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Since this occurs when the vacuum pump is operating at high speeds, an excessive rotor speed can cause the bearings that support the rotor to overheat. Generally, the following are the reasons for bearing overheating during the operation of a vacuum pump. 1. Valve disc crack: When a valve disc cracks, the pressures on both sides of the impeller become unbalanced, which generates an axial force on the rotor and increases the load on the bearings; prolonged operation can lead to an increase in the temperature of these bearings. In this case, the valve disc should be replaced promptly. Failure of the 2-axis end seal: When the packing in the shaft end seal is damaged or the seal water channels become blocked, air can be drawn into the pump through these damaged gaps, which affects the pump’s suction and exhaust performance. If only one side of the seal fails, an imbalance in pressure on both sides of the impeller will occur, generating an axial force on the rotor, which increases the load on the bearings and thus raises their temperature. 3. Excessive bearing preload: This condition leads to a reduction in the bearing clearance or even the elimination of such clearance, resulting in an increase in the bearing’s temperature. 4. Shock effects: When there is significant shock in the pump body or bearings, excessive bearing temperatures can occur. By examining the pump body to identify the cause of the shock and eliminating it, the bearing temperatures will return to normal. 5 Smooth surface condition: An excessive or insufficient amount of lubricant, an inappropriate type of lubricant, prolonged use of the lubricant, or contamination of the lubricant can all cause the bearing to overheat. At this point, it is necessary to check the type of lubricant, inquire with the manufacturer about the appropriate dosage, and adjust the lubricant accordingly to bring the bearing temperature back to normal. 5 Bearing damage: Damage to the bearing rolling elements and the bearing cage can both lead to symptoms of bearing overheating. If a bearing is damaged, it is necessary to replace it with a new one promptly.