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      MILL SIZING EXPLAINATION          
      By the Bond method           
                 
    1 Work index (base) These data are normally defined in laboratory      
      SG Specific gravity of ore          
                 
    2 Efficiency factors          
                 
    2a EF1: Kind of process If dry process = 1,3        
        If wet process = 1        
                 
    2b EF2: Open circuit correction Required product in % Passing of Bond separation size in µ EF2      
        50 1,035      
        60 1,05      
        70 1,1      
        80 1,2      
        90 1,4      
        92 1,46      
        95 1,57      
        98 1,7      
                 
       
     
           
    2c EF3: Mill diameter correction           
                 
       
     
            
                 
       
     
           
                 
                  
    2d EF4: Feed size correction          
                 
                 
        where Wib is Work index base,      
        Pf is the 80% Passing dimension in the feed       
        Po is the 80% Passing dimension in the O'flow      
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         If Po < 75µ in wet process and 15µ ≤ Po ≤ 75µ,      
        then apply the correction factor      
       
     
           
    2e EF5: Product fineness correction          
                 
                 
        
     
           
    2f EF6: Reduction ratio correction   if Pf/Po < 6      
                 
                 
                 
                 
    3 Work index corrected
     
           
        where Wic = work index corrected      
                 
       
     
           
    4 Specific energy (estimated)          
                 
                 
    5 Production target Data defined by the plant      
                 
       
     
           
    6,7 Power required          
                 
        where P = power in kW,        
        Q = Production target in t/h and      
        σ = efficiency in %        
                  
    8 Mill diameter The mill diameter is calculated with a mill power formula.    
        Few formulas can be used at the discretion of the user.    
        The most famous being the Bond formula      
       
     
           
                 
                 
        where C = 1 if overflow mill and 1,16 if grate mill,      
        J =volume load in %,        
        Vcr = % of critical speed        
        Sg = bulk density of the ball charge in t/m3      
        L = mill length        
        Di = mill internal diameter      
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