What are the precautions during the installation process of self-aligning roller bearings?

The installation quality of self-aligning roller bearings directly affects their operational accuracy, lifespan and equipment stability. The following are the precautions that must be strictly followed during the installation process, classified and explained according to the operation procedures and key points:
I. Preparations and Inspections before Installation
1. Environmental and component cleaning
Installation site: Keep the environment clean to prevent dust, metal debris and other impurities from entering the bearings. If necessary, wipe the workbench and tools with a lint-free cloth.
Component inspection:
Bearings: Visually inspect the raceways, rollers and cage surfaces for scratches, rust or deformation. When rotating the outer ring of the bearing, it should be smooth without jamming.
Shaft and seat hole: Use a micrometer to measure the dimensional tolerances of the shaft journal and seat hole (such as the cylindricity of the shaft journal ≤0.01mm), and use a roughness meter to detect the surface roughness (Ra of the shaft journal ≤1.6μm, Ra of the seat hole ≤3.2μm), to ensure compliance with the design requirements.
2. Preparation of tools and auxiliary materials
Special tools: press sleeve, hydraulic press, puller, heating equipment (such as oil bath pot), dial indicator and magnetic gauge base, etc. It is strictly forbidden to directly strike the bearing with a hammer.
Auxiliary materials: Clean kerosene, lint-free cloth, grease (for temporary lubrication during installation), rust inhibitor (if the components rust, they need to be treated in advance).
Ii. Core Precautions during the Installation Process
1. Selection of installation methods and force specifications
Cold mounting method (with a smaller interference fit) :
Use a dedicated pressure sleeve to evenly press the bearing into the journal. The end face of the pressure sleeve must be perpendicular to the shaft to ensure that either the inner ring is subjected to force (when installing the inner ring) or the outer ring is subjected to force (when installing the outer ring), and avoid force acting on the cage or rollers.
When installing the inner ring, press the sleeve against the end face of the inner ring and apply pressure slowly through a hydraulic press until the bearing is in place.
Hot mounting method (with a large interference fit) :
Place the bearing in an oil bath and heat it to 80-120℃ (do not exceed 120℃ to prevent annealing). After taking it out, quickly put it on the journal. Be sure to wear heat-insulating gloves to avoid burns.
When heating, the bearing should be suspended in the oil to avoid touching the bottom of the pot and causing local overheating.
Prohibited behavior: It is strictly forbidden to strike the outer or inner ring of the bearing with a hammer to prevent deformation of the raceway or breakage of the rollers.
2. Fit accuracy and clearance control
Interference fit: Control the interference fit as per the design requirements (for example, under light load conditions, the interference fit is 0.01 to 0.03mm; under heavy load, it is 0.03 to 0.05mm). An excessive interference fit may cause the inner ring to expand and the clearance to decrease; if it is too small, it is prone to slippage and wear.
Clearance adjustment: After installation, use a feeler gauge or a clearance measuring instrument to check the bearing clearance to ensure it meets the working condition requirements (for example, C3 clearance is suitable for high-temperature or high-speed scenarios). If necessary, adjust the position of the bearing housing through a gasket or use a pre-tightening device (such as a spring).
3. Centering and coaxial calibration
Although self-aligning roller bearings have self-aligning function (allowing shaft deviation ≤1.5°), excessive deviation will lead to uneven load distribution and accelerate wear.
Calibration method:
Fix the dial indicator on the shaft and rotate the shaft to measure the coaxiality of the seat hole (allowable deviation ≤0.05mm).
For long shaft systems, the coaxiality of multiple bearing housings can be calibrated by a laser alignment instrument to ensure that the axis deviation is within the allowable range.
Iii. Inspection and Trial Operation after Installation
1. Installation status check
Axial and radial clearance: Use a dial indicator to press against the outer ring of the bearing, push the bearing axially/radially, and measure the displacement (axial clearance ≤0.1mm, radial clearance is judged according to the clearance standard).
Fit tightness: Tap the outer ring of the bearing and listen to the sound to determine if it is too loose (if it is loose, the sound will be muffled). If it is too loose, reinstallation or replacement of components is required.
2. Trial operation monitoring
No-load operation: Start the equipment and let it idle for 10 to 15 minutes. Use an infrared thermometer to monitor the bearing temperature (a temperature rise of ≤20℃ is normal), and listen for the operating noise with a stethoscope (it should be uniform with no abnormal noise).
Load operation: Gradually load to the rated load, and check the temperature (maximum ≤80℃), vibration (speed ≤4.5mm/s) and noise again. If any abnormality is found, stop the machine immediately for inspection (such as sudden temperature rise or sharp abnormal noise).
Iv. Key Points for Installation under Special Working Conditions
1. High-temperature environment
When installing, reserve a larger thermal expansion clearance (such as choosing C4 clearance) to prevent the clearance from disappearing and the bearing from seizing due to temperature rise during operation.
During hot mounting, control the heating temperature (≤100℃) to prevent the performance of the bearing material from deteriorating.
2. Heavy load or impact working conditions
Before installation, check the strength of the journal and the seat hole. If necessary, increase the support stiffness (such as thickening the bearing housing) to avoid deformation under force.
When an interference fit is adopted, the interference amount should be appropriately increased (such as 0.05 to 0.08mm) to prevent relative sliding between the bearing and the shaft.
3. Vertical installation (vertical shaft)
A thrust device (such as a positioning ring) needs to be installed above the bearing to prevent axial movement due to gravity.
When using oil lubrication, ensure that the oil passage is unobstructed and avoid insufficient lubrication due to vertical installation.
V. Installation Taboos and Common Error Avoidance
Error 1: Mixing bearings of different precision grades with shaft/seat holes (for example, a P6 grade bearing with a journal processing accuracy of only IT8) leads to fit failure, and strict matching in accordance with tolerance standards is required.
Error 2: During installation, the burrs or rust on the journal were not cleaned, resulting in scratches on the inner ring of the bearing. Before installation, it needs to be sanded with sandpaper and wiped clean.
Error 3: Uneven application of grease or the use of substandard grease may cause local dry friction during operation. It is necessary to select grease that matches the working conditions (such as extreme pressure lithium-based grease) and apply it evenly to the raceway.
Summary
The installation of self-aligning roller bearings should follow the principles of "cleanliness, precision and uniform force distribution". A standardized process should be formed from environmental preparation, component inspection to installation methods and precision calibration. Special attention should be paid to fit tolerances, coaxiality and lubrication pretreatment. After installation, the status is verified through trial operation monitoring to prevent early failure due to improper operation and lay a foundation for the long-term stable operation of the bearing.