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      Volume Load Measurement Explanation        
                             
      1    Introduction:                
          - The volume load is also called the filling degree and is always expressed in %.    
          - The measurement of the mill's volume load is a basic operation of the maintenance department.  
          - There are three typical ways to realize this measurement:        
            1. The measurement of the height between the top of the charge and the lining.    
            2. Count the number of visible lining plates on the diameter.        
            3. The measurement of the central screen (or inlet trunnion) and the distance between the top of the  
            central screen and the top of the charge.          
          - The three methods are developed below.          
      2    Measurement of H:              
          - One measures H because the calculation is made with the H/D ratio. D being the internal diameter of the mill
            and is supposed to be known.            
          - The measurement is easy to do except for large diameters (higher than 3,5m) because H is higher than 2,2m.
           
     
           
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
          - In this case, many people adopt a handmade template that allows a very reliable measure.  
          - On the side of the lining, the exact point where to put the meter is the average height of the plate, as shown
            in the sketch below:              
           
     
         
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
          - Obviously, the measurement is made on the mill axis and in 2 or three points depending of the mill  
            configuration:              
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          - Formulas used to calculate the volume load:          
           
     
       
               
               
               
            Where VL is the volume load in %,            
            and R is the internal mill radius in m            
          - Table showing the filling degree as a function of H/D:        
           
     
       
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
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      3    Counting of the number of visible plates of lining:        
          - The total number of lining plates of the perimeter of the diameter is supposed to be known.  
          - In a DIN configuration, it is very easy. A mill of 3,4 m diameter will has 34 plates on the perimeter whilst
            a 4,8 m diameter mill will have 48 plates.          
          - Formulas used to calculate the volume load with this method:        
           
     
                 
                         
                         
            Where θ is the angle shown on the figure below and expressed in radian.      
            To convert degrees in radians, please use the following formula:      
           
     
                 
                         
                         
            n is the number of visible plates and            
            N is the total number of plates.            
           
     
             
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
           
     
               
                       
                       
          - Table showing the filling degree as a function of the angle:        
           
     
       
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
          - This method is generally less accurate.          
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      4    Measurement of the central part and its distance to the top of the balls:    
          - This method can be also used but there are only 2 points of measurements for each compartments.  
          - The probability to get a incorrect measurement is more important.      
          - If the measurement is well done, this method gives realistic results.      
          - Examples of measurements:            
           
     
     
             
             
             
             
             
             
             
             
           
     
       
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
          - H is known with the following formula:          
           
     
                 
                         
                         
      5    Calculators:                
          - Nine calculators are available.            
          - For monochamber mill, 2 chambers mill and 3 chambers mill.        
          - For the three methods.              
            Calculators are available here:            
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