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        Screw conveyor
           
      4   Design elements (1st method) - suite
         4.4 Power calculation (suite)
         4.4.2 Power to move the material
        - The formula is as follows (derived from the formula in US units):
         
     
          With:
          Pm = power to move the material in kW
          Q = volumetric flow rate in m3/h
          L = screw length in meter
          ρ = material bulk density in kg/m3
          Fm = factor related to material (see 4.2 above)
          Ff = factor related to the design of the screw (flight factor) that we consider standard here, so Ff = 1
          Fp = paddle factor, when required, that is not the case here, then Fp = 1
        - If we replace the m3/h flow rate in t/h and considering the correction factors, we have:
         
     
          With:
          C = output in t/h
         4.4.3 Total absorbed power
        - The formula is the following:
         
     
          With:
          Pt = total absorbed power in kW
          Fo = factor related to the sum of the two powers (Pv + Pm):
         
     
          The above formula is empirical.
          Important notice: if (Pv + Pm) > 5,2 then Fo = 1
          e = engine and transmission efficiency (for example gearmotor: 0.94)
         4.4.4 Example
        - Data:
          * Material: Cement
          * Output: 50 t / h
          * Bulk density material: 1,1 t/m3
          * Screw length: 8 m
        - Calculation:
          * Volumetric flowrate = 50/1,1 = 45,5 m3/h
          * Screw diameter and speed will be according to Table 4.3: 457mm and 45 t/min max.
         
     
         
     
         
     
         
     
         
     
      5   Design elements (2nd method)
         5.1 Determination of the diameter
        - In this case, we propose a speed of rotation of the screw.
        - We only consider a horizontal conveyor.
        - The formula for determining the diameter is:
         
     
          With:
          D = Diameter of the screw in m
          C = Output in t/h
          γ = filling coefficient according to the table below:
         
     
         5.2 Power calculation
         5.2.1 Power to run an empty conveyor
        - The formula is as follows:
         
     
          With:
          Pv = unload power in kW
          L = screw length in meter
          D = screw diameter in meter
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         5.2.2 Power to move the material
        - The formula is as follows:
         
     
          With:
          Pm = power to move the material in kW
          C = Output in t/h
          L = screw length in meter
          g = 9,81 m/sec²
          Fr = material resistance coefficient according to the table:
         
     
         5.2.3 Total absorbed power
        - The formula is the following:
         
     
          With:
          Pt = total absorbed power in kW
          e = engine and transmission efficiency (for example gearmotor: 0.94)
         5.3 Example
        - Let us take the same data as above:
        - Data:
          * Material: Cement
          * Output: 50 t / h
          * Bulk density material: 1,1 t/m3
          * Screw length: 8 m
        - Determination of the diameter:
          * Let's consider a rotation speed of 45 rpm
          * Diameter:
         
     
        - Power calculation:
         
     
         
     
         
     
           
      6   References
        - Carlos III University - Mechanical Engineering Department
        - Thomas conveyor company
        - www.conveyoreng.com - Screw Conveyor components & design Version 2.20
        - Wam inc. - SCREW CONVEYORS Engineering Guide & Parts Catalogue
        - KWS MANUFACTURING COMPANY, LTD. - SCREW CONVEYOR AND BUCKET ELEVATOR ENGINEERING GUIDE
           
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