Roller elutriator

Figure 5.5. Data and performance of the Roller elutriator. (The nominal range of the fractions are indicated by the dashed vertical lines.) a) Sketch of the Roller elutriator. b) Performance data for (i) Less than 5 micron fraction (ii) 10 to 20 micron fraction, c) Performance data for (i) 20 to 40 micron fraction (ii) 40 to 80 micron fraction. 9) Performance data for greater than 80 micron fraction.

The Roller Elutriator is available from the American Instrument Company, 8030 Georgia Avenue, Silver Spring, Maryland, USA. 

The essential differences between the two types of elutriators are as follows Roller s type requires a small quantity of dust which must be vibrated continually in the U-tube so as to bring it in contact with the air jet. The author s technique permits the use of large quantities of material and secures more rapid separation. Both devices can produce sharply defined size-distributions. 

Experimental Results—Gottschalk and Wartman (loc cit) investigated the properties of a number of magnetite powders. Magnetites from four sources were purified and sized, each size-fraction then being analyzed for FesC>4. Only size-fractions below 100-U. S. mesh were studied. Sizes below 350-mesh were air elutriated by the Roller method. 

The circulating type of elutriator, as developed by Roller is similar to the up-blast but the sample of powder is caused to circulate in a U-tube at the base of the elutriator tube. The elutriator has four chambers, to each of which is attached a paper extraction thimble collector for the fines. Ancillary equipment, including mechanical rappers, is included and the instrument is contained in a sound proof cabinet. 

The sample tube in the original Roller analyzer was a U-tube attached at one end to the bottom of the elutriation chamber, and the catalyst was blown into the chamber by means of a high-velocity air jet (over 200 ft. per second). It was found that some attrition occurred during analysis, particularly with fresh ground catalyst. To avoid this difficulty, a modified sample tube was developed that consists of a straight cylinder fitted with a porous sintered metal disc at the bottom (206). The sample tube containing the weighed catalyst is attached to the bottom of the elutriation chamber, and air is introduced below the porous disc. 

Sedimentation methods are also useful in determining particle size distribution. Webb (28) describes the techniques employed in liquid sedimentation and gives data comparing the results with those obtained in mechanical screening. Sedimentation methods are particularly useful in measuring sub-sieve sizes. Air-elutriation methods (Roller, 29) are also useful, especially when used in connection with microscopic examination (Wiley, Deloney, and Denton, 30 Matheson, 31). 

Roller Elutrlator. An air-type elutriator designed for the determination of fineness of portland cement. (P. S. 

This part covers air elutriation methods, such as the Gonell, the Roller (modified ASTM), and the miniature elutriation methods. As these are rarely, if ever, used for particle size distribution determination nowadays, it is likely that this Standard will be withdrawn. 

---