Useful Information

Acceleration Calculation:

How to calculate acceleration (G’s) of a vibrating screen/feeder
THROW – peak to peak in mm RPM – speed of vibration of machine in RPM

Screen Motion – Background:

For a vibrating screen to perform its’ operation “well” it needs to produce a motion that, when laden with feed material, is consistent down the length of the screen, is appropriate for the specific application and also the angle and nature of the screening surfaces.

In order to maximise the service life and reliability of the machine, the motion must be consistent across the screen (left to right). Significant variations in the throw of a screen, from one side to the other, and excessive transverse (sideways) vibration indicates flexing of major structural components (therefore higher internal stresses) resulting in premature failure.

Factors that govern the amplitude and nature of a screen’s motion are:

  • The magnitude and direction of the excitation forces and where they are applied relative to the centre of mass of the machine.
  • The mass of the screen and its’ components.
  • The effective laden mass of feed material.
  • The dynamic responses from within the screen itself and also the springs that support it and isolate its’ vibration from the supporting structure.

A machine that screens “well” and runs reliably for many years is one that:

  • Is well designed with its’ vibrating mechanism positioned so that a consistent motion is achieved, along with the decks, when the screen is laden with material.
  • Produces a motion that is appropriate for the feed material, deck angle, and type of media.
  • Has a well-balanced and aligned vibrating mechanism.
  • Is made up of components that a are consistent in mass from one side to the other.
  • Does not allow the material to build upon any part of the screen.
  • Is fed centrally with an unsegregated feed material.
  • Has no natural frequencies close to its’ operating speed.
  • Has support springs that have equal static compression between the left and right sides of the screen.

Screen Health and Motion – Guide Chart:

The following chart is a guide to help determine if the motion of a vibrating screen should be deemed acceptable, or not. It is based on experience with vibrating screens. It relates to screen structural health and not to screening operation or efficiency. Wherever possible and practicable, all effort should be made to have a screen running within the “good” range. This chart cannot be used to predict whether a screen will fail, or not. It is simply a practical guide.

ToThink Engineering

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