Subsieve Sizer, Fisher

Two types of instruments are employed to determine the specific surface area by permea-metry. Those of the first type are called constant pressure systems, and the Fisher subsieve sizer is a typical example that belongs to such systems. Instruments of the second type are known as constant volume permeameters, and the apparatus devised by Blain is an example. 

Mean particle size, pm (Fisher subsieve sizer) 0.65 1.88 1.02 2.2... 

H) Particle Size. Det it by meansof a "Fisher Subsieve Sizer"(Ref 4,p 848), in accordance with manufacturer s instructions... 

Average grain size as supplied Fisher Subsieve Sizer ASTM No. B 330-88... 

Average particle size. The average particle size (APS) of the powder is the main parameter for WC powder classification. It is obtained by Fisher Subsieve Sizer measurements and is commonly given both as as-supplied and lab-milled, according to ASTM standard procedures (ASTM B330, and 430 see also Chapter 5 Table 5.12). 

Sodium nitrate was 55 microns by sieve, 20 microns by Fisher subsieve sizer. 

Carman showed that for many materials the constant B, could be taken as 5. However, Carman stated clearly that the universal use of the value 5 will lead to error in certain cases [6, 7]. Because of the lack of alternative values, however, commercially available permeameters such as the Fisher Subsieve Sizer are calibrated for operation on the assumption that the value B = 5 is used in the Kozeny-Carman equation [8]. The unknown value of B for any specific powder is an immediate source of discrepancy between the surface area measured by permeability with that measured by other techniques. The only way to determine B exactly is to use an independent method of analysis to measure the surface area of the powder. B is sometimes called a tortuosity factor but it is my opinion that it is better to call the factor B a correlation factor and in this way firmly state the true nature of the adjustment being made to the equation. 

Figure 9.3. Pioneering designs of permeameters used to measure the Bneness of powders led to a widely used commercial instrument known as the Fisher Subsieve Sizer, a) The Lea and Nurse permeameter. b) The Gooden and Smith permeametcr used a column of fine sand as a standard resistance, c) The Fisher Subsieve Sizer uses a standpipe in a column of water to provide a constant pressure head.

Fisher Subsieve Sizer is made by Fisher Scientific Co., 633 Greenwich St. New York 14, N. Y. and is no longer available commercially. 

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