Choosing the wrong clearance, will the bearing suffocate or fall apart?
Among the numerous technical parameters of bearings, there is a often overlooked but far-reaching "invisible role" - clearance. Although it is not conspicuous, it directly determines whether the equipment can operate smoothly and for a long time. Choosing too big, the machine shakes like a sieve; Choosing too small may cause the bearing to instantly 'heat up'. How should I choose?
1、 What is clearance? Don't be intimidated by the terminology
Simply put, clearance refers to the "gap" between the internal components of a bearing. Radial clearance: The movable distance in the diameter direction between the rolling element and the inner and outer rings. Axial clearance: The degree of tightness along the axis direction. Imagine: if it's too tight, the parts will generate heat due to friction and get stuck; Too loose, swaying during operation, loud noise, and poor accuracy. Appropriate clearance is like leaving "breathing space" for bearings.
2、 Scientific selection: bigger is not better, nor is smaller more stable
The selection of clearance should be based on comprehensive working conditions and cannot be a one size fits all approach. High temperature environment or interference fit (such as motor spindle): The expansion of the inner ring will compress the clearance, and C3 or C4 (larger clearance) should be selected to compensate for thermal expansion. High speed and high-precision equipment (such as precision machine tools): In order to reduce vibration, sometimes C2 (smaller clearance) is used to improve rigidity. In situations with large temperature differences and severe load fluctuations (such as metallurgical fans), C3 should be given priority, taking into account both thermal deformation and stability. One sentence: The clearance should be dynamically matched with the actual operating state, rather than static drawing parameters.
3、 Blood and tears lesson: The real cost of improper play
Case 1: A fan in a power plant frequently burned bearings, and upon disassembly and inspection, it was found that the inner ring was severely interlocked. reason? When designing, temperature rise was not considered and standard clearance (CN) was used. However, the actual clearance returned to zero at high temperatures, resulting in dry friction overheating.
Case 2: The conveyor belt reducer has severe abnormal noise and excessive vibration. After investigation, it was found that the C4 clearance was misused, causing the rolling elements to slip and the impact to intensify.
Preventive advice:
1. Review the fitting tolerance and working temperature before installation;
2. Conduct clearance testing on key equipment (using a feeler gauge or specialized tool);
3. Pay attention to the manufacturer's recommended clearance groups and do not blindly replace them.
