The limit speed of a FAG bearing is a limit value that does not cause frictional heating that causes burns and can be continuously rotated. FAG bearing limit speed is affected by FAG bearing size, type, lubrication, accuracy, oil gap, load and other factors, but the most important is the effect of lubricant and ambient temperature. At high speeds, especially when the speed is close to or exceeds the limit speeds stated in the dimension table, the following should be noted:
(1) use high precision FAG bearings;
(2) Analyze the internal clearance of the FAG bearing, and consider the reduction of the internal clearance of the FAG bearing caused by the temperature rise;
(3) Analyze the lubrication method. Lubrication methods such as cycle lubrication, jet lubrication, oil mist lubrication and oil and gas lubrication for high-speed rotation are adopted.
(4) Analyze the type of material of the cage. For high speed rotation, it is suitable to cut the cage with copper alloy or phenolic resin. There are also synthetic resin molded cages suitable for high-speed rotation;
For small machines, you can rotate by hand to confirm that the rotation is smooth. Inspection items include:
1. Whether there is any poor operation caused by foreign objects, scars and indentations;
2. Whether the torque generated by the poor processing of the mounting seat is unstable due to poor installation;
3. Whether there is excessive torque caused by too small clearance, installation error, sealing friction, etc.
If there is no above abnormality, you can start the power running.
However, it cannot be rotated manually for large machines. Therefore, immediately after the no-load start, the power is cut off, the machine is idling, and the presence or absence of vibration, noise, and whether the rotating parts are in contact with each other is checked. After confirming that there is no abnormality, the power is turned on.
The power running is started from the low speed at no load and slowly increases to the rated operation of the specified conditions. Check items during the test run include: abnormal sound, FAG bearing temperature change, lubricant leakage or discoloration, etc. If an abnormality is found, stop the operation immediately, check the machine, and remove the bearing check if necessary.
FAG bearing temperature check. Usually based on the external temperature of the housing. However, it is more accurate to directly measure the temperature of the outer ring of the bearing by using the oil hole. The temperature of the FAG bearing gradually increases from the start of the operation, and the temperature is usually stable after 1 to 2 hours.
If the FAG bearing is poorly installed, the temperature will rise sharply and an abnormally high temperature will occur. The reasons are such as excessive lubricant, too small bearing clearance, poor installation, excessive friction of the sealing device, and the like. In the case of high-speed rotation, the FAG bearing structure and the selection of the lubrication method are also the reasons.
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