It is possible to obtain two types of vibrations:

ROTATIONAL: Using only one vibrator which generates a rotating centrifugal force around its own longitudinal axis transmitting it to the connected structure and creating an elliptical movement (fig.1).

UNIDIRECTIONAL: Using two vibrators with equal features, rigidly fixed on the same plane and rotating in opposite direction. In this case the centrifugal forces created by the counter-rotating eccentric weights generate an unidirectional alternating vibration (fig.2).

Revolution "n" (R.P.M.) and the static moment "M" (kg.mm.) are the most important characteristics of the vibrator.

To select the revolution it is important to consider the type of the application and the type of the material.

3000 R.P.M. vibrators are chosen when high frequency and low amplitude are required, generally to avoid loose materials clogging in silos, hoppers, ecc.
1500, 1000 and 750 R.P.M. vibrators are mostly used in conveying, screening and similar processes.

The efficiency of a vibrating machine is measured by the acceleration that it is able to transmit on material according to the following formula:

A=acceleration
a=amplitude of vibration peak-to-peak
n=revolution per minute (R.P.M.)
g=gravity acceleration=9,81m/s²

The acceleration of a vibrating machine should not exceed 10xg. For normal applications, the vibrator types should be selected so that the amplitudes are as follows:

0,5-2 mm. for machines which are equipped with vibrators at 3000 R.P.M.
4-6 mm. for machines which are equipped with vibrators at 1500 R.P.M.
6-12 mm. for machines which are equipped with vibrators at 1000 R.P.M.
10-16 mm. for machines which are equipped with vibrators at 750 R.P.M.

The vibration amplitude can be calculated with the following formula:

M = static moment of vibrator in kg.mm. (according to the catalogue)

P = weight of the machine (vibrators included) (kg)

VIBRATOR ADJUSTMENT

There are two parameters available to modify the efficiency of a vibrating machine:

• amplitude

• revolution

The amplitude can be altered by adjusting the weights only after having stopped the motor.

Revolutions can be regulated by inserting a variable frequency drive.

These regulations can be made when the vibrator is operating, directly by means of the drive or by a remote control. It is also possible to limit the oscillations that occur when the motor is switched off by using the braking characteristics of the frequency drive.

For selecting and setting the variable frequency drive it is necessary to consider:

a) all vibrators installed on the same machine must start together and be fed by the same drive.

b) it is important not to exceed the nominal speed of the vibrator, and, to avoid resonance problems, not to operate with less than 50% of this speed.

c) to assure good starting of the motor, we advise to use a frequency drive with a capacity which is about one and a half time as much as the total capacity of all vibrators installed on the structure.

For further informations refer to our Customer's Care Service.