Types

Belt scales differ in the type of control:

  • Check weigher scales
  • Dosing belt scales control the mass flow according to a predefined target value

Application of dosing belt scales

  • Continuous, gravimetric dosing of bulk materials (coarse, granular, flowable, brittle and not shooting materials)
  • Dispensing with an accuracy better than ± 1% over the setting range (at a measurement time of 60 s)
  • Fulfills high accuracy requirements for a feed rate of approx. 100 kg/h or higher

Advantages of dosing belt scales

  • High feed rate
  • Continuous material discharge from any large supplying silo
  • No mechanical influence on the material
  • Low mechanical design

Dosing belt scales

  • have a robust construction in a modular design
  • can be easily adapted to specific problem solutions
  • are driven by a gear motor with an operating range of 1:10 (1: 100)
  • weigh the material on the belt and simultaneously regulate the belt speed
  • ensure a constant flow of material

Performance table of our dosing belt scales

Type

Belt

speed

v

Belt

width

b

Nmax

(Volume)

Nmax

(γ =0.5 t/m3)

KDA-Z/280 0.2 m/s 150 mm 4 m3/h 2 t/h
KDA-Z/380 0.2 m/s 250 mm 10 m3/h 5 t/h
KDA-Z/400 0.2 m/s 250 mm 10 m3/h 5 t/h
KDA-Z/650 0.2 m/s 470 mm 40 m3/h 20 t/h
KDA-Z/850 0.2 m/s 650 mm 64 m3/h 32 t/h
KDA-Z/1100 0.2 m/s 800 mm 86 m3/h 43 t/h
KDA-Z/1500 0.2 m/s 1,200 mm 144 m3/h 72 t/h

 

v:       belt speed

b:       useful belt width

N:       dosing performance

γ:       bulk density

  bandwaage 400a gravametrical dosing

Belt Scale 1500
 

 

Operating mode of dosing belt scales

  • A conveyor belt feeds the material to the discharge station
  • A strain gauge load cell measures the mass flow of the belt over a defined lenght
  • The belt speed controls the mass flow by changing the motor speed

The mass flow controller of a dosing belt scale integrates two loops:

  • a volumetric control loop and
  • a gravimetric control loop

The first control loop regulates the speed of the belt scale:

  • The motor speed is controlled in proportion to the target value
  • A tachometer generator detects the motor speed
  • The controller compares the tacho-voltage with the target value and controls the motor accordingly

The second control loop governs the true dosing performance (belt speed x weight):

  • The controller compares the measured dosing performance to the target value
  • The difference is passed as a control variable to the motor controller for correcting the belt speed

At the start of the dosing belt scale initially the first control loop is active (volumetric mode). A few seconds delayed the second control loop takes over (gravimetric control).