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TRANSCRIPT
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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
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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
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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.
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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)
Guide to Vibration 5
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
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6 Guide to Vibration
Form Vibration
Recommended vibrators
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.
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Guide to Vibration 7
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
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8 Guide to Vibration
Fig. 9: Vibrating trestle with circular vibra-
tion. Position of the vibrator.
Vibrating Tables and Trestles for Form Vibration
Recommended vibrators
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
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Guide to Vibration 9
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.
Recommended vibrators
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
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10 Guide to Vibration
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).
Recommended vibrators
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
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Guide to Vibration 11
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
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12 Guide to Vibration
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.
Recommended vibrators
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.
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Guide to Vibration 13
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
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14 Guide to Vibration
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.
Recommended vibrators
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
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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 ...
Guide to Vibration 15
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