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Centrifugal pumps rely heavily on the proper functioning of their bearings to ensure smooth operation and long service life. Bearings can be either rolling or sliding types, each with specific installation, maintenance, and repair requirements. Understanding these techniques is essential for engineers and technicians working with centrifugal pumps.
**Rolling Bearings**
1. The fit between the bearing and the shaft follows the base hole system, while the fit between the bearing and the housing uses the base shaft system. The precision of rotation and bearing dimensions must comply with GB307-84 standards.
2. The journal and inner bore of the bearing should conform to GB1031-83 specifications. The surface roughness (Ra) of the journal should be less than 1.6 μm, while that of the housing bore should be less than 2.5 μm.
3. When manufacturing bearing rings and rollers from GCr15 or ZGCr15 steel, the hardness should be 61–65 HRC. For GCr15SiMn or ZGCr15SiMn, it should be 60–64 HRC. Hardness uniformity and testing methods must follow JB1255 guidelines.
4. Radial and axial clearances must meet GB4604-84 standards to ensure smooth operation and reduce wear.
5. The raceways of the inner and outer rings should be free from chipping, severe wear, or cracks. Balls should not show signs of wear, and cages should remain intact without deformation. Any abnormal noise or vibration during rotation indicates potential issues.
6. For C-class tapered roller bearings, the contact accuracy between the roller and raceway should be checked under load. Using color marking, the contact area should be continuous, with a minimum length of 80% of the roller’s length.
**Sliding Bearings**
1. For radial thick-walled bearings, the clearance and interference fit should be measured using the lead wire method or other appropriate techniques. The clearance should meet the required specifications, and the tile shell interference should be between 0 and 0.02 mm.
2. Inspect all components for damage, cracks, or defects. The bearing bush should not have peeling, pores, cracks, or localized wear.
3. The contact between the bearing bush and the journal should be checked using the color method. The contact angle should be between 60° and 90°, depending on the rotational speed. A minimum of 2–4 contact points per square centimeter is required. If the contact is poor, scraping may be necessary.
4. Clean the bearing housing thoroughly, ensuring all oil holes are clear and free from cracks or leaks.
5. The back and housing should fit tightly and evenly. Using the color method, the contact area should be at least 50%.
For radial thin-walled bearings:
1. The alloy layer and the tile shell must be firmly bonded without delamination or peeling. The surface should be flat, lubricated, and free from cracks, pores, or inclusions.
2. The back of the bearing and the inner bore of the housing should fit closely and evenly. For inner diameters less than 180mm, the contact area should be at least 85%. For larger sizes, it should be at least 70%.
3. The contact between the bearing bush and the journal should be ensured through machining precision. Scraping is generally not allowed unless there is uneven contact along the axial direction.
4. After installation, a 0.02mm feeler gauge should not pass through the joint.
For thrust bearings:
1. The bearing bush should be free from wear, deformation, cracks, scratches, or burn marks. The contact area should be at least 70%, with even distribution across the entire circumference. The thickness difference among tiles in the same group should not exceed 0.01mm. The babbitt layer should be shaped into an oil wedge to facilitate lubrication, and the back should be flat and well-lubricated.
2. Adjusting shims should be flat, non-deformable, and have a thickness difference of no more than 0.01mm.
3. After assembly, the thrust clearance should be measured using the push shaft method, and the value should fall within the acceptable range. Proper alignment of the displacement probe is also crucial.
4. The horizontal contact surface of the bearing shell should be tight and properly positioned. Oil temperature measuring holes and tile cover eyes should align correctly without any misalignment. Ensure the oil holes are clean and unobstructed.
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**Related Bearing Knowledge**
- Bearing Installation Techniques
- Heat Treatment Processes for Bearings
- Diagnosing and Addressing Bearing Noise
- Common Bearing Failures and Their Solutions
This article was originally published on China Bearing Network.
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Analyze and repair the skills and usage of centrifugal pump bearings
Source: Bearing Network | Date: January 9, 2014