Conveying and Sieving

The functionality and choice of the external vibrators at the conveying and sieving is identical and therefore is looked at together also. The external vibrator is only used differently at sieving. At conveying and sieving the working conditions are rough, large material quantities have to be processed and little room is available for the vibration drive.

Whether 1000, 1500 or 3000 vibrations/min is worked with, depends on the bulk material to be processed and the velocity of conveying to be achieved.Here applies the following rule:

High vibration speed at about 3000 vibrations/min is appropriate for fine-grained goods and low vibration frequency at about 1000 vibrations/min for coarse-grained goods.

Application Conveying

To ensure an efficient function of the chute (or the sieve), in addition, the following points have to be taken into account at the construction of a conveying chute (or a sieve).

  • The front and the back hanging should be equally far away from the center of gravity, but as far as possible from each other.
  • The relation between length and height of a conveying chute should be 5:1.
  • Another condition for the synchronization of the two external vibrators is that they are connected with each other absolutely vibration-rigid. The conveying chute also must be extremely stiff because of the dynamic load. In order to fulfil this requirement at an acceptable weight, free-running conveying chuts are maximal 6 m long.

Application Sieving

Vibrating screens are used to sieve out bulk materials, in order to e.g. to separate different material sizes or for draining of gravel or sand. The function of vibrating screens is similar to conveying chutes; the bottom, however, is a sieve. The sieve bottom is constructed in many forms and variations (round hole, slot, quadrangle) according to the material to be sieved. There are sieves with several, under each other arranged screen floors, dewatering screens, analysis screen, etc.

The difference to conveying technique is the attack angle of the external vibrators which again are attached in pairs and are counter rotating. The attack angle at sieving is steeper so that the conveying good particle hits the sieve as vertically as possible at the screen bottom; thus the conveying good particle goes better through the screen. Moreover, a better self-cleaning of the screen is given this way since particles being stuck are lifted easier at the next vibration. The attack angle at sieving should be 45°. The throwing range must correspond to the mesh width of the sieve screen.