Hermetic centrifuges

Continuous product flows under high-pressure conditions (p > 30 MPa) can only be achieved with hermetic centrifugal pumps. Although the two drive systems that can be used - the permanent magnet coupling and the asynchronous canned motor - have the same mode of operation, they differ in their applications and their safety ranges. 

Hermetic centrifuges may be used in pressure systems up to 8 bar in situations where ... 

In breweries, for example, hermetic centrifuges can be used for pre-clarification of beer ready for packing, with no carbon dioxide losses and no destruction of protein for the clarification of the cold wort, with a good clarification efficiency because protein particles are not destroyed. In dairies, hermetic centrifuges are used because milk is sensitive to both oxidation and shear. 

Figure 11-21B. Packaged hermetic open drive two-stage centrifugal liquid chiller with flash economizer. (Used with permission Cat. 521-727, 1995. Carrier Corporation, a United Technologies Company.)...

Centrifugal machines can be built for industrial use with ammonia and other refrigerants, and these mayhave up to seven compression stages. With the high tip speeds in use, it is not practical to build a small machine, and the smallest available centrifugal compressor for refrigeration dutyhas a capacityof some 260 kW. Semi-hermetic compressors are made up to 7000 kW and open drive machines up to 21 000 kW capacity. 

Fig. 4.1-27. Ten-stage canned-motor centrifugal pump (HERMETIC)...

Hermetic canned motor centrifugal pumps in high-pressure processes... 

Fig. 10 Single-stage, semi-hermetic high-pressure canned-motor centrifugal pump...

Self-cleaning clarifiers, in which the solids are discharged at intervals while the centrifuge is operating at full-speed (Fig. 20.12). They are available for both wort and beer clarification with throughputs of up to 600 hl/hr (370 brl/hr). The same machines used for beer recovery from fermenters and tank bottoms operate at up to 40 hl/hr (25 brl/hr). Many of these machines used for beer treatment are hermetically sealed so that neither carbon dioxide is lost nor oxygen taken up. 

The advantages of centrifuges are (/) small requirement for space, (//) they can be sterilized and maintained sterile, in) there is no requirement for kieselguhr of other filter aids, (/v) using hermetic clarifiers there is no contact with air, (v) there is no removal of material by adsorption to active surfaces. 

Cast iron or steel pumps are recommended and can either be centrifugal, hermetic or those operating with solvent resistant mechanical seals. All vessels and intake lines, marked at the delivery point, should be clearly labelled with the name of the solvent. Regular, recorded inspection should be undertaken to ensure the integrity of the storage tank, pipes and pumps. 

Design of centrifugal pumps. As with reciprocating pumps there is a choice between the leakfree (hermetic) and the shaft-sealed designs for centrifugal pumps. 

Fig. 10, - Chaos ( hyle or pan ) is understood as a mixture of backwash elements (left) confused by the inherent light of heat against cold and humidity against dryness. Crucial effect of the central sun helped to disperse chaos and the four elements became organized in the concentric circles (right) around the sun in the middle, which is followed by fire (as the most powerful rudiment) and then by air, water and earth. On contrary, in the hermetic conception the central position upholds the earth with water above (as the retractile force JIN) and the outer spheres are fulfilled by air and fire (far away stars as blaze perforations in the firmament) represenling the centrifugal force (JANG).

At this time the only pumps considered capable of meeting these requirements are of the hermetically sealed canned-motor centrifugal type. They consist of a centrifugal pump of standard hydraulic design and an electric drive motor, built in an integral unit. 

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