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Significance and Use
5.3 Fine powders generally have a lower permeability than coarse bulk solids and therefore tend to retain air longer. Thus, when a bin is filled with a fluidizable powder, the coarser particles settle or are driven into the bed while the finer particles remain fluidized near the surface.
5.4 Fluidization, which serves as a driving force for this mechanism of segregation, is likely to occur when fine powders are pneumatically conveyed into a bin, the bin is filled or discharged at high rates, or if sufficient air flow counter to the flow of powder is present within the bin.
1.1 This practice covers an apparatus and procedure for creating several specimens of a powder sample that, if the powder is one that segregates by the fluidization mechanism, should be different from one another.
1.2 A powder sample is fluidized then, after the fluidizing gas is turned off, it is separated into three or more specimens that can be analyzed for parameters of interest. The difference in these parameters between the specimens is an indication of the segregation potential of the powder.
1.5 This standard is not applicable to all bulk solids and segregation mechanisms: while fluidization is a common segregation mechanism experienced by many fine powders, other segregation mechanisms not evaluated by this standard might induce segregation in practice. Practice D6940 covers another common mechanism: sifting.
1.6 The extent to which segregation will occur in an industrial situation is not only a function of the powder and its tendency to segregate, but also the handling equipment (for example, bin design), process (for example, transfer rates), and environment.
1.8 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project’s many unique aspects. The word Standard in the title of this document means only that the document has been approved through the ASTM consensus process.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
D6940 Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
ICS Number Code 19.120 (Particle size analysis. Sieving)
ASTM D6941-12, Standard Practice for Measuring Fluidization Segregation Tendencies of Powders, ASTM International, West Conshohocken, PA, 2012, www.astm.orgBack to Top