Bearing Installation, Maintenance and Fault Diagnosis Q&A

1. What preparations are needed before bearing installation?
Pre-installation preparations directly affect bearing service life, and the following points should be done: ① Cleaning: thoroughly clean the surfaces of matching components such as shafts, bearing housings, and end caps to remove oil stains, rust, burrs, and dust, avoiding foreign matter wear after installation; ② Precision inspection: confirm that the fit size, roundness, and cylindricity of shafts and bearing housings meet requirements without deformation or damage; ③ Prepare suitable tools: use special installation tools (such as sleeves, presses) to avoid directly striking bearings with hammers, preventing damage to rolling elements and raceways; ④ Apply an appropriate amount of suitable grease/oil inside the bearing or on the matching surface in advance according to the lubrication method.

2. What are the common installation methods for bearings with interference fit?

Interference fit (tight fit between inner ring and shaft, outer ring and bearing housing without clearance) requires heating or pressing to avoid hard hitting: ① Hot fitting method: suitable for inner ring interference fit, heat the bearing in an oil bath to 80-100℃ (not exceeding 120℃ to prevent changes in bearing steel performance), quickly sleeve it on the journal after heating, and the bearing will fit closely with the shaft after cooling; preheat the journal before installation to avoid cracks caused by rapid cooling of the bearing due to excessive temperature difference; ② Cold pressing method: suitable for small and light bearings, use a press to smoothly press the bearing into the shaft or bearing housing through a sleeve, ensuring the sleeve fits the end face of the bearing inner/outer ring for uniform force transmission and avoiding local damage.

3. What are the possible fault causes and solutions for excessive bearing temperature during operation?

The normal operating temperature of bearings generally does not exceed 70℃. Excessive temperature is mostly caused by the following reasons: ① Abnormal lubrication: excessive/insufficient, mismatched, or deteriorated grease/oil; solution: clean old lubricant, supplement suitable grease/oil according to standards to ensure sufficient and non-redundant lubrication; ② Over-tight installation: too small fit clearance, increasing friction during operation; solution: recheck fit size, adjust clearance, and replace suitable bearings or process components if necessary; ③ Foreign matter intrusion or wear: internal impurities or wear of rolling elements/raceways; solution: disassemble the bearing to clean foreign matter, replace with new bearing if severely worn; ④ Overload: exceeding the rated bearing load; solution: optimize mechanical structure, reduce load, or replace with bearings with higher rated load.

4. What is the function of a bearing sealing device? What are the common types?

The core function of a sealing device is to prevent leakage of grease/oil inside the bearing and block external dust, moisture, and impurities from entering, ensuring bearing lubrication effect and operating environment. Common types are divided into contact seals and non-contact seals: contact seals (good sealing effect, suitable for low-speed scenarios), such as felt ring seals and lip seal ring seals; non-contact seals (no friction wear, suitable for high-speed scenarios), such as gap seals, labyrinth seals, and oil slinger seals. The appropriate type can be selected according to rotation speed and working conditions (dust and water resistance requirements) in practical applications.

5. How to judge whether a bearing needs to be replaced?

Bearings should be replaced in a timely manner when the following situations occur: ① Abnormal noise and vibration increase significantly during operation, which cannot be solved by lubrication or adjusting installation position, indicating internal component wear or damage; ② Bearing temperature remains too high (exceeding 70℃) accompanied by odor (grease deterioration), with no improvement after excluding other faults; ③ Pitting, spalling, cracks, deformation on rolling elements/raceways, or damaged cage, severe rust on inner/outer rings observed after disassembly; ④ Bearing clearance exceeds the allowable range, obvious shaking during rotation, failing to ensure positioning accuracy and affecting normal mechanical operation.

6. How to select bearing grease under different working conditions?

Grease selection should match working conditions, rotation speed, temperature, and load: ① Low-speed, heavy-load conditions (such as crane bearings, crusher bearings): select grease with small penetration and high consistency, such as lithium-based grease and calcium-based grease, to improve load-bearing capacity; ② High-speed, high-temperature conditions (such as machine tool spindles, motor bearings): select grease with large penetration and high temperature resistance, such as synthetic lithium-based grease and polyurea-based grease, to reduce friction heat generation; ③ Humid, dusty conditions (such as outdoor machinery, water pump bearings): select grease with good water resistance and rust prevention, such as calcium-sodium-based grease, to prevent rust caused by moisture intrusion; ④ Food, pharmaceutical industry conditions: select food-grade standard grease to avoid product contamination.