Service Tip - Checking the amplitude of a vibrating screen

Among the conditions to be checked periodically in screens, the shape of motion is one of the most important. In the chart below, one can see and verify the shape of the vibratory motion: circular (A), elliptical (B) or even linear (C).

It is also possible to assess the amplitude of motion, as provided in the illustration below:

Let’s examine a few concepts related to amplitude:

• The amplitude of vibration does not depend on the rotation of the vibrating mechanisms.
• Amplitude combined with rotation imparts a certain amount of acceleration to the equipment and that acceleration is responsible for the conveyance of the material.
• The larger the material to be conveyed, the greater the vibration amplitude of the equipment should be.

There is an ideal relation between operating rotation, amplitude and the degree of inclination of the equipment depending on the aperture of the mesh installed on the screens. The nominal rotation is established observing the ideal operating conditions and, further, to ensure that the equipment is operated safely below the vibrating structure’s critical frequency.

Warning: Never alter the rotation of vibrating equipment before checking with the Metso Outotec equipment application area.

The amplitude of vibration can be altered by changing the position of the movable counterweight. Such adjustment is performed based on the application. The screening of coarse material demands a higher amplitude than the amplitude required for the classification of fines.

The following table provides the recommended values for total displacement (twice the amplitude):

Below you will find the table for adjustment of the vibratory mechanism of the V-100 Series:

For other models of vibrating equipment (such as feeders, chutes, etc.), please consult their respective manuals.

The higher the operating amplitude of vibrating equipment, the shorter the service life of the equipment’s bearings. Bearing service life will be satisfactory even if all the available eccentric mass that was originally provided with the equipment is used.

Warning: Never utilize eccentric masses that are greater than those provided as original equipment. This will lead to a considerable drop in the service life of the bearings, as well as a possible unbalancing of the vibrating equipment.

In order to precisely measure and analyze the dynamic performance of vibratory screens, we developed ScreenCheck®, a hand-held electronic testing device featuring wireless electronic sensors and automated software.