Choosing the right slewing bearing for a crane requires comprehensive consideration of working conditions, performance parameters, and other factors. Here are the key points:
• Crane type: Determine the bearing load requirements based on the crane type (e.g., tower crane, truck crane, wheeled crane, etc.). For example:
◦ Double-row ball slewing bearings are suitable for small and medium-sized tower cranes and truck cranes, as they can withstand large axial forces and overturning moments.
◦ Triple-row roller slewing bearings are preferred for heavy-duty wheeled cranes and large-tonnage equipment, as they have the strongest load-carrying capacity.
• Working environment: Consider factors such as temperature, humidity, and dust. For humid or corrosive environments, use corrosion-resistant materials (e.g., stainless steel outer rings) or enhanced sealing designs (nitrile rubber seals).
• Load types: Clearly define the specific values of axial force, radial force, and overturning moment that the bearing will bear, which can be obtained through crane design parameters or mechanical calculations.
◦ Single-row four-point contact ball bearings: Suitable for scenarios with relatively small combined loads of axial force, radial force, and overturning moment (e.g., small and medium-sized equipment).
◦ Single-row crossed roller bearings: Can withstand large radial forces and overturning moments, suitable for medium-sized cranes.
• Speed and precision: If the crane has a high rotation speed (e.g., frequent slewing operations), select bearings with low rolling element friction coefficients and high precision grades (e.g., P5 precision).
• Structure type: Match the bearing type according to load requirements (refer to the characteristics mentioned above). For compact designs, single-row four-point contact ball bearings are optional; for high rigidity, crossed roller bearings are selected.
◦ Diameter: Determined according to the crane turntable diameter and installation space, and the outer diameter of the bearing should match the turntable connection size.
◦ Mounting holes: Check whether the number and spacing of bearing mounting holes are consistent with the main engine base to avoid installation misalignment.
• Raceway material: 50Mn steel is usually used. For heavy loads or impact working conditions, 42CrMo (high strength) can be selected. Ensure surface quenching hardness (HRC58-62) to improve wear resistance.
• Rolling elements and cages: Rolling elements are made of GCr15 bearing steel, and cages are made of polyamide (wear-resistant, low-noise) or aluminum alloy (lightweight).
• Sealing and lubrication: Oil-resistant rubber is selected for sealing rings to prevent dust and moisture from entering; the lubrication system should match the working conditions (e.g., lithium-based grease is used in high-temperature environments).
• Priority is given to well-known brands such as LTZC to ensure that products meet ISO/GB bearing standards, with material reports and load test data attached.
• Check the bearing appearance: no cracks or rust on the surface, flexible rotation of rolling elements, and no jamming or abnormal noise.
• Cost balance: Triple-row roller bearings have strong load-carrying capacity but high cost. For small and medium-sized equipment, more cost-effective double-row ball or crossed roller bearings can be used.
• Maintenance design: Select bearings with oil injection holes and detachable sealing structures to reduce later maintenance difficulty (e.g., regular lubrication and replacement of sealing rings).
1. Determine the crane type, load parameters, and working environment;
2. Match the bearing structure type (four-point contact ball type/crossed roller type/triple-row roller type, etc.)
3. Check the size, material, and sealing lubrication requirements;
4. Refer to brand qualifications and test reports to ensure reliability;
5. Complete the selection by comprehensively considering cost and maintenance needs.
If there are specific crane models or working condition parameters, the selection plan can be further refined.
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