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ASTM D6941-03

(Practice)

Standard Practice for Measuring Fluidization Segregation Tendencies of Powders

Standard Practice for Measuring Fluidization Segregation Tendencies of Powders

SCOPE
1.1 This practice covers an apparatus and procedure for simulating the segregation tendencies of powders by means of the fluidization mechanism.
1.2 Powders must be capable of being fluidized in order to be tested by this practice.
1.3 Temperature- and humidity-sensitive powders may need to be tested at different temperatures and moisture contents, as would happen in an industrial environment. Further, the gas supply (type, temperature, and humidity) should also match the industrial conditions.
1.4 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.
1.5 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.
1.6 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.

General Information

Status
Historical
Publication Date
09-Jul-2003
ICS
19.120 - Particle size analysis. Sieving
Technical Committee
D18 - Soil and Rock
Drafting Committee
D18.24 - Characterization and Handling of Powders and Bulk Solids
Current Stage
Ref Project

Relations

Replaced By
ASTM D6941-04 - Standard Practice for Measuring Fluidization Segregation Tendencies of Powders
Effective Date
01-Jan-2004
Referred By
ASTM D653-22 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
Effective Date
10-Jul-2003
Referred By
ASTM D6940/D6940M-20 - Standard Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
Effective Date
10-Jul-2003

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ASTM D6941-03 - Standard Practice for Measuring Fluidization Segregation Tendencies of PowdersASTM D6941-03 - Standard Practice for Measuring Fluidization Segregation Tendencies of Powders
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ASTM D6941-03 - Standard Practice for Measuring Fluidization Segregation Tendencies of Powders
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D 6941 – 03
Standard Practice for
Measuring Fluidization Segregation Tendencies of Powders
This standard is issued under the fixed designation D 6941; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 fluidization segregation, n—a mechanism that causes
vertical segregation, that is, horizontal layering of fine and
1.1 This practice covers an apparatus and procedure for
coarse particles, as resulting from fluidization of the bulk solid.
simulating the segregation tendencies of powders by means of
3.1.3 segregation, n—a process through which blended or
the fluidization mechanism.
uniform powders or bulk solids become non-uniform, with
1.2 Powders must be capable of being fluidized in order to
regions of varying composition, for example, particle size.
be tested by this practice.
3.2 Definitions of Terms Specific to This Standard:
1.3 Temperature- and humidity-sensitive powders may need
3.2.1 high flow-rate, n—the first stage flow-rate used to
to be tested at different temperatures and moisture contents, as
initiate fluidization.
would happen in an industrial environment. Further, the gas
3.2.2 hold time, n—the time for which the Low Flow-rate is
supply (type, temperature, and humidity) should also match the
held.
industrial conditions.
3.2.3 low flow-rate, n—the second stage flow-rate used to
1.4 This standard is not applicable to all bulk solids and
maintain fluidization.
segregation mechanisms: while fluidization is a common
3.2.4 ramp time, n—the time during which the airflow is
segregation mechanism experienced by many fine powders,
reduced from the Low Flow-rate to zero.
other segregation mechanisms not evaluated by this standard
3.2.5 representative sample, n—a quantity of the bulk solid
might induce segregation in practice.
to be tested that is representative of that solid in an industrial
1.5 The extent to which segregation will occur in an
application being studied. Parameters of interest that may
industrial situation is not only a function of the powder and its
affect whether or not a sample is representative include:
tendency to segregate, but also the handling equipment (for
moisture, particle size distribution, raw material variation,
example, bin design), process (for example, transfer rates), and
method of production, aging, chemical composition.
environment.
1.6 This standard does not purport to address all of the
4. Summary of Practice
safety concerns, if any, associated with its use. It is the
4.1 A representative sample of a powder is placed in the
responsibility of the user of this standard to establish appro-
apparatus.
priate safety and health practices and determine the applica-
4.2 Pressurized gas (usually air) is blown from the bottom at
bility of regulatory limitations prior to use.
a series of flow-rates for specified times, creating a state of
2. Referenced Documents fluidization of the powder.
4.3 Once the airflow is stopped, the powder in the test
2.1 ASTM Standards:
chamber is divided into three samples from the bottom, center,
D 653 Terminology Relating to Soil, Rock, and Contained
and top of the column.
Fluids
4.4 The samples are then available to be tested for differ-
3. Terminology
ences relevant to the application, for example, particle size or
chemical assay.
3.1 Definitions—Definitions of terms used in this test
method shall be in accordance with Terminology D 653.
5. Significance and Use
3.1.1 fluidization, n—the state in which a powder exhibits
5.1 Fluidization segregation can cause vertical segregation
fluid-like properties.
within bins used to hold and transport powders. This can affect
final product quality in industrial applications.
This practice is under the jurisdiction of ASTM Committee D18 on Soil and
5.2 By measuring a powder’s segregation tendency, one can
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization
compare results to other powders with known history, or
and Handling of Powders and Bulk Solids.
determine if the given powder may have a tendency to
Current edition approved July 10, 2003. Published August 2003.
Annual Book of ASTM Standards, Vol 04.08. segregate in a given process.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6941–03
5.3 Fine powders generally have a lower permeability than cylinders. The bottom cylinder sits against the diffuser in the
coarse bulk solids and therefore tend to retain air longer. Thus, air supply plenum. The top cylinder mates to the expansion
when a bin is being filled with a fluidizable powder, the coarser chamber. When the cylinders are stacked together, they make
particles settle or are driven into the bed while the finer up the test chamber, where the powder is placed. The as-
particles remain fluidized near the surface. sembled test chamber dimensions are 24 mm I.D. by at least
5.4 Fluidization, which serves as a driving force for this 185 mm tall. The test chamber should have at least 25 mm
mechanism of segregation, is likely to occur when fine pow- additional height to allow expansion of the powder bed. The
ders are pneumatically conveyed into a bin, the bin is filled or cylinders must be held together so they do not separate during
discharged at high rates, or if sufficient air flow counter to the the tests and so leakage does not occur, while still able to be
flow of powder is present within the bin. separated at the end of the test in a way to allow for sample
recovery. This can be done a number of ways, including taping
6. Apparatus
the sections together.
6.1 The apparatus including critical dimensions is shown in
6.4 Expansion Chamber—The expansion chamber allows
Fig. 1. It consists of the following:
the powder to disengage from the air stream.
6.2 Gas Supply with Flow Meter—A gas supply capable of
6.5 Filter—The filter prevents powder from being blown
fluidizing the powder is required (15 to 30 psig [100 to 200
out of the apparatus. The filter material should be appropriate
kPa] range, 25 psig [170 kPa] recommended, maximum flow
for the application and should not contaminate the powder
rate 10 000 cm /min). The gas flow rate must be adjustable
(which may affect the analysis of the samples), and should
during the test-an automated controller may be used for this
provide sufficient containment of the powder (from both a
purpose.
safety perspective and a loss of powder perspective).
6.6 Diffuser—The diffuser distributes the air uniformly into
NOTE 1—Generally, clean, dry air is used. If air is not suitable (that is,
the test chamber; therefore, a sufficient pressure drop across the
it reacts with or adversely affects the powder being tested) another gas,
such as nitrogen, may be used. diffuser is required.
6.3 Cylinders—Three transparent cylinders are stacked,
NOTE 2—A sintered metal disk, such as 5 μm filtration grade porous
stainless steel sheet available from Mott Industrial, Farmington CT, may
identified (from the bottom) as the bottom, center, and top
FIG. 1 Apparatus
D6941–03
FIG. 2 Timing Profile
be an appropriate material for the diffuser. Some cohesive powders do not
7.13 Allow additional time after stopping the airflow for the
fluidize well, and simply form an air channel through the test bed,
powder to settle completely.
allowing the air to flow past stationary powder. In this case additional
NOTE 5—Settlement is considered complete when the top powder
airflow will not serve to fluidize the powder. If this occurs, this test is not
surface no longer appears to move (typically several minutes for fine
valid. However, a diffuser with a lower pe
...

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1.1 This test method covers an apparatus and procedures for measuring properties of bulk solids, henceforth referred to as Carr Indices.2  
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Standard Practice for Measuring Sifting Segregation Tendencies of Bulk Solids

SIGNIFICANCE AND USE
5.1 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 or subsequent processes in industrial applications.  
5.2 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.  
5.3 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:  
5.3.1 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.  
5.3.2 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.  
5.3.3 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.  
5.3.4 Interparticle Motion—This can be caused during formation of a pile, by vibration, or by a velocity gradient across the flowing material.  
5.4 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.
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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 [1/8 in.], 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.  
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SIGNIFICANCE AND USE
5.1 The data from this test can be used to estimate the bulk density of materials in bins and hoppers and for material handling applications such as feeders.  
5.2 The test results can be greatly affected by the sample selected for testing. For meaningful results it is necessary to select a representative sample of the particulate solid with respect to moisture (water) content, particle-size distribution and temperature. For the tests an appropriate size sample should be available, and fresh material should be used for each individual test specimen.  
5.3 Initial bulk density, (ρb)initial, may or may not be used as the minimum bulk density. This will depend on the material being tested. For example, the two are often close to the same for coarse (most particles larger than about 6 mm), free-flowing bulk solids, but not for fine, aeratable powders.  
5.4 Bulk density values may be dependent upon the magnitude of the applied mass increments. Traditionally, the applied mass is doubled for each increment resulting in an applied mass increment ratio of 1. Smaller than standard increment ratios may be desirable for materials that are highly sensitive to the applied mass increment ratio. An example of the latter is a material whose bulk density increases 10% or more with each increase in applied mass.  
5.5 Bulk density values may be dependent upon the duration of each applied mass. Traditionally, the duration is the same for each increment and equal to 15 s. For some materials, the rate of compression is such that complete compression (no change in volume with time at a given applied compressive stress) will require significantly more than 15 s.
Note 1: The quality of the result produced by this standard is dependent on the competence of 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 ...
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1.1 This test method covers an apparatus and procedure for determining a range of bulk densities of powders and other bulk solids as a function of compressive stress.  
1.2 This test method should be performed in the laboratory under controlled conditions of temperature and humidity.  
1.3 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.  
1.3.1 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives, and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.  
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measure are included in this standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ASTM
ASTM D6941-19(Practice)
Standard Practice for Measuring Fluidization Segregation Tendencies of Powders

SIGNIFICANCE AND USE
5.1 Fluidization segregation can cause vertical segregation within bins used to hold and transport powders. This can affect product quality or subsequent processes in industrial applications.  
5.2 By measuring a powder's segregation tendency, one can compare results to other powders with known history, or determine if the given powder may have a tendency to segregate in a given process.  
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.
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 reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
Practice D3740 was developed for agencies engaged in the testing and/or inspection of soil and rock. As such it is not totally applicable to agencies performing this practice. However, users of this practice should recognize that the framework of Practice D3740 is appropriate for evaluating the quality of an agency performing this practice. Currently there is no known qualifying national authority that inspects agencies that perform this practice.
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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.  
1.3 Powders must be capable of being fluidized in order to be tested by this practice.  
1.4 Temperature- and moisture-sensitive powders may need to be tested at different temperatures and moisture contents, as would happen in an industrial environment.  
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.  
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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 consid...

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ASTM
ASTM D1140-17(Test Method)
Standard Test Methods for Determining the Amount of Material Finer than 75-μm (No. 200) Sieve in Soils by Washing

SIGNIFICANCE AND USE
5.1 Material finer than the 75-μm (No. 200) sieve can be separated from larger particles or soil aggregations can be broken down much more efficiently and completely by wet sieving than with dry sieving. Therefore, when accurate determinations of material finer than a 75-μm (No. 200) sieve are desired, these test methods are used on the test specimen prior to dry sieving, or as a determination of the percent of material that is finer than a 75-μm (No. 200) sieve. Usually the additional amount of material finer than a 75-μm (No. 200) sieve obtained in the dry sieving process is a small amount. If it is large, the efficiency of the washing operation should be checked, as it could be an indication of degradation of the soil (see Note 2).  
5.2 Method A shall be used with non-cohesive soils containing fine material with little or no plasticity. The specimen is soaked in water to facilitate the separation of the fine and coarse fractions prior to washing through the 75-μm (No. 200) sieve.  
5.3 Method B shall be used with soils, particularly clayey soils, where the fine material demonstrates plastic behavior and tends to adhere to the larger particles. To provide adequate fine grain dispersal, it is necessary to soak the specimen in a dispersing solution prior to washing through the 75-μm (No. 200) sieve.  
5.4 To facilitate determination of which method to utilize, the sample may be classified as non-cohesive or having plastic characteristics based upon procedures outlined in Practice D2488 or other means of determining the soil properties.
Note 1: The quality of the result produced by this standard 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 standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable ...
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1.1 These test methods cover the determination of the amount of material finer than a 75-μm (No. 200) sieve by washing of material with a maximum particle size of 75 mm (3 in.).  
1.2 The methods used in this standard rely on the use of water or a dispersant to separate and remove materials finer than a 75-μm (No. 200) sieve. During these processes soluble substances, such as salts and other minerals, may also be removed. It is not within the scope of this standard to differentiate between the removal of fine particles and soluble substances. It is recommended that materials containing significant amounts of soluble substances be tested using other methods of separation.  
1.3 Two methods for determining the amount of material finer than the 75-μm (No. 200) sieve are provided. The method to be used shall be specified by the requesting authority. If no method is specified, the choice should be based upon the guidance given in 5.2, 5.3, and 5.4.  
1.3.1 Method A—Test specimen is dispersed by soaking in water prior to wash sieving.  
1.3.2 Method B—Test specimen is dispersed by soaking in a dispersing solution prior to wash sieving.  
1.4 Units—The values stated in SI units are to be regarded as standard. Except the sieve designations are typically identified using the “alternative” system in accordance with Specification E11, such as 3 inch and No. 200, instead of the “standard” of 75-mm and 75-μm, respectively. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method. The use of balances or scales recording pounds of mass (lbm) shall not be regarded as nonconformance with this standard.  
1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026, unless superseded by this test method.  
1.5.1 The procedures used to specify how data are collected/recorded and calculated in this standa...

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ASTM
ASTM D7891-24(Test Method)
Standard Test Method for Shear Testing of Powders Using the Freeman Technology FT4 Powder Rheometer Shear Cell

SIGNIFICANCE AND USE
5.1 The test can be used to evaluate the following:  
5.1.1 Classification or Comparison of Powders—There are several parameters that can be used to classify powders relative to each other, the most useful being the measured shear stresses, cohesion, flow function and angle of internal friction.  
5.1.2 Sensitivity Analysis—The shear cell can be used to evaluate the relative effects of a range of powder properties or environmental parameters, or both, such as (but not limited to) humidity, particle size and size distribution, particle shape and shape distribution, water content and temperature.  
5.2 Quality Control—The test can, in some circumstances, be used to assess the flow properties of a raw material, intermediate or product against pre-determined acceptance criteria.  
5.3 Storage Vessel Design—Mathematical models exist for the determination of storage vessel design parameters which are based on the flow properties of powders as generated by shear cell testing, requiring shear testing at a range of consolidating stresses as well as the measurement of the wall friction angle with respect to the material of construction of the storage vessel. The methods are detailed in Refs. (1-3).3
Note 1: The quality of the result produced by this test method 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 test method are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors (4).
Practice D3740 was developed for agencies engaged in the testing and/or inspection of soil and rock. As such it is not totally applicable to agencies performing this test method. However, users of this test method shoul...
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1.1 This method covers the apparatus and procedures for quantifying the incipient failure properties of a powder as a function of the normal stress for a given level of consolidation. The method also allows the further determination of the unconfined yield strength, internal friction angles, cohesion, flow function, major principal stress and wall friction angle (with the appropriate wall coupon fitted to the correct accessory).  
1.2 These parameters are most commonly used to assist with the design of storage hoppers and bins using industry standard calculations and procedures. They can also provide relative classification or comparison of the flow behavior of different powders or different batches of the same powder if similar stress and shear regimes are encountered within the processing equipment.  
1.3 The apparatus is appropriate for measuring the properties of powders with a maximum particle size of 1 mm. It is practicable to test powders that have a small proportion of particles of 1 mm or greater, but it is recommended they represent no more than 5 % of the total mass in samples with a normal (Gaussian) size distribution.  
1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.  
1.4.1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.  
1.5 Un...

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