ASTM D6940-10
(Practice)Standard Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
Standard Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
SIGNIFICANCE AND USE
Sifting segregation can cause horizontal segregation (for example, center-to-periphery) within bins used to hold and transport bulk solids. This can affect final product quality in industrial applications.
By measuring a bulk solid's segregation tendency, one can compare results to other bulk solids with known history, or determine if the given bulk solid may have a tendency to segregate in a given process.
Sifting, which is a process by which smaller particles move through a matrix of larger ones, is a common method of segregation. Four conditions must exist for sifting to occur:
A Difference in Particle Size between the Individual Components—This ratio can be as low as 1.3 to 1. In general, the larger the ratio of particle sizes, the greater the tendency for particles to segregate by sifting.
A Sufficiently Large Mean Particle Size—Sifting segregation can occur with a mean particle size in the 50 μm range and can become a dominant segregation mechanism if the mean particle size is above 100 μm.
Sufficiently Free Flowing Material—This allows the smaller particles to sift through the matrix of larger particles. With cohesive materials, the fine particles are bound to one another and do not enter the voids among the coarse particles.
Interparticle Motion—This can be caused during formation of a pile, by vibration, or by a velocity gradient across the flowing material.
All four of these conditions must exist for sifting segregation to occur. If any one of these conditions does not exist, the material will not segregate by this mechanism.
Note 1—The quality of the result produced by this practice is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this practice are cautioned that compliance with Practice D3740 does not in itself assure...
SCOPE
1.1 This practice covers an apparatus and procedure for simulating the segregation tendencies of bulk solids by means of the sifting mechanism.
1.2 Temperature- and humidity-sensitive bulk solids may need to be tested at different temperatures and moisture contents, as would happen in an industrial environment.
1.3 The maximum particle size should be limited to 3 mm, to reduce the likelihood of binding the slide gate.
1.4 This standard is not applicable to all bulk solids and segregation mechanisms: while sifting is a common segregation mechanism experienced by many bulk solids, other segregation mechanisms not evaluated by this standard might induce segregation in practice. Practice D6941 covers another common mechanism: fluidization.
1.5 The extent to which segregation will occur in an industrial situation is not only a function of the bulk solid and its tendency to segregate, but also the handling equipment (for example, bin design), process (for example, transfer rates), and environment.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D6940 − 10
Standard Practice for
1
Measuring Sifting Segregation Tendencies of Bulk Solids
This standard is issued under the fixed designation D6940; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* D2216 Test Methods for Laboratory Determination of Water
(Moisture) Content of Soil and Rock by Mass
1.1 This practice covers an apparatus and procedure for
D3740 Practice for Minimum Requirements for Agencies
simulating the segregation tendencies of bulk solids by means
Engaged in Testing and/or Inspection of Soil and Rock as
of the sifting mechanism.
Used in Engineering Design and Construction
1.2 Temperature- and humidity-sensitive bulk solids may
D6941 Practice for Measuring Fluidization SegregationTen-
need to be tested at different temperatures and moisture
dencies of Powders
contents, as would happen in an industrial environment.
1.3 The maximum particle size should be limited to 3 mm, 3. Terminology
to reduce the likelihood of binding the slide gate.
3.1 Definitions:
1.4 This standard is not applicable to all bulk solids and 3.1.1 Forcommondefinitionsoftermsinthisstandard,refer
to Terminology D653.
segregation mechanisms: while sifting is a common segrega-
tion mechanism experienced by many bulk solids, other 3.1.2 funnel flow pattern, n—a flow sequence in a bin or
hopper characterized by having some bulk solids moving
segregation mechanisms not evaluated by this standard might
through stagnant bulk solids. In general, there is no flow along
induce segregation in practice. Practice D6941 covers another
the hopper walls.
common mechanism: fluidization.
3.1.3 segregation, n—a process through which blended or
1.5 The extent to which segregation will occur in an
uniform powders or bulk solids become non-uniform, with
industrial situation is not only a function of the bulk solid and
regions of varying composition, for example, particle size.
its tendency to segregate, but also the handling equipment (for
example, bin design), process (for example, transfer rates), and
3.1.4 sifting segregation, n—a mechanism in which finer
environment.
particles preferentially percolate into a zone within the bulk
solid.
1.6 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.2 Definitions of Terms Specific to This Standard:
standard.
3.2.1 collection cup, n—a collection cup holds a specimen
of bulk solid once it is discharged from the apparatus.
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.2.2 inner hopper, n—the inner hopper is transparent. It has
responsibility of the user of this standard to establish appro-
a steep inner conical section designed to sit within the outer
priate safety and health practices and determine the applica-
hopper.
bility of regulatory limitations prior to use.
3.2.3 outer hopper, n—the outer hopper consists of a shal-
low transparent hopper designed to provide funnel flow for
2. Referenced Documents
most bulk solids. It has an attached slide gate/guide cylinder
2
2.1 ASTM Standards:
and support legs.
D653 Terminology Relating to Soil, Rock, and Contained
3.2.4 representative sample, n—a quantity of the bulk solid
Fluids
to be tested that is representative of that solid in an industrial
application being studied. Parameters of interest that may
1
This practice is under the jurisdiction of ASTM Committee D18 on Soil and
affect whether or not a sample is representative include, but are
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization
and Handling of Powders and Bulk Solids.
not limited to: moisture, particle size distribution, raw material
Current edition approved July 1, 2010. Published August 2010. Originally
variation, method of production, aging, chemical composition.
approved in 2003. Last previous edition approved in 2004 as D6940–04. DOI:
10.1520/D6940-10.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 4. Summary of Practice
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1 A representative sample of a bulk solid is placed in the
Standardsvolume information, refer to the standard’s Document Summary page on
the ASTM website. upper hopper of the apparatus.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6940 − 10
4.2 The bulk solid is discharged to form a pile wi
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This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D6940–04 Designation:D6940–10
Standard Practice for
1
Measuring Sifting Segregation Tendencies of Bulk Solids
This standard is issued under the fixed designation D6940; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This practice covers an apparatus and procedure for simulating the segregation tendencies of bulk solids by means of the
sifting mechanism.
1.2 Temperature- and humidity-sensitive bulk solids may need to be tested at different temperatures and moisture contents, as
would happen in an industrial environment.
1.3 The maximum particle size should be limited to 3 mm, to reduce the likelihood of binding the slide gate.
1.4 This standard is not applicable to all bulk solids and segregation mechanisms: while sifting is a common segregation
mechanism experienced by many bulk solids, other segregation mechanisms not evaluated by this standard might induce
segregation in practice. Practice D6941 covers another common mechanism: fluidization.
1.5 The extent to which segregation will occur in an industrial situation is not only a function of the bulk solid and its tendency
to segregate, but also the handling equipment (for example, bin design), process (for example, transfer rates), and environment.
1.6
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
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 Practice for Minimum Requirements forAgencies Engaged inTesting and/or Inspection
of Soil and Rock as Used in Engineering Design and Construction
D6941 Practice for Measuring Fluidization Segregation Tendencies of Powders
3. Terminology
3.1 Definitions—Definitions of terms used in this test method shall be in accordance with Terminology For common definitions
of terms in this standard, refer to Terminology D653.
3.1.1 funnel flow pattern, n—a flow sequence in a bin or hopper characterized by having some bulk solids moving through
stagnant bulk solids. In general, there is no flow along the hopper walls.
3.1.2 segregation, n—a process through which blended or uniform powders or bulk solids become non-uniform, with regions
of varying composition, for example, particle size.
3.1.3 sifting segregation, n—a mechanism in which finer particles preferentially percolate into a zone within the bulk solid.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 collection cup, n—a collection cup holds a samplespecimen of bulk solid once it is discharged from the apparatus.
3.2.2 inner hopper, n—the inner hopper is transparent. It has a steep inner conical section designed to sit within the outer
hopper.
3.2.3 outer hopper, n—the outer hopper consists of a shallow transparent hopper designed to provide funnel flow for most bulk
solids. It has an attached slide gate/guide cylinder and support legs.
1
This practice is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.24 on Characterization and
Handling of Powders and Bulk Solids.
Current edition approved Jan.July 1, 2004.2010. Published February 2004.August 2010. Originally approved in 2003. Last previous edition approved in 20032004 as
D6940–03.D6940–04. DOI: 10.1520/D6940-104.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standardsvolume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
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