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      Marked Ball Test                
                               
        1 Introduction:                  
          - Marked ball tests, abbreviation MBT, are performed both in cement and mining area.      
          - It is obviously admitted that they have much more importance in the field of mines where the wear is drastically higher.
          - Economic interest is more critical, whether for the mining people or the supplier of balls.      
          - However, these tests are also very useful in the cement field.          
          - It is important to note that some producers (cement and mining) make reservations about the merits of these tests.  
                               
        2 Goals of the MBT:                
          - A supplier wants to prove that his product is better.            
          - A cement producer wants to compare various suppliers for inclusion in the bendor list, for example.    
          - A supplier of grinding media and a mining/cement producer agree to realize a deep study in order to obtain the best ball quality.
                               
        3 Marked balls:                  
          - It is widely accepted that 200 balls are necessary and sufficient to do the test (200 balls for one quality of alloy).  
          - A hole is drilled in each ball.              
          - The hole has the following dimensions: diameter 5mm and 15mm deep.        
          - Example of marked ball:                
           
     
                   
          - If various qualities are tested, balls are marked as following:          
             
     
                 
                           
                           
            Quality 1 Single hole drilled from surface to center      
                           
                           
                           
                           
                           
            Quality 2 Two holes drilled in line 180°        
                           
                           
                           
                           
                           
            Quality 3 Two holes drilled in line 180°        
              and 3rd hole at 90° in the same plane        
                           
                           
                           
                           
            Quality 4 Four holes drilled at 90° in the same plane      
                           
                           
                           
                           
                           
            Quality 5 Four holes drilled at 90° in the same plane      
              and 5th hole to center in a perpendicular plane      
                           
                           
            etc...                  
          - One can also inject a colored resin in the holes.            
          - All the balls must be weighed.              
          - The balls weight tolerance should not vary more than ±2 grams.          
          - An average weight is then calculated for each quality of marked balls, it will be the initial weight of the marked ball test
            controls.                  
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        4 Controls procedure:                
          - Marked balls are introduced in the mill at the initial day of the test.        
          - In the cement area, the first control will be carried out after ±1000 hours of mill's operation.    
          - Concerning the mining area, the first control will be carried out after ±400 hours of mill's operation.    
            It depends of the wear rate existing figure.            
          - Generally, 6 controls are performed.              
          - The test can continue up to one year for a mill operating 2/3 of the time (16-17 hours per day).    
          - For a control to be valid and representative, more or less 15 balls of each quality must be find in the mill ball charge.  
                               
        5 Data to take during the test:              
          - Inspection date                
          - Hours of production between inspections            
          - Production of cement in t                
          - kwh at the beginning and at the end of the period             
          - Balls top up in kg                
          - Weight of each marked balls found inside the ball mill          
                               
        6 Results of the marked ball test:              
          - The following tables show us what results we get with the data collected during all the controls of the MBT:  
           
     
     
             
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        7 Example:                  
          - Remark: This example is completely fictitious            
           
     
                     
                               
                               
                               
        8 Important remark:                
            This presentation is based on the method developed by the Magotteaux company      
                               
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