06 planetary mixers construction equipment

8/3/2019 06 Planetary Mixers Construction Equipment

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6 Planetary Mixers 68

6 Planetary Mixers

6.1 Review

Planetary mixers are mainly used to mix medium viscous to high viscous medias, i. e.liquids, pastes, creams, suspensions or dry powder mixtures, which are being processedin the chemical, pharmaceutical, cosmetic and food industry.

There are planetary mixers for laboratory requirements with bowl sizes from 2 litres up aswell as for production purposes with more than 1250 litres. Furthermore existing bowls

can be fitted with a top mounted planetary mixer as an addition.

An optimal mixing is achieved by the characteristic movement of the mixing tool. Thismoves on a circular path and at the same time around its own axis and in addition awall scraper moves along at the same time. This way no dead zones exist in the mixingbowl which results in guaranteeing a thorough mixing even at low revolutions and littleenergy needed. This is of highest importance for instance with shear sensitive products.

Up to now a double planetary mixer had to be operated when the effect of specific shearforces on the mixing product was needed. Today there is a cost saving alternative. Anewly developed mixing tool provides an optimal adjustment of the shear force to the

product by means of a variable slot width.The shear of a planetary mixer normally is not sufficient for the production of fine dis-persed emulsions. A Rotor-Stator-System (Homogeniser) provides the necessary forces.The product is drawn out of the bottom valve of the mixing bowl then axially sucked inby the homogeniser and radially pressed through the slots of the rotor-stator-system. Theproduct is then pumped back into the mixing bowl through the outside pipes.

The intensity of the shearing strain can be influenced by adjusting the slots and thespeed. The use of the homogeniser can be extended considerably by adding a productpump prior to the entry into the bowl. The possibility of a dust-free dosage of powdersinto the rotor-stator-system also is of advantage.

An almost continuous operation is obtained by using several mixing bowls. While stirringtakes place in one bowl, a second bowl can be emptied, cleaned and refilled. This reducesthe operating cycle considerably so that the production rate can be increased or seasonalfluctuations can be controlled. In most cases this alternative is more economical than theoperation of a larger mixer.

If requested, all planetary mixers can be equipped with a jacketed bowl with electricheating, a vacuum installation and further accessories.

All machines parts in contact with the product are normally made of stainless steel.

Special materials or surface coatings, such as Hastelloy, Teflon, etc. are also possible, aswell as mixers suitable for use in explosion zones (ATEX 94/9).

The suitable electronic control technology - from control cabinet to fully automatic control- is also available. The standard of the machines complies with the regulations of BGChemie and GMP/FDA regulations.


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6.2 Construction Types 69

6.2 Construction Types

One differentiates between three different models, up-right support construction, standconstruction and the planetary mixer with hydraulic lifting column.

Figure 45 shows the planetary mixer in its classic tripod construction. A normal bowlcapacity ranges from 7 to 120 litres. A typical aspect is that the bowl can be moved upand down whereas the mixing head with the drive is stationary.

Figure 45: Vacuum Planetary Mixer HRV 50 in up-right support construction

With regard to the stand construction of the mixer it is possible to move the main driveunit, which consists of the bowl cover, the stirrer drive and the stirrer devices, up anddown. As a rule the bowls are fitted with rollers; sometimes they are equipped withsuitable lashes for fork lift trucks. There are three alternatives with stand mixers: thewall stand, the floor stand and the mobile stand. Figure 46 shows the planetary stirrerwith wall fixing.

Figure 47 shows a 120 litres planetary mixer combined with a rotor-stator-system (Ho-mogeniser). This new construction is available for a bowl capacity of 100 to appr. 1500litres.

The lifting column of the mixer which lifts the complete head with drive and stirrer toolshydraulically represents a new development. Disadvantages of a folded coat respectivelygrease lubrication are being avoided by a dry running lifting column. A specially simple


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Figure 46: Planetary Mixer HRV-S 120 in stand construction

Figure 47: Planetary Mixer HRV-K 120 HO with hydraulic lifting column


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and effective cleaning of the complete mixer is possible in combination with the smoothstainless steel surface of the machine housing. It stands to reason that also the mixingspace which has contact with the product as well as the stirring tools are constructedeasy-to-clean. After lifting the drive head the bowl, which is fitted with rollers, can bemoved to other parts of the site.

These two construction types are being used specially with larger bowl capacities becausethe bowl does not need lifting.

6.2.1 Product Models HR-S 2 to HR 10

The planetary mixers HR-S 2 to HR 10 are designed for use in laboratories and smallproduction runs. The effective mixing volume lies approx.. between 0,4 and 1,6 litres forthe planetary mixer HR-S 2 and between 2,0 and 8,0 litres for the planetary mixer HR10.

The stainless steel mixing bowl of the planetary mixer HR-S 2 (see Figure 48) is eithersingle or double jacketed with a volume of 2 litres. By using a glass mixing bowl, themixing process can be viewed through the glass jackets which is especially advantageousin the research and development field.

Figure 48: Planetary Mixer HR-S 2a) stainless steel mixing bowl, b) glass mixing bowl

The driving unit with the planetary gear is fixed on top of the mixing bowl cover. The leveladjustment of the cover is manual; for weight equalisation purposes a counter weight isinstalled on the inside of the column. Alternatively the level adjustment can be regulatedelectrically by a linear drive.


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Starting with the large planetary mixing unit, all known standard mixing tools can beused for stirring purposes; complete with a wall scraper made of Polyamide, Teflon orstainless steel.

A double jacketed bowl can be cooled respectively heated by an external system. Theunit can also be equipped for vacuum operation.

The support column, floor plate and all parts in contact with the product, with theexception of the scraper, are of stainless steel construction. The bowl cover and the driveunit are, for weight reasons, made of aluminium.

Figure 49 shows a 7 litre vacuum planetary mixer unit HRV 7. The bowl is fixed to the

Figure 49: Vacuum Planetary Mixer HRV 7

vacuum cover by means of a bayonet lock. An illuminated sight glass fitted with a wiperpermits observation of the mixing process.

An especially user friendly design of a stand construction is shown in figure 50. The doublejacketed, electrically heated, bowl is fitted onto the stand base plate. The complete mixinghead can easily be manually lifted by means of the guides fitted with ball bearing anda counter weight in the stand column. A hydraulic, electrical or pneumatically operatedlevel adjustment can also be provided. Figure 63 on page 84 shows a 3 litre vacuum-planetary mixing unit with an electric level control.

The 7 litres planetary mixer is fitted with a protection hood. The speed is controlled bya mechanical control gear and not by a frequency transformer.

A customised basis standard version of the mixers as illustrated in figure 51 can befitted onto a mobile stainless steel trolley together with a 2 ltrs. vacuum planetary mixerand an external heating/cooling system.


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Figure 50: Planetary Mixer HR-S 7

Figure 51: Vacuum Mixing Plant HRV-S 2


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6.2.2 Product Models HR 15 to HR 120

These planetary mixers are designed foremost for use in production units, but are also

suitable as laboratory units. The available mixing capacity is between approx. 3 and

100 litres. These mixers can be constructed as classic stand version or the more versatile

stand model. Figure 27 shows a 15 l vacuum planetary mixer with homogeniser HRV 15

HO as a classic version. Figures 45 to 47 show design variations.

Figure 52: Vacuum Planetary Mixer with Homogeniser HRV 15 HO

6.2.3 Product Models HR-S 100 to HR-S 1250

These planetary mixers are designed foremost for use in production units. The available

mixing volume varies between approx. 20 to 1000 litres. These mixers are designed as

free standing mixer units, but are also optionally available as wall or floor mounted units.

The free standing version with an integrated lifting column and a mixing bowl volume of

up to 500 litres is also available.

Figure 53 shows a free standing planetary mixer. The complete drive unit is electro-

hydraulically lifted to permit the removal of the mixing bowl after termination of the

mixing process.


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6.3 Customised Designs 75

Figure 53: Planetary Mixer HR-S 400 (stand construction)

6.3 Customised Designs

6.3.1 Double Planetary Mixer

Where higher shear force entry is required in the mixing process, a special mixing tool(see also chapter 6.4.4) or a double planetary mixer can be used. The special design andposition of the two mixing tools provide the necessary shear forces for a free revolutionand an effective mixing operation. The level of the shearing strain is dependent upon therotating velocity and the clearances between the mixing tools.

6.3.2 Detachable Planetary Mixer

Suitable bowls can be retrofitted with a detachable planetary mixer. The planetary mixerunit would then be attached to the centrally located bowl flange.

6.3.3 A Combination of a Planetary and a Central Mixing Unit

In the research and development field it is often of great importance to cover the largestpossible functional range with only one mixer. To achieve this the planetary mixer canbe fitted with an additional connection for a central agitator shaft.

Figure 54 shows a combination of a planetary gear with a central agitator shaft. On theleft is the planetary gear with the planetary mixing tool and wall scraper, the centrallylocated drive spigot for the agitator is clearly visible.


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6.4 Machine Technique 77

Figure 55: Planetary Mixer with additional Central Agitator Shaft HR-S 15-40 Z

Figure 56: Plotted point of a Planetary Mixing Tool


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Figure 57: Construction of Planetary Gear

The standard design does not provide an absolute separation between the product areaand the transmission interior (see fig. 57). This disadvantage is eliminated by the totalencapsulation of the planetary gear. Total enclosure is ensured by the installation ofstandard seals (see also centrally mounted mixers) or the use of slip rings. The use ofquick-release couplings allows for a quick and trouble free exchange of the various mixingtools.

6.4.3 Equipment Design

Planetary mixers are normally fitted with a variable speed adjustment. The speed adjustment can either be reached by a frequency converter or a mechanical variable speedgear box.

The level of the mixing bowl for stand mounted planetary mixers is normally adjustedhydraulically, however, a number of mixer types have the possibility of a hand or footoperated hydraulic adjustment.

The mixer bowl and the planetary mixer head are built as a correlated unit to ensure thecorrect all clearance between mixing bowl, mixing tool and wall scraper. The scrapersare usually of either Polyamide or Teflon and are pressed onto the bowl jacket by theproduct during the mixing process, thus preventing product adhesion. A stainless steelscraper can be supplied but this requires a manual adjustment to provide the necessarywall clearance.


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Single or double jacketed bowls can be supplied. Jacketed bowls are usually fitted withelectrical heating elements which heat the transfer medium (water or thermo-oils). Thetemperature is controlled by a thermostat. By operating temperatures above 60 Cadditional insulation around the mixing bowl must be fitted. Operating temperatures ofabove 90 C and up to above 200 C require a thermo-oil as heating medium. Externalheating/cooling unites or steam heating, complete with the necessary safety precautions,may also be used.

It is recommendable to install an additional heating/cooling coil in the jacket should itbe necessary to heat or cool the product during mixing.

The temperature indication of the vessel jacket does not present a problem, however, theproduct temperature indication is a different matter. There are a number of possibilities,i. e. the temperature element may be fitted into a tube which penetrates the inside jacketof the bowl, or is extended into the bowl which then requires the wall scraper to be cutout to the extent of the thermometer.

In case of planetary mixers with homogeniser the temperature element may be mountedinside the bottom discharge of the mixing bowl as the total product is circulated duringthe homogenising operation.

Both described mounting methods have accuracy problems. Should correct product tem-perature control during the mixing operation be essential then the installation of a tem-

perature element on the mixing tool itself is the optimal method as the measurementvalues are transferred by infrared technology; alternatively a slip ring transmitter withhigher temperatures can be installed (see section 3.5.2, page 24).

6.4.4 Mixing Tools

Figure 58 shows some standard planetary mixing tools.

The fitting of a quick release coupling allows for a trouble-free change of mixing tools tosuit the specific need of various products.

Figure 58: Standard Planetary Mixing Tools

Form F1 is often used to stir creams, ointments and pastes, F2 for light substances, F3 forsolid substances and powder mixtures. Form F4 is used to process emulsions and foams.


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The stirring tool F4 is also applicable for a double planetary mixer and so is F5, whichcan be used for solid and viscous products.

The straight-arm paddle agitator F5 can be combined with the shearing frame F5.1.

This frame is fixed to the mounting support for the scraper. The stirring tool will comb

through this shearing frame at every revolution. The result can be compared to the

one of a double planetary mixer, whereas the relative speed between the stirring tool

bars is lower. The value of the transferable shear forces depends also on the fixed slot

width and the revolutions, and this money saving alternative is mostly sufficient for many

applications.

The planetary stirring tool F6 is specially suitable for stirring oil-in-water-emulsions.Specific designs can also be provided in addition to the standard mixing tools application.

Figure 59 shows a helical stirrer.

Figure 59: Helical Planetary Mixing Tool


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6.5 Application Examples 81

6.5 Application Examples

6.5.1 Vacuum Laboratory Mixing Unit HRV-S 2-ex

A further development of the vacuum mixing unit HRV-S 2 (figure 51) is illustrated inFigure 60. The mixing unit is housed in a stainless steel cabin with two wing doors. The

Figure 60: Vacuum Laboratory Mixing Unit HRV-S 2-ex

cabinet of the Ex-zone 1 construction is located in a non Ex-proof area. Operation ofthe mixing unit is only possible with doors closed. The large glass windows in the doorsenable a perfect sight of the mixing process inside. The cabin interior is vented by anexternal exhausting system in order to remove solvent vapours.

The vacuum pump, the circulation thermostat and the main control box as well as thecontrol panel are located outside of the cabinet.

The special construction of the mixing unit permits the selective operation of the high-speed central mixer or the low speed planetary mixer. The fitted guide rail allows forhorizontal movement of both mixing units. The integrated counterweight permits an easyvertical movement of the mixer driving gears.


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In addition, the mixing unit is fitted with a simple bowl discharge device. The build-indischarge aid, shown on the right side ofFigure51, which is manually operated by means of

a threaded spindle. This discharge aid permits the product paste to be discharged directly

from the mixing bowl into a double chamber cartridge for which a special acceptance

device has been integrated.

6.5.2 Vacuum-Double-Planetary Mixing Unit HRV-S 2 DP

Figure 61 shows the Vacuum-Double-Planetary Mixing Unit HRV-S 2 DP used in the

production of dental compounds.

The elevation adjustment of the mixing heard by manual means is assisted by the instal-

lation of a counter weight housed in the support column and the carriage is mounted on

ball bearings.

Figure 61: Vacuum-Double-Planetary Mixing Unit HRV-S 2 DP

Employed are intertwine operating mixing tools of a straight-arm agitator design. Allparts as well as the internal jacket of the bowl, which are exposed to the product, are

coated with polyamide.


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6.5.3 Vacuum Double Planetary Mixer HRV-S 2-4 DP

The planetary mixing unit shown below in figure 62 is fitted with a double jacket glass

bowl. This bowl enables the product to be cooled with water and allows easy observation

Figure 62: Vacuum Double Planetary Mixer HRV-S 2-4 DP

of the mixing process, ideally suited for development work.

The possible use of two different bowl sizes allows for a wider range of applications.

6.5.4 Vacuum Planetary Mixer HRV-S 3

The vacuum planetary mixer, shown in figure 663, is used in the process development of

new tooth past recipes and in trial operation. The stainless steel bowl, which is mounted

on the base plate of the stand, has a volume varying between. 0,6 to 2,4 litres. An

electrically driven linear gear is installed to control the level adjustment of the machine

head.

6.5.5 Vacuum-Planatary Mixer HRV-S 7

The Vacuum-Planetary Mixer in image 64 is used for the production of gels. The single


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jacket bowl is fixed on the stand floor plate. The level adjustment of the machine head ismanual. The mixing process can be observed through a sight glass.

The machine cover is designed for the operation with different bowl sizes, whereby onlythe mixing tools and the bowl scraper have to be exchanged.

6.5.6 Planetary Mixer HR-S 25

Figure 65 shows the stand version of a basic planetary mixer. The 25-liter bowl is fitted

Figure 65: Planetary Mixer HR-S 25

with a trolley. The height of the machine is manually adjustable.

6.5.7 Vacuum Double Planetary Mixer HRV-K 30 DP

The characteristics of the planetary mixer (figure 66) show the two separate drive units,which allow the operation of the slow rotating planetary stirrer without being dependenton the high-speed dissolver. The two drive units have an independent variable speedadjustment, as required by the product mix.


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Figure 66: Vacuum Double Planetary Mixer HRV-K 30 DP

If selective high shear forces are required for a product mix, these can be provided by adissolver. The planetary mixing tool provides well blended product mixes even at highestviscosity.

The insulated jacket bowl is fitted with a screw-mounted electric heating element for theheating media; with water as heating medium a product temperature of 90C can berealized. A vacuum pump for vacuum operation is provided.

The complete mixing unit is designed for easy cleaning. Cables are installed in one of thetwo lifting columns.

6.5.8 Vacuum Double Planetary Mixer HRV 40-60 DP

A double planetary mixing unit is shown in figure 67.

This unit is intended for mixers fitted with 40 or 60 litre mixing bowls. The two mixingtools interlace with each other, whereby the straight arm model (form F5) also providesan upwards flow of the product. In addition a wall scraper is fitted which moves theproduct from the jacket to the centre of the bowl.

The planetary mixer is used for the production of highly viscose pastes.


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Figure 68: Planetary Mixer HR-S 100 with tiltable Mixing Bowl


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Figure 69: Doppelplanetenruhrwerk HR-S 120 DP

The control technique, which is integrated in the control cabinet, enables the projectingof different process parameters and the course of a fixed mixing process and is operatedby a touch panel.

6.5.11 Vacuum-Planetary Mixing Unit with Homogeniser HRV-S 500 HO

This mixer is designed for use in the manufacture of biologically based cosmetics (seefig. 70). The design allows for vacuum operation, an inline homogeniser and an infrared

product temperature transmitter.

The mixer is of free standing, floor mounted design additionally fitted with wall mountingsupport installations. The electrically heated jacketed bowl is fixed to the base plate.

6.5.12 Vacuum-/Pressure Planetary Mixer Unit HRVD-K 700 HO

The mixer unit shown in fig. 71 can be operated either under vacuum or pressure. Theelevation of the mixing head is hydraulically adjustable. The lifting carriage supportcolumn is non-lubricated (dry-running). Three CIP sprinkler heads are mounted on the

bowl cover which considerably ease the internal bowl cleaning operation, further assistanceis provided by circulating the cleaning fluid with the homogeniser.


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Figure 70: Vacuum-Planetary Mixing Unit with Homogeniser HRV-S 500 HO

Figure 71: Vacuum-/Pressure Planetary Mixer Unit HRVD-K 700 HO with Homogeniser


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6.5.13 Double Planetary Mixer HR-S 1000 DP

The double planetary mixer HR-S 1000 DP, as shown in figure 72, is being used by thepharmaceutical industry for mixing predominantly dry substances. Special emphasis hasbeen placed on an easy cleaning of the mixing unit. Furthermore, CIP-spraying heads arefixed to the bowl hood.

The mixing unit is fitted with two single jacketed bowls, which allow virtually a continuousoperation. The bowls are transported by a special bowl carriage, which may, if so required,be fitted with a lifting/tilting device.

Figure 72: Double Planetary Mixer HR-S 1000 DP

06 planetary mixers construction equipment

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