pallA VIBRATING MILL

MBE Coal & Minerals Technology GmbH

MBE Coal&MineralsTechnology GmbH

Gottfried-Hagen-Str. 20, 51105 Cologne/Germany
Tel +49 221 99892 700
info@mbe-cmt.de
www.mbe-cmt.de

2. Print run 1500

Concept and Design Affairen-Gestaltung.de
Paper EuroBulk
Printed by Kettler Verlag, Bnen
Printed in Germany 2011

PALLA
VIBRATING MILL BROCHURE

The PALLA Vibrating Mill is used in a wide range of

applications for process engineering duties. Due to its
easy operation, versatility and operation efficiency
the PALLA Vibrating Mill gains in importance in the
mineral processing industry.
This PALLA brochure focusses on the technology and the
principle of ultra-fine grinding. In addition, it describes
a variety of operations and the benefits of these different
operating modes regarding product size and efficiency.
You will also learn more about the construction and
design of the PALLA particularly on special features
and development.

THE ESSENTIALS ENDURE. With its more than 150-year

history, while permanently being revised and improved,
the vibrating mill technology perfectly matches the essentials
of our companys principles, which is, first of all, continuity
with the courage to face change.

05 VIBRATING MILL TECHNOLOGy

07 GRINDING PRINCIPLE
09 DETAILS OF DESIGN
13 Research and development Centre
15 ScopeS of Services

03

PALLA
VIbrating mill technologY

The idea of employing a swinging motion as

a grinding principle was developed in the past
century. Since then the demands to product
grain size in the mineral processing industry
have been constantly increasing, therefore the
vibrating mill has been subject to a continuous
improvement.
The general purpose of size reduction is to
produce a well-defined grain size in order to
achieve an enlargement of the particle surface
or to decompose adhered materials. Furthermore ultra-fine grinding is applied for surface
activation within the mechanochemistry.
When increasing the particle surface, a
modification of the original mechanical and
chemical character may occur as a result
of mechanochemical reactions or activations.

Vibrating mills have hitherto proved their worth as individual machines.

Vibration grinding represents an economic and reliable solution since
the required product grain sizes can be achieved in a simple continuous
grinding process without air classifying.
For over 160 different materials, from soft to very hard, the vibrating mill
has been successfully established for grinding, homogenizing and activating.
A high filling degree of the grinding cylinders and a low air throughput
appear to be beneficial for materials like metals, coal, coke and other organic
materials, which tend to increase the risk of dust explosion.

CONCEPTION.The wide range of application can be described by the

following mill characteristics and operating conditions:
dry or wet grinding
different options for grinding cylinder connection
continuous or discontinuous grinding
indirect cooling or heating
dusttight, use of inert and protective gas, grinding compartment
with overpressure and negative pressure, special designs
grinding at cryogenic temperatures (PALLA VM-KT or PALLA UT)
different grinding media (rods, balls, cylpebs)
different materials for grinding media
(wear-resistant special steel or ceramic material)
filling degree of grinding cylinders
rotating frequency
acceleration

05

Dominant forces:
impact

Swinging body
supported on steel springs

PALLA mounted on
anti-vibrating foundation

Insignificant forces:
pressure and shear

Operative range of grinding media

PALLA
GRINDING PRINCIPLE

0,005
0,001

0,05
0,01

0,5
0,1

10

coarsest particle in product (mm)

coarsest particle in feed (mm)

20

30

Usually rotation impulses of 1.000 min- are transferred by the effect of

unbalanced weights from the surface of the grinding cylinders to the grinding
media which performs an almost ideal circular movement. Depending on
the frequency and the unbalanced mass, an acceleration of several g can
be generated (g=acceleration of gravity).The grinding effect is caused by
milling the feed material in between the elements of the grinding media and
between the elements of the grinding media and the cylinder walls. Size
reduction in vibrating mills is primarily caused by the impact energy of the
grinding media rather than by friction or by acceleration of the feed
material.The grinding cylinders are filled up to 65% with grinding media.
The diagram represents the general trends in media selection. Furthermore
the specific material properties like hardness, density, grain shape, surface
properties etc. have to be taken into account.
Three types of grinding media can be used in vibrating mills which, due
to their geometry, cause the different impulse transitions:
Rods: linear impact energy
Balls: punctual impact energy
Cylpebs: linear and laminar impact and friction energy

Consequently for achieving an optimal energy transmission the correct choice

of grinding media is essential.The feed is constantly charged to the grinding
cylinders and flows into the gaps of the grinding media via vibration where size
reduction and transportation occurs simultaneously.The spiral transportation
of material through the horizontal grinding cylinders is based on displacement
of material and is supported by the vibrating motion.The repose angle at the
outlet which controls the throughput depends on type and size of grinding
Grinding cylinder with rods media, feed size, material properties and circular motion.The degree of
size reduction mainly depends on retention time and besides others on the
throughput.

07

The processing of materials of different structure and chemical composition

requires a wide and versatile milling conception which can be realised with
vibrating mills in the following basic sizes PALLA VM, PALLA 20U, PALLA 35U,
PALLA 50U, PALLA 65U. The throughput depends not only on the machine
size but also on various other parameters like frequency, amplitude of vibration, arrangement of grinding cylinders and grinding media. With installed
drive capacities of up to 200 kW for wet grinding processes, the PALLA is one
of the most powerful and versatile vibrating mills available on the market.

Type Diameter Length

Throughput


(mm)
(mm)
(kg/h)
VM
200
300/600
0,1150
20U
200
1.249
20500
35U
350
2.306
503.000
50U
500
3.400
20010.000
65U
650
4.525
40020.000

Power
dry wet
(kW) (kW)
1,9
5,5
22
75
90
160 200

Grinding systems.The grinding cylinders

are manufactured of high-grade steel.The
tube lengths of all models ensure a superfine
grinding even without a separator. Inlet and
outlet caps have been flanged to the tube ends
for admitting and discharging the material.
A grit plate fitted between the cylinder and the
outlet cap retains grinding media (e.g. cylpebs
or balls) but allows the material to pass through.
Adjustable retaining cones in the outlet caps
permit optimum utilisation of the grinding compartment.
Sockets mounted to the cylinder top permit
quick inspections of the grinding compartment
and refilling with cylpebs and balls.
Flexible and airtight components couple the mill
to upstream- and downstream-mounted proportioning and conveying equipment so as to
minimize dust emissions. For this reason,
connection to a dust collector is normally not
necessary. All flange connections are sealed by
temperature-resistant O-rings.The cylinders
are protected by highly wear-resistant and
easily replaceable liners. For iron-free grinding
these liners are made of ceramic. Since the
liners are subject to low wear, they achieve long
service spans.

Grinding cylinder with grit plate

and retaining cone

Liner with fastening device

PALLA
DETAILS OF DESIGN

Fastening of grinding cylinders.The cylinders

of the PALLA Vibrating Mill are fastened to the webs by the
way of clamps and anti-fatigue screws.This arrangement not
only ensures secure fastening of the cylinders but at the same
time facilitates their easy replacement. Apart from that, the
risk of crack is eliminated, which may be implied in welded
joints of cylinders and webs.This avoids costly repairs and
downtimes.
Generating vibration.The drive is carried in the
centre of the robust web.The major drive components are two
cylindrical roller bearings, the drive shaft and two pairs of
unbalanced weights.The latter are easily accessible and can
be quickly adjusted relative to each other in very small steps.
Consequently there is no difficulty in accurately matching the
diameter of the vibrating circle to the feed material, thereby
achieving optimum size reduction.The roller bearings of high
load-carrying capacity have been fastened in the webs in such
a manner that the complete unbalanced drive can be easily
removed for inspection or repairs.The squirrel cage motor
which drives the mill has been mounted on a bracket at the
front of the machine. It is connected directly to the shaft of the
front unbalanced drive via a cardan shaft.The drive is
of such design that no axial forces act on the mill bearings.
The motor can be set up at either end of the machine.

Electric connection. Electric connection and circuit

The replaceable bearings seats for

PALLA 50U/PALLA 65U. Along with advantages in the
design of our PALLA U Vibrating Mills, the cylindrical
bearing assembly of the PALLA 50U and PALLA 65U has
been significantly improved.
The roller bearing assemblies are carried in replaceable
bearing bushes screwed to the webs of the grinding mill and
transmitting forces exclusively by way of static friction.This
new feature allows simple, fast and cost-effective elimination
of damage at the bearing seat, caused e.g. by faulty operation,
simply by replacing bushes. Consequently the web does not
require replacement and the mill therefore does not have to
be dismantled.

Insulation. Vibration isolation by means of the elastic

elements means that the relatively small dynamic forces
are transmitted from the vibrating machine to the supports.
Therefore, special foundations are hardly ever required.
Even strict isolating requirements can be met also in case
of adverse site conditions by using a foundation with precisely
calculated damping mass.
When installing vibrating mills in open buildings or in close
vicinity to working areas, it is recommended to have them
enclosed for sound abating.

connection of the motor depend on the local regulations

and local capability of the supply network.The motor should
be laid out so that the starting torque equals at least
2,2 times the rated torque.The direction of rotation of the
motor is optional. Alternating operation will considerably
extend the service life of the cylindrical liners. Mill operation
can be monitored with aid of an ammeter which indicates
the power consumption of the motor.

B earing unit

09

Grinding cylinder connection.The following options for the

connection of the grinding cylinders for grinding process are possible.
Series connection: With this type of arrangement, the feed passes both
grinding cylinders successively, with results in maximum grinding path
lengths and longest retention times of 12minutes.
This connection is applicable for fairly hard or coarse feed, for very fine end
products, for materials which are characterized by poor blending properties,
or for long grinding, dissolving and reaction processes.
Parallel connection: With this arrangement, either cylinder yields a finished
product and shorter retention times of 3 12minutes and higher throughput
rates can be achieved. Identical or different materials can be ground, blended
or chemically treated in the two cylinders at the same time.
This arrangement is suitable for materials that are easy to grind, for closed
circuit grinding, for simple blending operations and dissolving processes as
well as for chemical reactions of short duration.
Centre feeding: In this configuration the material flows in either direction
towards the outlet caps. Grinding path and retention time are very short
and the throughput is correspondingly high. Size reduction is less than
under series or parallel connection.This arrangement is suitable for soft
materials requiring minor grinding only or any other substance to reach
a product as coarse as possible, for quick chemical reactions or for dissolving processes.

Special designs. Due to the application of PALLA in

so many different branches of industries, the vibrating mill
sometimes requires a special design.
The PALLA can be constructed and installed in a vertical
or horizontal design, whereas the vertical is more common
because of its smaller footprint.
The CRYOPALLA is a time-proven machine for grinding of
metals or other materials which are difficult to grind at
normal temperatures. In a CRYOPALLA the feed material is
brittled by cryogenic agents down to 185C and then reduced
in size. Due to its special design this grinding mill enables
cost-effective grinding at low temperatures.
The PALLA EX generates, a combination of elliptical, circular
and linear vibration.This ensures an efficient circulation of
the grinding media and grinding material with a positive
degree of aeration and generates in addition to the impact
forces, also friction.There is less accretion of very soft
products at the grinding media and the grinding walls.
Furthermore double-walled cylinders are used which enable
cooling or heating with water or brine in order to maintain a
given material temperature.
Our focus is the flexible and optimal realisation of our client
wishes regardless of the complexity.

Horizontal PALLA
CRYOPALLA
Grinding cylinder water cooled design

11

Our company-owned R&D centre is an important body between theory and

practice. Since for most materials the grindability is unknown, milling tests
are normally required prior to the design of a vibrating mill. Laboratory scale
test works are carried out in order to verify the different machine parameters
of dimensioning the PALLA and all other crushing, grinding and sorting
equipment.Estimating the throughput for each material requires milling
tests in which different parameters like frequency, amplitude of vibration,
arrangement of grinding cylinders and grinding media are determined.
The optimal mill design depends on the application, material properties,
feed and product grain size, size distribution as well as grain shape and
surface.
The test works are executed in a laboratory scale, vibrating mill for dry
and wet grinding.The results can be upscaled to any vibrating mill size.
Small sample quantities of different feed materials allow rapid and economic
pulverisation and extrapolation.
Feed and product grain size analysis can be offered whether with air-jet sieve,
wet screening or laser granulometer.

Research and development Centre

PALLA VM.The results obtained can be transferred without restriction

to industrial scale systems.Three different types are offered, i.e.:
VM-S. Enabling individual tests for rapid process optimisation at low
expenditure and with small material quantities (approx. 12kg).
VM-K. Designed for short- and long-term tests
(up to 100 kg/h depending on feed properties) for process optimisation.
VM-KT. Permitting tests as detailed as for type VM-K above but
for temperatures down to 185C.

13

980 (20U)
1575 (35U)
2245 (50U)

670 (20U)
976 (35U)
1596 (50U)

1616 (20U)
2525 (35U)
3622 (50U)

560 (20U)
800 (35U)
1300 (50U)

2735 (65U)

4940 (65U)

1790 (65U)

1500 (65U)

ScopeS of Services

After-sales service. Utilising our

from the first step up to the Commissioning.To realise

considerable logistical, engineering and site

service expertise, MBE Coal & Minerals
Technology GmbH aim to provide an unpar
alleled level of ongoing services.These
services will maximise the operators return
on their investment throughout the lifetime
of the equipment.
We believe that strong partnerships can only
evolve with personal contact. From the
outset we have assigned an Account Manager
who will learn about your business and
understand its unique demands. Utilising
that knowledge and by focussing on what is
important to each individual customer, we
can develop an operational plan that will
ensure we deliver on our promises on time
and within budget.

your projects you can receive the entire scope of services from one
source, i.e. from us:
Project consulting by globally experienced mining, process, mechanical
engineers and mineralogists.
Test work in our own R&D centre and laboratories.
Feasibility studies in joint effort of clients personnel familiar with the project
targets and our competent employees, even up to project financing.
Plant design with basic and detail engineering including project
management.
Supply of equipment, systems and plants.
Training of end users personnel for management functions same as for
operators and maintenance employees, in our offices, in our R&D centre, in
our reference plants all over the world, and finally on end users site.
Installation/supervision of installation of our equipment and systems by
or own globally experienced service specialists.
Commissioning of equipment, systems and plants.
After-Sales services including not only supply of parts and respective
services but also consultancy in respect of operation and maintenance
of our equipment.

The four key services we offer to maintain

and improve the operation of your equipment:
competitively priced OEM spare parts with
lead times to meet the customers operating requirements
w e carry out planned service visits at
mutually agreed intervals with an optional
emergency call-out service and operator
training
upgrade packages for your equipment to
improve performance, based on our most
recent product developments
equipment refurbishment
Continue to utilise our people and expertise
to maximise the efficiency of your operations.
We will not let you down.

15

MBE Coal & Minerals Technology GmbH

Gottfried-Hagen-Str.20, 51105 Cologne/Germany
Tel +49 221 99892700, Fax +49 221 99892709
info@mbe-cmt.de
MBE Minerals SA Pty. Limited
36 Wankel Street Jet Park Bok sburg 1459
PO Box 8460 Elandsfontein 1406/South Africa
Tel +27 11 3974660, Fax +27 11 3974411
southafrica@mbe-cmt.com
McNally Humboldt Wedag Minerals India Pvt.Ltd.
Ecospace Campus -2B, 3rd Floor, 11F/12 (Old Plot No.AA II/Blk-3)
New Town Rajarhat, North 24 Parganas Kolkata 700156/India
Tel +91 33 66281111/30141111, Fax +91 33 30142234/66282234
india@mbe-cmt.com
MBE Minerals Processing Technology Beijing Co.Ltd.
25-01, CITIC building, 19 Jianguomenwai Street, Chaoyang district,
100004 Beijing/P.R. China
Tel +86 10 85262536, Fax +86 10 65008588
china@mbe-cmt.com
MBE Coal & Minerals Technology GmbH
Representative office in Moscow
Myasnitskaya str, bld.1 24/7, Office 108, 101000 Moscow/Russia
Tel +7 4956251844 , Fax +7 4959894125
info-ru@mbe-cmt.com
MBE Processamento Mineral do Brasil Ltda.
Rua Rio Grande do Norte No.1560 salas 701 e 702
CEP.30.130.131 Belo Horizonte, MG/Brasil
Tel +55 31 37855224, Fax +55 31 37860857
brasil@mbe-cmt.com
PT MBE Coal and Minerals Technology Indonesia
Plaza Mutiara 17th Floor Suite 1702
Jl. Lingkar Mega Kuningan Kav East 1.2/1 and 2
Jakarta Selatan 12950/Indonesia
Tel +62 21 57852301/57853154/57900196, Fax +62 21 57900265
indonesia@mbe-cmt.com
MBE Cologne Engineering GmbH
Dillenburger Str.63, 51105 Cologne/Germany
Tel +49 221 99892600, Fax +49 221 99892619
info@mbe-ce.com
McNally Bharat Engineering Company Limited/Head Office
Ecospace Campus -2B, 11F/12 (Old Plot No.AA II/Blk-3)
New Town Rajarhat, North 24 Parganas Kolkata 700156/India
Tel +91 33 66281111/30141111, Fax +91 33 66282277/30142277
mbe.corp@mbecl.co.in