function and task of the bead millfile.yizimg.com/362064/2013010415570082.pdfin principle, two...

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In many technical processes it is necessary to divide solidmaterial into fine particles anddistribute them evenly within a liquid carrier. This process isgenerally known as ”dispersion”.During dispersion, the adhesive forces that act between the extremely fine solidmatter powder particles mustbe overcome. When the requirements on fineness arehigh or the solid matter is difficult to disperse, a dispersionwith the dissolver is often insufficient.

Due to their ability to process awide variety of solid matters thatare difficult to disperse, highspeed bead mills have gainedparticular acceptance.

Function and task ofthe bead millIn the dispersion process, threepartial steps run in parallel:

1. The wetting of the surface ofthe solid matter to be processed,by liquid components of the millbase.

2. The mechanical division ofagglomerates into smaller agglomerates and primary particles.

3. The stabilisation of primaryparticles, agglomerates andaggregates against renewedattraction (= flocculation).

Introduction to Dispersion Technologywith the Bead MillDISPERMAT® SL

While the stabilisation againstflocculation is primarily a property of a colloid-chemicalsystem, which depends on theinteraction of the liquid components (in varnishes forinstance: binders, solvents andadditives) with the solid matterparts (e.g. pigments and fillers)or on that of the solid particleswith each other, the dispersionmachinery used plays a vitalpart in the mechanical divisionand more important aids thewetting process.

The actual dispersion system ina bead mill consists of a millingchamber and an agitator; themilling chamber is filled with thegrinding beads (material e.g.glass, zircon oxide, steel) andthe product to be dispersed. Inthe milling vessel, the grindingmedium is kept moving by theagitator, which itself is driven bya motor. The dispersion processtakes place between the grinding beads sliding on eachother and between the rotorand/or the vessel sides and the grinding beads.

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The Step of Mechanical Division in DispersionJust like the dispersion, themechanical process can be divided into the three steps

● wetting

● mechanical division

● flocculation stabilisation

The step of mechanical divisioncan itself also be separated. To enable the agglomerates tobe dispersed, they must

● get into a dispersing situation, e.g. into the shearing zone between two grinding beads (spatial condition)and

● be stressed enough so that they break (energetic condition).

The mechanical division may beillustrated by comparing it withthe attempt to crack a nut with ahammer.

In order to break the shell, the nut must be hit in the firstplace (spatial condition), but itmust also be hit hard enough (energetic condition). For a proper understanding it is important to realise that bothconditions - spatial and energetic - must be fulfilled at the same time. Although thismodel may seem rather trivial, it clearly demonstrates the function of a dispersing machine.

In principle the validity of themodel can be proved with anydispersing instrument. For reaso-ns of simplicity, one should ima-gine a batch bead mill, filledwith a millbase which with

progressing state of dispersionillustrates a measurable changeof a technical property. Inpaints, this may for instance be the colour strength, the gloss,the viscosity or the fineness (to be measured with a HegmanGauge according to DIN53203). Our example usescolour strength. When all operating parameters, grindingbead filling quantity, bead type,speed, cooling etc. are keptconstant, the measured colourstrength reaches a finite valuerelated to the time ofdispersion. Longer dispersionwill not improve the colourstrength. Only by increasing the speed it is possible to furtherincrease the colour strength.

The reason for this behaviour isthat in a very long dispersion all agglomerates have theopportunity to get into the zonesof the maximum shearing effect.Those that are dispersed underthese conditions cause a visibleincrease in the colour strength.

Those that have such a high stability that they are not dividedunder the conditions of the maximum available shearingeffect, are still undispersed. By increasing the speed, zoneswith stronger shearing effectdevelop where more stableagglomerates can also bedispersed.Therfore, the colourstrength may continue to risewith increased speed.

Only after a sufficiently longdispersion time combined withsufficiently high speeds, can it be expected that all agglomerates are dispersed.Only then the spatial as well asthe energetic conditions requiredfor a full dispersion are met. Too low a speed can generallynot be compensated by longerdispersion and vice versa.


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Pass and re-circulationmethodIn principle, two methods can be distinguished in the operation of the DISPERMAT® SL bead mills.

Either, the complete millbase is collected after each pass through the bead mill (single or multiple pass), or else the millbase is fed directly back into the supply vessel from the outlet of the milling chamber (re-circulation method).

In the single pass method, the product is filled into a feed vessel and pressed through the milling chamber via continuouslyadjustable pneumatic transportsystem or with the feed press.

In the re-circulation method, the product is filled into the feed vessel and repeatedly pumpedthrough the milling chamber with an integrated, continuously adjustable pumping and stirringsystem.

The method of operation to bechosen depends on the type oftask. Easily dispersible pigmentscan often be processed with the single pass method, whereas with pigments that aremore or difficult to disperse there-circulation method is more efficient.

Over a period of time the re-circulation method ensures , that every agglomerate will get into a dispersion situation. Here, it has spatial and energetic condition and isdispersed. This means that there-circulation system is more efficient and economic.

pass method

re-circulation method

bead mill

bead mill

schematic view of pass and re-circulation method

Introduction to the dispersion technology withthe world wide patentbead mill DISPERMAT® SL


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Relationshipbetween PowerInput and Dispersion ResultBasic scientific research hasshown that the mechanicalpower that is transferred into the millbase is closely related to the dispersion result. The mechanical power determines the energy that istransmitted by the agitator viathe grinding beads to the product.The power P is calculated fromthe speed n of the agitator andthe torque M generated on the agitator according to the following equation:

Where:P power [Nm/s = J/s = W]

= 3,141...n speed [1/s]M torque [Nm]

The higher the energy density,the greater the probability thatmore stable agglomerates arealso dispersed.

It does not matter whether thepower input which leads to theexisting energy density, isapplied with a high speed and low torque or vice versa. With a given bead charge anddispersion time, the dispersionresult depends only on the amount of the mechanicalpower.

The torque therefore dependsdirectly on the flow characteristics of the millbase. If the viscosity changes duringdispersion at constant speed,the power input changes automatically.

If the viscosity decreases duringdispersion, the mechanicalpower drops, and if it increases,the mechanical power rises. Ifthe formulation is processed withmore cooling, the power input is higher, and with less coolingit is lower.

This for example, is the reasonwhy dispersion results may literally depend on the season,because in winter, the coolingwater may be much colder thanin summer!

The DISPERMAT® SL-C solves this problem by enabling themechanical power input fordispersion to be pre-set. Duringdispersion the torque of the rotoris continuously measured andthe speed controlled, so that the product of n and M leads toprecisely the pre-set mechanicalpower.Apart from the agitator geometryand the viscosity of the millbase,the torque transmitted by theshaft onto the millbase alsodepends on the type, quantityand size of the grinding beads.High bead filling volumesincrease the torque on the agitator shaft and also increase the probability that agglomerates come into a spatial dispersion situation.

P= 2 n M


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Steps to ImproveDispersion ResultsThe relationship between theeffects of energy and time enables the dispersion processto be optimised.

If the required dispersion result is not achieved, it must first bedetermined whether this can bechanged by increasing thedispersion time. The power input can be increased with higher speeds.This will normally improve thedispersion.Smaller and/or harder beads(e.g. zircon oxide or steel) canalso improve the dispersionresult. Further, the bead chargecan be increased to about 80%.In order to operate the bead milleconomically, dispersion shouldbe made with as much solidmatter as possible.If after the dispersion there issome flocculation, a suitabledispersing aid may help. A partial modification of the millbase formulation by usingmore suitable raw materialscan also be made.

How can the dispersion result beimproved ?● increased dispersion time

● increased speed

● increased mechanical power input

● improved cooling

● smaller or harder beads

● increased bead charge

● modification of the millbase (e.g. by using additives)

Introduction to the dispersion technology withthe world wide patentbead mill DISPERMAT® SL

DISPERMAT® SL-C EX, optional: double walled stainless steel supply vesselhl


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Transfer of LaboratoryTests to Industrial ProductionConsidering the many influenceson the spatial and energeticconditions of dispersion andtheir difference in various beadmills, it is not surprising to learnthat the transfer of the resultsfrom one machine to another isnot automatically possible. Evenif the same bead mill is used,but with different disks, the dwelltime distribution of the millbasewill be changed and, despitethe same number of passes(single pass) or same dispersiontime (re-circulation mode) the dispersion result will also change.

Nevertheless, if different beadmills are to be compared witheach other, it is generally thecase that production machineshave less adjustment possibilities. First, the typicalresult has to be determined on a known millbase.

With this typical result (e.g.fineness), a test series should be made with the DISPERMAT®

SL-M laboratory bead mill.Theimpeller speed should be adjusted and the dispersion continued until the result matchesthat which can be achieved inproduction.If a DISPERMAT® SL-C is available, the tests should bemade using mechanical powerinput.

When comparable results havebeen achieved, the settings onthe DISPERMAT® SL can be usedto determine results that are possible in production.

HintHere is WIN-DISP anexcellent tool for therecording and documentation of dispersion results.

When milling with constantpower input, not only can complicated dispersion processes be performed in a reproducible manner, but different dispersions can becompared exactly. The dispersion results from production machinery are easilyrepeated with the DISPERMAT®

SL-C and formulations workedout in the laboratory can betransferred into production.With the DISPERMAT® SL-C,problematic parameters like product temperature, coolingwater temperature or rheologicalbehaviour of the mill base, may be ignored as long as they do not reach limits criticalfor the product.


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Laboratoryand Pilot PlantBead Mills

Feeding Pressesand Accessories

Bead Mills

DISPERMAT®

SL-C EXDISPERMAT®

SL-C

DISPERMAT®

SL-M EXDISPERMAT®

SL-M

DISPERMAT®

RS 5RS 5 EX

FeedingPresses

Accessories

page 105

page 104page106-107

SoftwareWIN-DISP

page 22


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Bead Mills

DISPERMAT® SL

DISPERMAT® SL EX

DISPERMAT® RS 5

Software WIN-DISP

The DISPERMAT® range of horizontal bead mills includesinstruments for applications,including research and development, quality assuranceand production of larger quantities.

DISPERMAT® SL-C EX,with double walled supply vessel


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DISPERMAT® SL laboratory and pilot plant bead mills areclosed, horizontal bead millswith high output and extremelylow dead volumes in the millbase inlet and outlet pipes.During the dispersion process,the product to be dispersed isfed through the horizontal millingchamber and continuouslydispersed.The DISPERMAT® SL bead millscan be used for the pass as well as for the re-circulation process. After the dispersion,the integrated air pressuresystem presses the remainingmillbase out of the milling chamber which allows analmost complete recovery ofthe dispersed material.Due to minimised dead volumes,even the smallest quantities canbe dispersed with a high yield.

DISPERMAT® SL

Dispersion with Bead Mills

Therefore the DISPERMAT® SLis an ideal tool for Research,Development and Quality Control.Also, larger quantities can beprocessed within a very shortperiod of time. In order to minimise the product loss, themill base is transported directlyfrom the supply vessel into themilling chamber. The dispersedproduct passes through the millbase separation (dynamicgap) and is recovered either ina vessel (pass method) or flowsback into the supply vessel (re-circulation method).

● Quick and cost-effective development of new formulations through exact reproducibility of dispersions.

● Quick and reliable transfer of laboratory development into production because of quantitative knowledge of the required mechanical power input.

● Quality control and assurance of production.

● Efficient control of incoming raw materials by measuring product properties relevant for the application.

DISPERMAT® SL-C,optional: Stainless steel supply vessel

DISPERMAT® SL-M,optional: stainless steel double walled supply vesseland integrated pumping and stirring system


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Milling System● Milling system (stainless

steel milling chamber, nitride steel milling rotor)

● Millbase separation by dynamic gap

● Volume of milling chamber: 50, 125, 250, 500, 1000 and 2000 ml

● Master-batch from 50 ml to 50 l

● Shaft seal by means ofmechanical seal, built into easy to install cartridgesystem integrated, pressurised and cooled lubrication liquid

● Minimised dead volume

● Dispersion of small quantities of millbase is possible due to almost complete product recovery

● Very high millbase yield

● Excellent temperature transfer due to veined cooling water system with extremely large surface area

● Cooling water connections: two self-sealing fittings and twoquick couplers

● Milling beads of glass,zirconia etc.

95

Operation● Easy to use and secure

to handle

● Easy cleaning, allowing rapid change of material

Procedure● One-pass-procedure and

continuous pass procedure

● Circulation procedure with integrated pumping- and stirring system

● Dispersion of flowing and non-flowing products

● High mechanical power input permits processing of difficult to disperse systems

DISPERMAT® SL-M

● infinitely variable speed

● speed and temperature indication

Patented WorldWide DISPERMAT®

SL-CProcess Control● Excellent process

control through measurement andrecording of speed, power input, torque, work, product temperature and peripheral speed of the milling rotor.

● Operation with either: constant speed or constant power.

Option:● hard metal

● ceramic (ZrO2)

DISPERMAT® SL-C EX, optional: stainless steel double walled supply vessel

DISPERMAT® SL-M EX, optional: stainless steel double walled supply vesseland integrated pumping and stirring system


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Dispersing with Constant MechanicalPower Input - DISPERMAT® SL-C - Patented World Wide


Bead mills are used to disperse (finely divide) solidmaterial into liquid a phase. The actual dispersing systemconsists of a chamber and arotor; the chamber is filled withgrinding beads and the productto be dispersed.

While in conventional beadmills, the rotational speed is aneasily adjustable parameter, thetorque strongly depends on therheology of the mill base. Theseflow characteristics again stron-gly depend on the temperatureof the mill base. Therefore,during the course of a dispersionat constant rotor speed, the torque and the power input into the product changes in anuncontrolled manner.

With the world wide patentedDISPERMAT® SL-C the operatingparameters of speed, torque,power input and product temperature are continuouslymeasured and displayed. Operating at constant speed(conventional bead mills) provides information on thechanges in the other parameterswhich affect the milling process.

However, the most valuable insight into the dispersion process is only provided by operation with ”constant power input”.

Basic scientific research hasshown that the mechanicalpower that is transferred into the millbase is closely related tothe dispersion result. The mechanical power determinesthe energy that is transmitted bythe agitator via the grindingbeads to the product.

DISPERMAT® SL-Cwith stainless steel supply vessel


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The power P is calculated fromthe speed n of the agitator andthe torque M generated on theagitator according to the following equation:

P = 2 n M

Where:P power [Nm/s = J/s = W]

= 3,141...n speed [1/s]M torque [Nm]

It does not matter whether thepower input which leads to theexisting energy density, isapplied with a high speed andlow torque or vice versa. With a given bead charge anddispersion time, the dispersionresult depends only on the amount of the mechanicalpower.

The torque therefore dependsdirectly on the flow behaviour of the millbase. If the viscositychanges in a dispersion at constant speed, the power inputchanges automatically. If the viscosity decreases duringdispersion, the mechanicalpower drops, and if it increases,the mechanical power rises. Ifthe formulation is processed withmore cooling, the power input is higher, and with less coolingit is lower.

This for example, is the reasonwhy dispersion results may literally depend on the season,because in winter, the coolingwater may be much colder thanin summer!

The DISPERMAT® SL-C solves this problem by permitting themechanical power input fordispersion to be pre-set. Duringdispersion the torque of the rotoris continuously measured andthe speed controlled, so that the product of n and M leads toprecisely the pre-set mechanicalpower.

Compared with conventionalbead mills, the DISPERMAT® SL-C has manyadvantages in applicationswhere, exact reproducibility andprocess control are important,for instance in research and development, for checking incoming raw materials and inquality assurance.

When milling with constantpower input, not only can complicated dispersion processes be performed in a reproducible manner, but different dispersions can becompared exactly. The dispersion results from production machinery are easilyrepeated with the DISPERMAT®

SL-C and formulations workedout in the laboratory can betransferred into production.With the DISPERMAT® SL-C ,problematic parameters like product temperature, coolingwater temperature or rheologicalbehaviour of the mill base, maybe ignored as long as they donot reach limits critical for theproduct.

Dispersion with constant speed

time

torque

power

temperaturespeed

timetorquepower

temperature

speed

Dispersion with constant mechanical power

time

Dependence of the dispersion result onthe power input

P = 2 n M


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DISPERMAT® SL-M5 50 1,1 230/50 0 - 6000 50 - 500 ml

DISPERMAT® SL-M12 125 1,1 230/50 0 - 6000 100 - 750 ml

DISPERMAT® SL-M25 250 2,2 400/50 0 - 6000 200 - 2500 ml

DISPERMAT® SL-M50 500 3 400/50 0 - 6000 0,5 - 10 l

DISPERMAT® SL-M100 1000 3 400/50 0 - 3000 1 - 20 l

DISPERMAT® SL-M200 2000 4 400/50 0 - 3000 2 - 50 l

DISPERMAT® SL-C5 50 1,1 230/50 0 - 6000 50 - 500 ml

DISPERMAT® SL-C12 125 1,1 230/50 0 - 6000 100 - 750 ml

DISPERMAT® SL-C25 250 2,2 400/50 0 - 6000 200 - 2500 ml

DISPERMAT® SL-C50 500 3 400/50 0 - 6000 0,5 - 10 l

DISPERMAT® SL-C100 1000 3 400/50 0 - 3000 1 - 20 l

DISPERMAT® SL-C200 2000 4 400/50 0 - 3000 2 - 50 l

Type Milli

ng c

hamb

er

volum

e in

ml

Pow

er in

kW

Vollta

ge/

frequ

ency

in V/

Hz

Spee

d in

rpm

Reco

mmen

ded

millb

ase

volum

e


DISPERMAT® SL

DISPERMAT® SL-M, optional: stainless steel supply vessel,with integrated pumping and stirring system


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DISPERMAT® SL-MThe DISPERMAT® SL-M beadmills have an variable speedcontrol. The compact instrumentcontrol panel is convenientlylocated in the stylish housing.Speed and product temperatureare shown on a digital display.

DISPERMAT® SL-Cwith process controlmeasurement of:

● Speed (rpm)

● Power input (W)

● Torque (Ncm)

● Work (Wh)

● Product temperature (°C/°F)

● Peripheral speed of impeller (m/s, ft/min)

The DISPERMAT® SL-C enables a dispersion at either ”constantspeed“ or ”constant power“. The measured values are shownon a digital display. A serial port enables the data to be transmitted to a PC for processing with WIN-DISPsoftware (see page 22).

DISPERMAT® SL-C, optional: stainless steel supply vessel Software WIN-DISP


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DISPERMAT® SL-EX

The DISPERMAT® SL-EXlaboratory and pilot plant beadmills are designed for operationin areas where explosion proofequipment is required.

The main motor, as well as the control panel are explosion-proof.

Only the enclosure with the built-in power electronics is notexplosion-proof and has to belocated outside the hazardousarea.

Process technology ofthe DISPERMAT® SL-EXis the same as theDISPERMAT® SL.(see page 90-91)


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The designation of explosion-proof areasand correct choice ofequipment should be carried out by suitably qualified personnel or by the appropriate authorities.

DISPERMAT® SL-C EX, optional: double walled stainless steel supply vessel

Dispersion with constant speed

time

torque

power

temperature

speed

time

Dependence of the dispersion result on the power input

timetorquepower

temperature

speed

Dispersion with constant mechanical power

P = 2 n M


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DISPERMAT® SL-EX

DISPERMAT® SL-M EX, optional: stainless steel double walled supplyvessel, with integrated pumping- and stirring system

DISPERMAT® SL-M5 EX 50 1,1 230/50 0 - 6000 50 - 500 ml



DISPERMAT® SL-M50 EX 500 3 400/50 0 - 6000 0,5 - 10 l

DISPERMAT® SL-M100 EX 1000 3 400/50 0 - 3000 1 - 20 l

DISPERMAT® SL-M200 EX 2000 4 400/50 0 - 3000 2 - 50 l

DISPERMAT® SL-C5 EX 50 1,1 230/50 0 - 6000 50 - 500 ml



DISPERMAT® SL-C50 EX 500 3 400/50 0 - 6000 0,5 - 10 l

DISPERMAT® SL-C100 EX 1000 3 400/50 0 - 3000 1 - 20 l

DISPERMAT® SL-C200 EX 2000 4 400/50 0 - 3000 2 - 50 l

Type Milli

ng c

hamb

er

volum

e in

ml

Pow

er in

kW

Volta

ge/

frequ

ency

in V/

Hz

Spee

d in

rpm

Reco

mmen

ded

millb

ase

volum

e


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DISPERMAT®

SL-M EXThe DISPERMAT® SL-M EX explosion proof bead mills have variable speed control.

The compact instrument controlbox is conveniently mounted at the mill. Speed and producttemperature are indicated.

DISPERMAT®

SL-C EXwith process controlmeasurement of :

● Speed (rpm)

● Power input (W)

● Torque (Ncm)

● Work (Wh)

● Product temperature (°C/°F)

● Peripheral speed of impeller (m/s, ft/min)

The DISPERMAT® SL-C EX enables a dispersion at either ”constant speed“ or ”constant power“. The measured values are shown on a digatal display. An RS 232 serial port enablesthe data to be transmitted to a PC for processing with WIN-DISP software (see page 17-22).

DISPERMAT® SL-C EX, optional: stainless steel double walled supply vessel

Software WIN-DISP


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Accessories for the DISPERMAT® SL Bead Mill

FP and FP-EX FeedingpressesTo process high viscosity andnon-flowing materials with thebead mill, the feeding presssystem is required.

The feeding press with integralcontrol panel uses a pressurepiston to force the productthrough the milling chamber.

The DISPERMAT® SL supply vessel is removed and replacedwith a solid stainless steel vessel(capacity 500 ml or 1000 ml).

After pouring the material intothe vessel (if necessary, with aspatula), the press is attached to the vessel with a quick clamping ring. The lifting/lowering speed of the pressure piston can beinfinitely adjusted so that theflow rate of the material to beprocessed can be accuratelyset. When the piston reaches itslowest point, the press switchesoff automatically.The piston israised and the press is movedaside after loosening the quickclamping ring. If a foil is placedbetween the vessel and pistonprior to starting, the pressurepiston does not require cleaning.

FP 80 500 1 - 5 400/50FP 80 EX 500 1 - 5 400/50FP 100 1000 2 - 10 400/50FP 100 EX 1000 2 - 10 400/50

Type

Supp

lyve

ssel

volum

e ml

Flow

rate

ml/s

Volta

ge/

frequ

ency

in V/

Hz

Feeding press FP 80 EX


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Bead MillDISPERMAT® RS 5

The DISPERMAT® RS 5 is a horizontal bead mill for pilotplant and production applications. The compact, functional design ensures an extreme easy and safe handling as well as outstandingdispersing results.

● infinitely variable speed via modern frequency converter

● stirring shaft with double bearing is hollow for improved millbase heat transfer

● mechanical seal system with integrated cooled thermo-siphon container for lubrication liquid and safety pressure valve.

● adjustable dynamic gap bead separation system

● complete safety device

● simple central operation and control

● pressure control by manometer with electrical contact

● Non explosion-proof on request

● motor power: 15 kW

● speed: 0 - 2600 min-1

● milling chamber volume: 5 l

DISPERMAT® RS 5 C-EX

The DISPERMAT®RSis also availableexplosion-proofon request


function and task of the bead millfile.yizimg.com/362064/2013010415570082.pdfin principle, two...

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