Slewing Ring Selection

  1.Load Capacity of Slewing Ring

  Slewing ring shall commonly transmit axial load (Fa), radial load (Fr) and tilting moment (M) during working, combination of these three loads may vary due to different working ways of machines or structures. There is sometimes combination of two loads while sometimes only one exists.
Generally, there are two ways to install slewing rings: compressive installation and suspended installation. The loads of the slewing ring for each way are as follows:

  If the slewing ring is with compressive installation, the customer could select and calculate as follows; if the slewing ring is with suspended installation or other installation types, please contact R&D Department for assistance.

  2.Slewing Ring Selection

  2.1 Selection of structure    
There are four structures of slewing ring: single-row ball slewing ring, double-row ball slewing ring, cross-roller slewing ring, and triple-row roller slewing ring.
· Do ≤ 1800, single-row ball slewing ring is the preference;
· Do > 1800 or heavy loads where radial dimensions are restricted, double-row ball slewing ring is recommended. 

2.2 Calculation of slewing ring
2.2.1 Calculation of single-row ball slewing ring             
① Calculation of rated static capacity         
                                       C₀= 0.15×D_O×d₀
                                       C₀ —— Rated static capacity, kN            
                                       D₀ —— Diameter of raceway center, mm        
                                       d₀   —— Diameter of ball, mm       
②  Equivalent axial load calculation according to external compound loads       
                                       Cp = Fa + 4370M/D0+ 3.44Fr 
                                       Cp —— Equivalent axial load, kN      
                                       M  —— Tilting moment, kN·m                                            

                                       Fa —— Axial load, kN        
                                       Fr —— Radial load, kN       
③  Safety factor                              
                                       fs = C0 / Cp 
                                       fs refer to the following Table 1  

2.2.2  Calculation of double-row ball slewing ring             
① Calculation of rated static capacity         
                                      C₀= 0.28×D_O×d₀
                                      C₀——Rated static capacity, kN            
                                      D₀——Diameter of raceway center, mm        
                                      d₀——Diameter of ball, mm       
② Equivalent axial load calculation according to external compound loads        
                                       Cp = Fa + 4370M/D0+ 3.44Fr 
                                       Cp  ——Equivalent axial load, kN      
                                         M ——Tilting Moment, kN·m                                            

                                         Fa——Axial load, kN        
                                         Fr——Radial load, kN       
③ Safety factor                               
                                       fs = C0 / Cp 
fs refer to the following Table 1    
  

  2.3 Selection of product through static load curve
  Static load curve indicates the maximum loading of slewing ring in static. Each type of the slewing ring in the catalogue has a corresponding static load curve, which can help customer to make an elementary selection of slewing ring.
  2.3.1 Draw the static load curve 
  Customers draw the static load curve of the preferred slewing ring based on its  reference. See as follows:

 P1=Co
      M1=Co * Do/4370（Triple-row roller type: M1=Co * Do/4500）
 

 2.3.2  The intersection points of total axial load (Fa) and total tilting moment (M) multiply the safety factor respectively shall locate below the static load curve.

    2.3.3  Example: Draw the static load curve of QUA1000.32
       P1= Co= 0.15*1000*32= 4800kN
       M1= Co * Do/4370= 4800*1000/4370= 1098 kN·m  
    
Static load curve see as follows:

  .4 Calculation of slewing ring service life
 If a slewing ring service life calculation is required, the loads distribution of the machine needs providing.

2.5 Technical parameters of slewing ring selection
After the elementary selection of slewing ring, customer can verify it together with R&D Department or provide related information of the slewing ring for further calculation. When the selection is requested, please fill Data Collection Sheet for Selection to achieve an economical and suitable design.