depend on bearing quality.
Recommendations:
Use bearings from reputable manufacturers
Conduct strict inspection during procurement and acceptance
Reject bearings with defects, poor surface finish, or dimensional inaccuracies
8. Improper Bearing Selection
When selecting bearings, it is essential to consider:
Rated load capacity
Maximum allowable speed
Operating temperature
Operating bearings under overload or overspeed conditions will significantly shorten service life and increase failure risk.
Effective Measures for Bearing Cooling
1. Improper Grease Quantity (Too Much or Too Little)
Bearings should be lubricated strictly according to operating requirements
Excessive grease often causes temperature spikes
Typically, temperature rises by 10–15°C above normal, stabilizes, and then gradually decreases
2. Incorrect or Contaminated Grease
Problems include:
Grease unable to form a stable oil film
Increased friction and wear
Chemical reactions when mixing incompatible greases
Dust contamination during lubrication
Best practices:
Use the correct grease type specified for the bearing
Never mix different greases
Thoroughly clean old grease before switching types
Keep grease storage sealed against moisture and dust
Inspect and clean lubrication pipelines regularly
3. Insufficient Cooling Capacity
Actions to take:
Check for pipeline blockages
Monitor inlet oil and return water temperatures
Replace undersized or inefficient coolers
Install additional coolers in parallel if necessary
Inspect axial-flow induced draft fans for proper sealing and insulation
4. Coupling Alignment Issues
Ensure coupling alignment meets technical standards
Account for thermal expansion during operation
For example:
Induced draft fan bearings rise due to thermal expansion
Fluid coupling temperature increase causes bearing housing expansion
Motors should be set slightly higher during alignment to compensate
The reserved alignment allowance depends on equipment characteristics and operating temperature conditions.
Key Points in Bearing Inspection
1. Bearing Condition Assessment
Check for:
Grease deterioration, agglomeration, or contamination
Seizure, abnormal wear, or surface damage
Cracks, rust, peeling, pitting, or discoloration
Excessive internal clearance
Bearings showing these defects should be replaced immediately.
2. Bearing Fit Inspection
Proper fit between:
Bearing inner ring and shaft
Bearing outer ring and housing
If the fit is too loose:
Creeping occurs
Wear debris enters the bearing
Heat, vibration, and damage increase
If the fit is too tight:
Bearing internal clearance decreases
Friction and temperature rise sharply
Bearing selection must consider:
Load characteristics
Size and operating temperature
Rotation of inner and outer rings
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