Modelling Conveyors in a Spread-sheet


In-pit crushing and conveying is an alternative materials handling system to the use of trucks in open pits.

Figure 1 presents a worked example of a conveyor calculation.

Table 1 A conveyor model example

Conveyor belt calculationsValueUnitsComment
Conveyor capacity10,000tphrDry metric tonnes
Conveyor speed4.0m/s 
Insitu density2.80t/m^3 
Swell factor150%  
Moisture content10%  
Belt width2.12m 
Belt weight per metre127kg/m 
Conveyor length 100m  
Conveyor grade10.0%  
Transfer drop3m 
Conveyor resistance3% Typical design factor
Gearbox efficiency90% Typical design factor
Motor electrical efficiency87.7% Typical design factor
Input power646kw 
Installed power711kw110% of electrical power

The formulas used in the spread-sheet were derived from the "Mechanics of bulk materials handling" by Norman Brooks.

Brook suggests:

  Conveyor width                  2.1 m    =(11*ConveyorCapacity*(1+MoistureContent)/3600*SwellFactor/InsituDensity/ConveyorSpeed)^0.5																			
  Conveyor belt unit weight       127 kg/m =60*BeltWidth																			
  Conveyor efficiency              3%      =3% to 4%																			

Conveyor power calculations:

  Power for empty conveyor         38 kw   =(BeltUnitWeight*2*ConveyorLength*(1+ConveyorGrade^2)^0.5*ConveyorResistance*ConveyorSpeed)*9.81/GearBoxEfficiency/MotorElectricalEfficiency/1000																			
  Power for conveyor load         114 kw   =(ConveyorCapacity*(1+MoistureContent)/ConveyorSpeed/3.6*ConveyorLength*(1+ConveyorGrade^2)^0.5*ConveyorResistance*ConveyorSpeed)*9.81/GearBoxEfficiency/MotorElectricalEfficiency/1000																			
  Power for conveyor lift/fall    494 kw   =((TransferDrop+ConveyorLength*ConveyorGrade)*ConveyorCapacity*(1+MoistureContent)/3.6)*9.81/GearBoxEfficiency/MotorElectricalEfficiency/1000																			
  Total input power               646 kw   =PowerForEmptyConveyor+PowerForConveyorLoad+PowerForConveyorLiftOrFall																			
  Installed power                 711 kw   =110%*TotalInputPower																			

If you would like a copy of the spread-sheet used above, click the link (Conveyors.xlsx).

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