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Guide to

External Vibration


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Circular vibration Linear vibration

According to vibrator type, vibration is

generated by:

- the rotation of an eccentric shaft (circu-

lar vibration),

- the reciprocating linear displacement of a

weight (linear vibration).

Note:the combination of two circular vibra-

tions of same speed, intensity and opposite

direction produces a linear vibration.

Power sources

There are electric and pneumatic vibrators.

Vibrator types

Electric vibrators: the shaft of an asyn-

chronous motor bears eccentric weights

at each end. Electric vibrators produce

a circular vibration.

Pneumatic vibrators producing circular

vibration: compressed air ow rotates

an eccentric weight in a circular cham-

ber. Main categories: turbo-vibrators

and ball-vibrators.

Basic knowledge

Vibrators in Industry

Atlas Copco external vibrators have wide and varied uses in most industries from

mining to food. Vibrators solve many material handling problems and save money

for industry through increased production and decreased labor costs. This brochure

shows some of the most common applications for vibrators and suggests proper

mounting locations for best results.

Contents

Basic knowledge ................... 2

Hopper discharging .............. 4

Form Vibration ...................... 6

Vibrating Tables ..................... 8

Screening ............................ 10

Feeding ................................ 12

Dust Collectors .................... 14


3/16

Power source selection

Selection depends upon site power supply,

safety, health regulation,working condi-

tions a.s.o.

Formulae for circularvibrations eccentric torque

Mo = Po x ro

Po = eccentric weight (kg)

ro = rotation radius = distance between

centre of gravity and rotation axis (cm)

Mo = eccentric torque (kg x cm)

Centrifugal force

n = frequency (r.p.m.)

Fc = centrifugal force (N)

Working moment

Mt = 2 x Mo

Mt = working moment (kg x cm)

Vibrator amplitude

Q = vibrating weight

vibrator weight + load weight (kg)

u = vibrator amplitude (mm)

Total vibration amplitude

s = 2 x u

s = total amplitude (mm)

Acceleration

a = acceleration (m/s2)

Changing operating data

R.p.m. and frequency of an electric vibra-

tor are determined by the electric motor

and inlet current specications.

Centrifugal force can generally be

adjusted by changing the eccentric weight

settings.

Performances of pneumatic vibrators

stated on data-sheets can continuously be

changed according to air pressure and ow.

Basic calculations

The experience gives average and practi-

cal value for the acceleration to be applied

to the load and calculation formulae for

evaluation of the requested centrifugal

force for the most important applications.

The formulae hereafter mentioned lead

to a rough evaluation of the requested

vibrating equipment according to the

installation and material data.

They are valid for rigid structures only.

Total amplitude

Centrifugal force

s = total amplitude (mm)

Fc = centrifugal force (N)

Q = vibrating weight (kg)

n = frequency (r. p.m.)

For the classical applications, practical

rules and calculation formulae have been

established.

They are summarized in the following

pages.

Important

The recommendations and practical

values hereafter mentioned have been

established following real applications.

All these indications lead to average

solutions suitable for most of the current

projects. They are not liable to engage

Atlas Copcos responsability.

Experience shows that a number of

building details may inuence the reac-

tions of the structure under vibrations to a

large extent. This is the reason why a thor-

ough examination or a preliminary test of

the structure is often recommended.

Mo 2 nFc = x100 60

2

Mo x 10u = Q

Fc

a = Q

182,315 x Fcs =

n2Q

Q nFc = s x 0,559 x x9,81 1,000

2

Inlet currentfrequency

(Hz)

Electricmotor nr. ofpole pairs

Speed(r.p.m.)

50 3 1.000

60 3 1.200

50 2 1.500

60 2 1.800

50 1 3.000

60 1 3.600

150 1 9.000

180 1 10.800

200 2 6.000

240 2 7.200

ro

n

u

S=

2xu

Guide to Vibration 3


4/16

Hopper discharging

4 Guide to Vibration

Recommended vibrators

Atlas Copco normal speed (3,000 r.p.m.)

electric vibrators and Atlas Copco ball or

roller pneumatic vibrators give best results.

Centrifugal force

The required centrifugal force for pro-

moting ow in bins and hoppers usually

ranges from one twentieth to one tenth of

the weight of material in the cone section.

For example, a vibrator producing 2,500

N of centrifugal force is suitable for a

hopper cone section containing 2,500 to

5,000 kg of material.

Location

One or several vibrators are required

according to the size of the hopper. Fix

the rst one to the side with the small-

est angle of inclination to the horizontal

line; level: 1/3 of total height of conical

part. Fit the vibrator horizontally on a

500-1,500 mm stiffener (4 channel iron).

Clearance between the channel iron ends

and hopper edges or hopper stiffeners

must be 200 mm or more. The vibrator

must be fastened with a safety wire.

When several vibrators are xed on the

same hopper, the minimum vertical dis-

tance between two of them is 100 mm.On hoppers with rigid wall, the

vibrator(s) must be tted on vibrating

surface(s), as shown on mounting sketch.

Important

Operate the vibrator only when emptying

the hopper, otherwise the material will be

packed intensively, causing considerable

problem with discharging.

Note: Air Blasters

This device is xed to the hopper wall and

discharges high speed compressed air right

into the material, turning it into a uid state,

and thus moving it.

The complete installation is made of

air inlet hoses, tanks which are xed to the

outer side of the hopper wall and discharge

pipes going through the wall.

Air blasters give the same results as

vibrators.

Centrifugal force:1/20 to 1/10 of weight of material in the cone section

of the hopper.

Recommended vibrators:normal speed (3,000 r.p.m.) electric vibrators.

Fitting a Atlas Copco pneumatic or hydraulic vibrator on a truck

improves discharging of materials (the vibrator is powered by

the pneumatic or hydraulic circuit of the truck).

A Atlas Copco pneumatic vibrator improves the emptying of a

wagon.

In handling bulk granular materials

through hoppers ans silos the material

often jams, bridges, rat-holes or sticks

causing interruptions in proper out-flow. These blockages generally cause

stoppages throughout the entire plant.

Substantial costs are incurred because

of loss of production and increased labor

required to clear the blockage. By means

of vibrators, such problems can be

solved easily and often quietly.


5/16

Fig. 2: Hopper and silo> 250 cu feet (> 7 m3). Position of the vibra-

tors.

Fig. 3: Hopper and silo of concrete or heavy sheet construction.

Position of the vibrating device.

Fig. 4: Hopper of wood construction. Position of the vibrator.

4 pcs hole shouldbe done in the wall

for vibration transmission

Flat springs

max.6(2,000

mm

)

min.1/3(100

mm)

Yoke

max. 6 (2,000 mm)


Fig.1: Hopper 10-250 cu feet (0,25-7 m3). Position of the vibrator.

4 channel iron U-100

Safety wire

2-5 (500-1,500 mm)

Motor vibratorBracket

Min. 2/3(200 mm)

1/3 L

4 channel iron

Safety wire

L

2/3

L

2-5(5

00-150

0mm)

min

.2/3

(200

mm)

1/3L

4 channel iron U-100

Safety Wire

2-5(50

0-1

,500

mm)

Bolt

Bracket


6/16


Form Vibration


For tables, trestles, beam forms and most

other horizontal type forms Atlas Copco

3,000/6,000 r.p.m. electric vibrators andpneumatic vibrators are recommended.

On vertical forms, high frequency pneu-

matic or electric vibrators are more suit-

able. Vertical pipe forms can be equipped

with Atlas Copco 6,000 r.p.m. or high

frequency electric or pneumatic vibrators.

Centrifugal force

Rule of thumb: force requirement is one

pound of centrifugal force for each pound

of concrete (based on 3 inch slump). For

drier concrete, more force is required. The

calculation formula for a rough evaluation

of the required centrifugal force is:

Fc = K (M + 0.2 B),

Fc = centrifugal force in N,

M = form weight in kg,

B = concrete weight in kg,

K ~ = 5 for vertical forms (beams, walls)

K ~ = 5 to 10 for horizontal forms,

K ~ = 15 for vertical pipes.

Required number of vibrators

1) Permanently xed vibrators:each

vibrating point is equipped with one vibrator.

2) Quick release type vibrators:the

number of vibrators is lower than the total

number of brackets (tunnel and long beam

forms).

3) Precast concrete factory:each form

is equipped with the required number of

brackets.

The required quantity of vibrators is:- the number of vibrators for the largest form,

or

- the number of vibrators for one casting.

Location

Horizontal forms : x the vibrators on the

stiffeners in a zig-zag formation.

Minimum distance between 2 vibrators:

l.5 m.

If the form has several sections, each of

them must get at least one vibrator.

If the form width is more than 2.5 m,x the vibrators on two rows - clearance

between row of vibrators and form edge

must be 14 of total width.

If the form width is less than 2.5 m, x

the vibrators in the middle.

On horizontal forms , the vibrators can

be xed on the long sides in order to facili-

tate mounting.

On large forms for single or double

Ts (height > 2m) x the vibrators on two

rows:

2/3 at the low level,

1/3 at the high level.

Vertical forms: x the vibrators on the

stiffeners in a zigzag formation.

Minimum distance between two vibra-

tors: l.5 m.

If the form height is more than 2.5 m,

x the vibrators on 2 rows, if it is more

than 4 m, on 3 rows ...

Vibration is widely used in the produc-

tion of precast concrete elements, in

order to obtain high strength, void free

filling and good surfaces. The form canbe placed on a vibrating source (vibrat-

ing table or trestle) or it can be equipped

with vibrators. Forms for pipes, beams,

single and double Ts, wall and floor

sections are generally equipped with

vibrators.

Centrifugal force:Fc = K (M + 0.2 B)Vertical forms: K ~ 5

Vertical pipe forms: K ~ 15

Horizontal forms: K ~ 5 to 10.

Recommended vibrators:electric 3,000/6,000 r.p.m. for horizontal form

- electric 6,000 r.p.m. or high frequency pneumatic vibrators for vertical

forms.


7/16


Fig. 5: Vertical form for pipes. Position of the vibra-

tors.

Fig. 6: Vertical form: Position of the vibrators.

Fig. 7: Horizontal form: Position of the vibrators.Fig. 8: Form for columns and beams. Position of the vibra-

tors.

3

1,0

00mm

5-81,5

00-2,5

00mm

5-8

1,5

00-2,5

00mm

2-3500 - 1,000 mm

5-81,500 - 2,500 mm

5-81,500 - 2,500 mm

5-81,500 - 2,500 mm

2-3500 - 1,000 mm

5-8

1,500-2,

500mm

3

1,0

00mm5

-8

1,5

00-2,5

00mm


8/16


Fig. 9: Vibrating trestle with circular vibra-

tion. Position of the vibrator.

Vibrating Tables and Trestles for Form Vibration


Atlas Copco normal speed electric vibra-

tors are most of the time used for this kind

of applications. However, Atlas Copcohigh and low speed electric vibrators as

well as pneumatic vibrators are suitable.

Centrifugal force

The formula hereafter gives a rough eval-

uation of the required centrifugal force.

- loose formFc = K (Mt + 0.2 M + 0.2 B)

- xed form

Fc = K (Mt + M + 0.2 B)

Fc = centrifugal force in N

Mt = weight of the vibrating part of the table

or trestle (including vibrators) in kg

M = weight of form in kg

B = weight of concrete in the form in kg

K = factor depending on concrete mix and

form rigidity (average values: from 20

to 40).

Location

In the case of circular vibration, the vibra-

tor is xed under the table plate or the

trestle right under its centre of gravity.

For linear vibrations, 2 identical elec-

tric vibrators must be xed parallel to the

vertical plan of symetry and at the same

distance from the centre of gravity of the

table or trestle. They must rotate towards

each other (applications: light and smallproducts casting).

Centrifugal force:

- Loose form Fc = K (Mt + 0.2 M + 0.2 B)

- Fixed form Fc = K (Mt + M + 0.2 B)

K ~ 20 to 40

Recommended vibrators:normal or high speed electric vibrators,

pneumatic vibrators.

Fig.10: Vibrating table with circular vibra-tion. Position of the vibrator.

Vibrating tables and trestles are widely

used in the production of precast con-

crete elements. The form is placed on

the vibrating table or trestle and filledwith concrete.

The vibrations compact the concrete

in a short time.

I-profile with transversal stiffenings

Rubber

support

Table sheet

Rubber support

Frame


9/16


Vibrating Tables: other applications

In addition to concrete precast industry

applications, vibrating tables are widely

used in a large number of activities for

compacting bulk materials in containersand drums. Vibration leads to reduced

handling, freight and spillage costs. It

helps increasing production through

high speed automated filling, weighing

and packaging operations.

In the casting industry, vibrating tables

are used for moulding and coring sand

compaction.

During vibration, bulk materials areturned to a uid state practically without

internal friction. The particles are moved,

and air escapes as they rearrange themselves

closer to each other. This usually occurs

within a few seconds and leads to compac-

tion ratios from 10 to 50%.

The grid-top vibrating table is widely used

in modern, automated, high capacity lling

lines; this table has vertical supports that raise

between roller conveyor rolls, thus lifting and

isolating the container during vibration cycle.

Tables can also be used for dischargingcontainers and drums as well as for shake

and fatigue testing of electronic and machine

assemblies and many products and instru-

ments.

Within a few seconds, a vibrating table

simulates the behaviour of goods on a

crosscountry trip by rail, truck or air,

thus enabling to check the accuracy of

circuitry or reliability of assembly.

Jolting of sheets of paper, veener

sheets, nesting and orienting of various

manufactured items are some other appli-

cations of vibrating tables.

Centrifugal force:

- Loose load Fc = K (Mt + 0,25 C)

- Fixed load Fc = K (Mt + C)

K ~ 20 to 100 according to application.

Recommended vibrators:Normal speed (3,000 r.p.m.), electric vibrators.

Fig.11: Vibrating table with circular vibra-

tion. Position of the vibrator.

Fig.12: Vibrating table with vertical linear

vibration. Alternative position of thevibrators.


According to their size and applications,

vibrating tables can be equipped with

one or two Atlas Copco pneumatic, lowor normal speed electric vibrators or one

pneumatic piston vibrator.

Centrifugal force

The calculation formula for a rough evalu-

ation of the required centrifugal force is:

- loose load

Fc = K (Mt + 0,25 C)

- xed load

Fc = K (Mt + C)

Fc = centrifugal force in N.

Mt = weight of the vibrating part of the

table (including vibrators) in kg.

C = weight of the load in kg.

K = factor depending on application:

moulding and coring sand compaction

K ~ 30, bulk materials compaction

K from 20 to 30, fatigue tests of

components K ~ 100.

Location

See page 8.

Table sheet

Table sheet

Rubber support

Rubbersupport

Frame Frame


10/16


Location

A vibrating screen consists of a frame, one

or more screen clothes, a vibration unit

and a spring mounting or suspension. The

vibration unit is made of 1 or 2 vibrators.

If the screen is equipped with one motor

vibrator, (circular vibration), the screen

must be declined 10o or more in order to

promote a good ow of material on the

screen cloth.

If the screen is equipped with 2 identi-

cal vibrators (linear vibration), it may be

horizontal. The vibrators must be positio-

ned 45 o in relation to the screen so that

the line of action of the vibration passes

through the centre of gravity of the screen(including the vibration unit).

According to the application, the 2

vibrators can be mounted either above,

under or on each side* of the screen. The

2 vibrators must rotate towards each other.

Note: Before xing the vibrator(s) on a

vibrating structure such as a screen, check

that the suspension system is correctly

installed and take the dynamic reactions

of the structure into consideration.

* In this case, distance between the vibra-

tors makes synchronisation more difcult.

Screening is another field of applica-

tion for vibrators. Vibrating screens are

mainly used in:

- sorting material by size into different

fractions (gravel and crushed aggre-

gates for instance);

- check screening (removing of core

lumps and alien materials from mould-

ing sand);

- dewatering (twig and bark dewatering

in the pulp and paper industry; dewater-

ing of vegetables).


Atlas Copco standard (3,000 r.p.m.) vibra-

tors usually give best results. Required

frequency is in inverse proportion with

screen cloth opening (the larger the ope-

ning, the lower the r.p.m.).

Note: Vibration amplitude

The screen cloth opening size xes the

amplitude of vibration: the larger the

opening, the greater the amplitude of the

screen.

With a cloth opening of 1 mm for

instance, the amplitude should be 0.5 mm;

it should be 2.5 mm for an opening of 30

mm and 6.5 mm for an opening of 100mm.

Centrifugal force

The centrifugal force and amplitude of the

vibrators depend on cloth opening size

and type of vibration. The rule of thumb

for an inclined screen with a circular

vibration is: the required centrifugal force

must be 3 to 4 times the total weight of

the screen

(including the vibrators). For all screening

installations, the manufacturers recom-

mendations are very useful.

Centrifugal force:3 to 4 times the total weight of thescreen

(including the vibrators).

Recommended vibrators:standard (3,000 r.p.m.).

Screening


11/16


Fig. 14: Vibrating screen with linear vibra-

tion. Alternative position of the vibrators.

Fig. 13: Vibrating screen with

circular vibration. Position of the

vibrator.

Spring suspension

Screen cloth10

Screen cloth

Anchor plateStiffenings

Spring suspensionor spring support

45


12/16


Feeding

Flow of bulk materials from hoppers

and silos is another handling problem in

industry.

Vibrating feeders promote a regularflow of material to conveyors, crushers,

mills and other processing equipments.

The shape of the hopper discharge

opening has a significant influence on

flow performance. The opening design

must allow the pressure of material to

be absorbed by the hopper. If not, a

column of material will remain on the

feeder, and more powerful vibrarors will

be necessary.


Atlas Copco low speed and normal speed

vibrators give the best results the higher

the feeder capacity, the lower the vibratorfrequency.

Electric vibrators (3,000 r.p.m.) are rec-

ommended when an accurate regulation of

the ow is required.

Centrifugal force

The required centrifugal force depends upon

the feeder size. The average value is 4 to 7

times the total weight of the installation.

Location

The main parts of a feeder are a trough,

spring suspension elements and one or

two vibrators.

If the feeder is equipped with one

motor vibrator, it must be declined 15

at least. The vibrator is xed under the

trough so that the line of action of the

vibration passes through the centre of

gravity of the feeder.

When equipped with 2 identical motor

vibrators, feeders are designed to work

horizontally.

Vibrating feeders equipped with Atlas

Copco normal speed electric vibrator.

When installed in series, they allow long

distance material transport. Furthermore a

treatment can be applied during transpor-

tation (heating, cooling, dust cleaning ... ).The two Atlas Copco motor vibrators

must be xed 25 to the horizontal, and

the line of action of the vibration must

pass through the centre of gravity of the

feeder.

Note:Material introduction on feeders.

The material ow intake must be as

constant as possible in order to obtain a

good feeder efciency.

Any material build-up from hopper on

the intake side of the feeder will reducetransport capacity.

In a number of applications, vibration

does not move materials or products; it

keeps ow regular and prevents installa-

tion stoppage by clogging or blockage.

Small Atlas Copco pneumatic vibrators

are often used for this purpose: they work

intermittently, and their control is either

manual or automatic by sequence.

The drawings hereafter show some

usual applications.

Centrifugal force:Fc = K (Mc + 0.25 C).

K ~ 40 to 70 according to application.

Recommended vibrators: Normal speed (3,000 r.p.m.) vibrators.


13/16


One Atlas Copco ball vibrator impro-

ves efficiency of this tin transportation

system.

Working intermittently, a Atlas Copco

pneumatic vibrator promotes a regular

material flow in this pipe.

One Atlas Copco ball vibrator avoids bottle

blockage on this conveyor.

Fig.l5: Vibrating chute. Position of the

vibrator.

Fig.16: Conveyor with linear vibration. Alternative position of the vibra-

tors.

15Spring suspension

Anchor plate Channel iron

Spring suspensionor rubber support

Stiffening

Anchor plate


14/16


Dust Collectors

Vibration is required for 2 kinds of dust

collectors: the fabric lter-bag type and the

electrostatic precipitator. In the rst type,

all the dust is collected by the lter bagswhich must be cleaned at regular intervals.

For this purpose, the vibraror shakes the

bags intermittently and the dust falls from

the bags into hoppers positioned below.

Furthermore, vibrarors are often used to

improve dust discharge and removal from

collecting hoppers. In electrostatic precipi-

tarors, the vibrarors are used to shake both

wire and plate frame, thus moving the dust

particles they hold. The dust falls into hop-

pers. In this case too, vibrators are often

used to help dust removal from collectinghoppers during cleaning cycles.

Centrifugal force: 3 to 4 times the vibrating weight.

Recommended vibrators:normal speed (3,000 r.p.m.) elec-

tric vibrators.

Fig.17: Dust separator with filter

bags.

Fig.18: Dust separator with filter sheets.


Atlas Copco normal speed electric vibrators

(3 ,000 r.p.m .) are recommended for this

application.

Centrifugal force

The required centrifugal force is between 3

and 4 times the vibrating weight (i .e. lter

elements + frame).

Location

A dust collector is made of an air-proof

box including a hopper at its lower side

and in which the collecting elements

are suspended. All the lter elements

are mounted on a common frame and

stretched by springs. The vibrator is xed

on a channel iron which is mounted on the

frame upper part.

Dust collectors help lowering air pol-

lution level and improving working

conditions.

4 channel iron should be positionedon the angle iron frame

Note:For effectively clearing,the filter bags should be stretched

Spring suspension

Angle iron

Motor vibrator


15/16

Atlas Copco

Vibration

Electric Vibrators Pneumatic Vibrators

Normal speed, ER type High speed, ER 7is type Turbo, EP type Ball, EB type

Mould vibration

Concrete

Sand

Materials

compaction

Discharging

Hoppers and silos

Dessanding

Cleaning

Filters

Transportation

Feeders and Con-

veyors

Screening

Screens

Vibrators have many applications which fall outside the categories previously

mentioned. This booklet can be used as a guide for quite a number of such

cases.

For suspended or spring mounted structures, choose the most similar listed

application: tables, trestles, screens or feeders . In the same way, recom-

mended Atlas Copco vibrators for bins, forms, hoppers are suitable for fixed

structutes such as pipes, chutes ...



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www.atlascopco.com

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