Bearings, as critical components in mechanical equipment, have their installation quality directly impacting the operational accuracy, stability, and service life of the equipment. However, due to negligence or improper operation during installation, bearings often fail prematurely, even leading to equipment malfunctions. This article will analyze in detail the causes and consequences of various bearing installation errors through multiple examples, and provide correct installation methods and techniques to help readers learn early and avoid mistakes.
1. Inner Ring Slip
“Inner ring slip” refers to a loose fit between the shaft and the bearing bore, causing sliding between their surfaces. This sliding friction generates significant heat, damaging the bearing due to overheating. Specific manifestations include cracks on the end face of the inner ring where it rubs against the shoulder of the shaft. The continuous extension of these thermal cracks can lead to the fracture of the inner ring during use. Additionally, sliding friction can melt the surface metal and cause adhesion, further exacerbating bearing damage.
2. Outer Ring Slip
Similar to “inner ring slip,” “outer ring slip” occurs when there is a loose fit between the housing bore and the bearing outer diameter, resulting in sliding between their surfaces. The sliding friction also induces heat, causing bearing damage. Evidence of “outer ring slip” can be seen in the sliding marks on the surfaces of the housing bore and the bearing outer diameter.
3. Direct Hammering on the Bearing
When installing bearings with an interference fit between the inner ring (or outer ring) and the mating part, it is strictly prohibited to directly hammer on the end face of the inner ring (or outer ring) with a hammer. This operation can easily damage the rib, leading to bearing failure. The correct installation method is to use a sleeve placed on the end face of the inner ring (or outer ring) and hammer on the sleeve to install the bearing. Furthermore, when installing bearings with an interference fit on the inner ring, force should not be transmitted to the inner ring through the outer ring and rolling elements, as this can damage the raceway and rolling element surfaces, causing noise and early bearing failure during operation.
4. Excessive Heating Temperature
Some users, for the sake of convenience during installation, use an acetylene torch to heat the inner bore of the bearing. However, when the heating temperature exceeds 727°C (the phase transformation temperature of bearing steel), the metallographic structure inside the bearing steel changes. After the bearing cools down, the inner bore cannot return to its original size and is usually larger than before heating. This not only results in a loose fit but also affects the bearing’s performance and service life.
5. Improper Installation Leading to One-Sided Loading
During installation, if the bearing is not installed properly or the force is not evenly distributed, it can lead to one-sided loading on the bearing. For example, in a self-aligning roller bearing, if one row of rollers is loaded while the other row is not, it can damage the inner and outer raceways and one row of rollers. This is often caused by improper use of installation tools or incorrect installation methods.
6. Neglecting Cleanliness of the Installation Environment
Bearings are high-precision parts that require a high level of cleanliness in the installation environment. If the cleanliness is neglected during installation, and the bearing is contaminated by oil, impurities, etc., it can result in stiffness, noise, and vibration during bearing operation. Therefore, bearing installation should be carried out in a dry, dust-free area, away from equipment that generates metal debris and dust.
Correct Installation Methods and Techniques
To avoid the aforementioned installation errors and ensure the normal operation and extended service life of bearings, the following are some correct installation methods and techniques:
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Check the Integrity of Bearings and Related Components: Before installation, carefully inspect the bearings and related components for any damage, cracks, or defects.
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Clean the Bearings and Installation Areas: Clean the bearings and installation areas before installation to remove oil, impurities, etc., ensuring a clean installation environment.
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Choose Appropriate Installation Methods: Select the appropriate installation method based on the type and size of the bearing. For small bearings with a not-too-tight fit, they can be gently tapped into place using a sleeve and a hammer. For the installation of larger bearings, methods such as heating or hydraulic pressure are usually required.
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Uniformly Heat the Bearings: If the heating method is used for installation, ensure uniform heating to avoid localized overheating. The heating temperature for open bearings should not exceed 120°C, and for bearings with seals and dust covers, the temperature should not exceed 80°C (ensuring that the temperature does not exceed the allowable temperature for seals and grease).
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Pay Attention to Alignment and Flatness During Installation: Ensure the alignment and flatness of the bearing with the shaft or bearing housing during installation. If the bearing housing is not installed flat, it needs to be readjusted or shimmed for compensation.
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Tighten Fixing Screws: After installation, check and tighten the fixing screws to ensure they meet the required torque. For looseness due to damaged threads, replace the screws with new ones.
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Maintain Good Sealing and Lubrication: Bearings should have good sealing and dust-proof devices and lubrication conditions during use, and should not be operated without lubrication. Regularly check the working condition of the bearings, replace damaged seals, and replenish grease as needed.
