Cai Hongbin
First check the packaging, the quality of the packaging box, and whether the packaging is regular. Check the printing later to see if the fonts are clear and whether the barcode printing is blurry. Under normal circumstances, brands produced by regular manufacturers have their own dedicated designers to design the outer packaging, and arrange factories with qualified production conditions for production. Therefore, the product packaging should be very clear and unambiguous, from lines to color blocks.
Each bearing product will have its brand name, label, etc. printed on the bearing product body. Although the font is very small, products produced by regular manufacturers all use steel stamping technology.
Remove the bearing packaging bag. Check if there are any turbid oil stains on the surface. Since there is still a certain gap between the current anti-rust technology in China and advanced foreign manufacturing countries, thick oil stains are easily left when anti-rust treatment is performed on the bearing body, which feels sticky when touched by hand. There is almost no trace of anti-rust oil on the imported bearings. According to industry insiders, particularly careful people can smell a special smell on imported bearings, which is the smell of anti-rust oil.
Also inspect the bearing carefully for dirt and rust. On visual examination, the inner and outer raceways should have no spalling or severe wear and should form continuous curved grooves. All rolling-element surfaces should be free of spots, cracks and peeling. The cage should not be loose, damaged or worn through, and its clearance to the rolling elements should not be excessive. The stated normal clearance between the inner and outer rings and rolling elements is 0.005–0.010 mm. Hold the inner ring with the left hand, turn the outer ring with the right and listen for abnormal operating noise.
Therefore, when the bearing rotates, there will be noise or uneven operation. For rolling bearings that have been used for a period of time, there should be no obvious shaking sound when holding the inner race with your fingers and shaking it axially. Hold the inner race of the bearing with one hand and rotate the outer race with the other hand. The bearing should be able to rotate flexibly and no radial shaking should be felt. For tapered roller bearings, it should also be observed whether the rolling element is located in the middle of the outer race. If there is any forward movement, it should not exceed 1.5 mm.
When the inner ring is held in one hand and the outer ring is given a quick, gentle push with the other, rotation should be smooth, with only a slight sound of balls rolling along the raceways and no vibration. As it stops, it should slow gradually without reversing afterward. In a normal radial ball bearing, clearance between the inner and outer rings and rolling elements is 0.005–0.010 mm. No clearance should be perceptible when the inner and outer rings are rocked radially. For a used bearing, hold the inner ring and shake it axially several times. If the outer ring and balls make an obvious noise, the fitting clearance exceeds 0.03 mm and the bearing should no longer be used.
After all inspections are completed, it can be installed and used by oil heating or bearing heater heating.
Source: Mechanical and Electrical Maintenance
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