RECOMMENDATIONS FOR VIBRATOR SELECTION

TYPES OF VIBRATION
You can obtain three types of vibration:
CIRCULAR (fig. A): obtained with 1 electric vibrator positioned near the mass center of the equipment
ELLIPTICAL (fig. B): obtained with 1 electric vibrator positioned distant from the mass center of the equipment
LINEAR (fig. C): obtained with 2 electric vibrators (counter-rotating) positioned so that the line of force goes through the mass center of the equipment

The functioning of a vibratory equipment is the result of a specific know-how and experience, it is recommended that only manufacturers of equipments specialized in that field make all necessary evaluations and relevant calculations. Anyway, for a preliminary evaluation of the vibrator model suitable for an application, we report here below some formulas to be considered only as not-binding indications.
GENERAL FORMULA AND LEGENDA Quida alla scelta del vibratore indutriale
S (stroke) = e * 2
[mm]
e (eccentricity) = SMt / Wt
[mm]
a (acceleration) = CFt / Wt
[G]

Wt (total weight of equipment) =
We + Wvt
[kg]
We (weight of isolated equipment)
[kg]
Wvt (total weight of vibrators) =
Wv * nr. vibrators
[kg]
Wv (weight of vibrator)
[kg]
SMt (total static moment) =
SMv * nr. vibrators
[kg*mm]
SMv (static moment of vibrator)
[kg*mm]
CFt (total centrifugal force) =
CFv * nr. vibrators
[kg]
CFv (centrifugal force of vibrator)
[kg]
α (line of force angle from horizontal)
[°]

EXAMPLE OF VIBRATOR SELECTION
Given data on equipment and process
Type of process / vibration:
primary feeder / linear vibration
Weight of equipment (We):
1.500 kg
Feeding Frequency:
50 Hz
Speed / Poles:
1000 rpm / 6 Poles
Requested stroke of vibration (S):
8,0 mm


Calculations
Eccentricity (e)
= S / 2 -> 8,0 / 2
= 4,0 mm
Weight of vibrators estimated (Wvt)
= 20-25% of equipment weight -> 25% of 1.500 kg
= 375 kg
Total equipment weight (Wt)
= We + Wvt (estimated) -> 1.500 + 375
= 1.875 kg
Total Static Moment (SMt)
= Wt * e -> 1.875 * 4,0
= 7.500 kg*mm
Static Moment of vibrator (SMv)
= SMt / 2 -> 7.500 / 2
= 3.750 kg*mm


Selection and checking
When selecting the vibrator model, it is advisable to use, for all further calculations, the 80% of the value of Static Moment (SMv), therefore the 80% of the relevant Centrifugal Force (CFv), in order to have an operative safety margin of 20%.
In the Catalogue section “6 poles - 50 Hz - 1000 rpm”, we must identify a model that, with 80% of setting, will grant a value of Static Moment (SMv) the closest possible to the value required:

SPV 41.5 C
Static Moment (SMv)
= 4.300 kg*mm (100%) -> (80%)
= 3.440 kg*mm
Centrifugal Force (CFv)
= 4.800 kg (100%) -> (80%)
= 3.840 kg
Weight (Wv)
 
= 200 kg
Eccentricity calculation (e)
= SMt (80%) / Wt -> (3.440 * 2) / (1.500 + (200 * 2))
= 3,6 mm
Acceleration calculation (a)
= CFt (80%) / Wt -> (3.840 * 2) / (1.500 + (200 * 2))
= 4,0 G (it is advisable not to exceed 5,0 G value)

To obtain the requested eccentricity (e= 4,0 mm) we should set the vibrator at 90%. To keep the recommended safety operative margin of 20%, we have to consider the next model:

SPV 50.0 C
Static Moment (SMv)
= 5.100 kg*mm (100%) -> (80%)
= 4.080 kg*mm
Centrifugal Force (CFv)
= 5.700 kg (100%) -> (80%)
= 4.560 kg
Weight (Wv)
 
= 242 kg
Eccentricity calculation (e)
= SMt (80%) / Wt -> (4.080 * 2) / (1.500 + (242 * 2))
= 4,1 mm
Acceleration calculation (a)
= CFt (80%) / Wt -> (4.560 * 2) / (1.500 + (242 * 2))
= 4,6 G (it is advisable not to exceed 5,0 G value)

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THE PRODUCT