Centrifugation Disc centrifuges

Tubular centrifuge Multichamber centrifuge Imperforate basket centrifuge Scroll-type centrifuge Disc centrifuge... 

The complete filtration apparatus is shown in Fig. 5, p. 11. A simpler and cheaper apparatus is shown in Fig. 45. This consists of a boiling-tube A having a side-arm for connection to the pump the tube A is conveniently held in a wooden or cork block B or in a clamp. The funnel F may be fitted into A through a pliable rubber disc D the latter is more useful than a cork since it covers tubes of various diameters. The filtrate is collected in the centrifuge-tube T. 

A Pyrex micro filter (Fig. XII, 2, 18) of 8 ml. capacity and furnished with a sintered glass disc is useful for the filtration of hot or boihng hquids. The long cylindrical tube reduces evaporation. The filter may be inserted into a test-tube with side arm (Fig. XII, 2, 13) and the filtrate collected in a centrifuge tube or semimicro test-tube receiver. 

The disc centrifuge, developed by Slater and Cohen and modified by Allen and Svarovsky [Allen and Svarovsky, Dechema Monogram,... 

Several centrifugal cuvet photocentrifuges are commercially available. These instruments use the same theoiy as the disc photocentrifuges but are hmited in operation to the homogeneous mode of operation. 

The X-ray disc centrifuge is a centrifugal version of the gravitational instruments and extends the measuring technique well into the sub- Im-size range. 

These are an itnprovised version of a totally enclosed motor to protect its live parts from ingress of water, rain, snow or airborne particles etc. This is achieved by providing them with additional protection such as labyrinths at joints such as bearing end covers, centrifugal discs, end shields and terminal box and giving the outer... 

Centrifugal compressors can have problems at the inducer and blade tips. These parts of the blade can be excited by aerodynamic forces. Blade discs can have stresses at the rotor tips, which lead to cracks. To solve this problem, the offending part is removed and a scalloped disc results as seen in Figure 21-20. This type of disc experiences some efficiency loss (about 2 %). 

The impellers for centrifugal compressors are assemblies consisting of three parts the hub disc, the blades, and the cover disc. The hub and cover disc are machined from single-piece forgings of an alloy steel suitable for the application of the compressor. Blades are machined from forged steel plates of identical material. Each forging is checked with either sonic or X-ray machines to detect flaws or inclusions. 

Microbial cell recovery is carried out in a continuous disc-stack centrifuge. The centrifuge is operated at 5000 rpm for separation of baker s yeast. At a feed rate of 601/min, 50% of the cells are recovered. At constant speed, solid recovery is inversely proportional to flow rate. 

Figure 2, Top view of the miniature centrifugal analyzer. The sample disc, not shown, fits on the rotor holder and can process 16 samples and 1 reference simultaneously, (Courtesy of Dr, Carl A, Burtis),...

An area worthy of study is the development of systems of increasing sample throughput beyond the single column operation. Scott has introduced a prototype multicolumn system based on the centrifugal analyzer principle (53). In this set-up a series of LC colimns is rotated on a disc, with sample delivery at the center of the disc and elution and spectrophotometric analysis on the outside. He has suggested using affinity columns for rapid serum protein analysis by this approach. Of course, other principles, such as segmented flow, could be envisioned in an automated LC system as well. Undoubtedly, we can expect to see the availability of such systems in the next few years. 

Centrifuges are used for the classification of particles in size ranges below 10 /im. Two types are used solid bowl centrifuges, usually with a cylindrical, conical bowl, rotated about a horizontal axis and nozzle bowl machines, fitted with discs. 

The conical discs in a disc bowl centrifuge split the liquid flow into a number of very thin layers, which greatly increases the separating efficiency. Disc bowl centrifuges are used for separating liquids and fine solids, and for solids classification. 

An unknown event disturbed the equilibrium of the interstellar cloud, and it collapsed. This process may have been caused by shock waves from a supernova explosion, or by a density wave of a spiral arm of the galaxy. The gas molecules and the particles were compressed, and with increasing compression, both temperature and pressure increased. It is possible that the centrifugal forces due to the rotation of the system prevented a spherical contraction. The result was a relatively flat, rotating disc of matter, in the centre of which was the primeval sun. Analogues of the early solar system, i.e., protoplanetary discs, have been identified from the radiation emitted by T Tauri stars (Koerner, 1997). 

Assuming laminar flow to the rotating electrode surface, i.e. the rotation rate is not sufficiently fast to cause turbulence, Karman and Cochran solved the pattern of flow and showed that the streamlines are as in Figure 2.89. The rotating disc sucks solution up towards it from the bulk and flings it out centrifugally. The layer of liquid immediately adjacent to the surface is... 

Methods for making both forms solvent-soluble were the subject of many patents and closely guarded industrial secrets, but much of the mystery was cleared up in two papers by Gerstner [23] and Smith and Easton [24] published in 1966, by which time X-ray diffraction, electron microscopy and disc centrifuge particle sizing methods had been brought to bear on the problem. 

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