ASTM D6941-19

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.
SCOPE
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...

General Information

• Status: Published
• Publication Date: 30-Apr-2019
• 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

Relations

• Replaces: ASTM D6941-12 - Standard Practice for Measuring Fluidization Segregation Tendencies of Powders
• Effective Date: 01-May-2019
• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D6940-18 - Standard Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
• Effective Date: 01-Jun-2018
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012
• Refers: ASTM D3740-12 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2012
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D3740-11 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Sep-2011
• Refers: ASTM D6940-10 - Standard Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
• Effective Date: 01-Jul-2010
• Refers: ASTM D2216-10 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Jul-2010
• Refers: ASTM D3740-10 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2010
• Refers: ASTM D653-09 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jan-2009
• Refers: ASTM D653-08a - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Dec-2008

Overview

ASTM D6941-19: Standard Practice for Measuring Fluidization Segregation Tendencies of Powders establishes a practical approach to evaluate the segregation potential of powders caused by fluidization. Fluidization segregation is a common issue in industries handling fine powders, as variations in particle size or composition can lead to vertical segregation within containers, bins, or transport vessels. Identifying a powder’s tendency to segregate during fluidization helps manufacturers ensure consistent product quality and process reliability.

This standard covers the apparatus and procedures required to fluidize a powder sample, create multiple specimens from it, and analyze these specimens for variance in key properties. Results can be compared to those from powders with known histories or processes, providing essential information for powder handling and process design.

Key Topics

• Fluidization Segregation Mechanism: Understanding how fine and coarse particles separate due to air entrainment, especially during rapid bin filling, pneumatic conveyance, or high airflow conditions.
• Test Apparatus and Procedure:
  • Detailed requirements for the gas supply, test chamber with stacked cylinders, distributor, expansion chamber, and filters.
  • Specified procedures for fluidizing the powder, dividing the sample, and analysis.
• Parameters Analyzed: Focus on properties such as particle size distribution, chemical composition, bulk density, and color to determine degree of segregation.
• Sampling and Reporting:
  • Instructions for obtaining a representative powder sample and for reporting all relevant test and specimen data.
  • Emphasis on laboratory practices to ensure reliable, repeatable results.
• Applicability and Limitations: Not suitable for all bulk solids or all segregation mechanisms. Restricted to powders that can be fluidized; does not evaluate segregation by sifting (see ASTM D6940 for that mechanism).
• Environmental Conditions: Takes into account temperature- and moisture-sensitive powders, recommending testing conditions that replicate industrial scenarios.

Applications

ASTM D6941-19 is used across a range of industries where powder blending, handling, storage, or transport are critical to product quality and process efficiency. Practical applications include:

• Quality Assurance in Powder Manufacturing: Evaluate new or existing powders for risk of segregation during handling, reducing variability in final products.
• Process and Equipment Design: Select appropriate bin designs, filling rates, and conveying systems based on measured segregation tendencies.
• Comparative Studies: Compare candidate powders or suppliers to select materials less prone to segregation, optimizing consistency in downstream operations.
• Research and Development: Support formulation changes or process improvements with quantitative segregation tendency data.
• Industrial Troubleshooting: Identify causes of product non-uniformity in bulk solids handling systems by testing powders under conditions simulating real plant environments.

Related Standards

ASTM D6941-19 references and complements several other ASTM standards:

• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D2216: Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• ASTM D3740: Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• ASTM D6940: Practice for Measuring Sifting Segregation Tendencies of Bulk Solids (addresses segregation by sifting rather than fluidization)

Utilizing ASTM D6941-19 helps ensure powder handling and processing systems are robust, minimizing quality issues related to fluidization segregation, and supporting compliance with international best practices in bulk solids management.

Keywords: fluidization segregation, powder segregation, test method, bulk solids, ASTM D6941-19, powder handling, quality assurance, particle size distribution

Standards Content (Sample)

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.
Designation: D6941 − 19
Standard Practice for
Measuring Fluidization Segregation Tendencies of Powders
This standard is issued under the fixed designation D6941; 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* the adequacy of a given professional service must be judged,
nor should this document be applied without consideration of
1.1 This practice covers an apparatus and procedure for
a project’s many unique aspects.The word Standard in the title
creating several specimens of a powder sample that, if the
of this document means only that the document has been
powder is one that segregates by the fluidization mechanism,
approved through the ASTM consensus process.
should be different from one another.
1.9 This standard does not purport to address all of the
1.2 A powder sample is fluidized then, after the fluidizing
safety concerns, if any, associated with its use. It is the
gas is turned off, it is separated into three or more specimens
responsibility of the user of this standard to establish appro-
that can be analyzed for parameters of interest. The difference
priate safety, health, and environmental practices and deter-
in these parameters between the specimens is an indication of
mine the applicability of regulatory limitations prior to use.
the segregation potential of the powder.
1.10 This international standard was developed in accor-
1.3 Powders must be capable of being fluidized in order to
dance with internationally recognized principles on standard-
be tested by this practice.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.4 Temperature- and moisture-sensitive powders may need
mendations issued by the World Trade Organization Technical
to be tested at different temperatures and moisture contents, as
Barriers to Trade (TBT) Committee.
would happen in an industrial environment.
1.5 This standard is not applicable to all bulk solids and
2. Referenced Documents
segregation mechanisms: while fluidization is a common
2.1 ASTM Standards:
segregation mechanism experienced by many fine powders,
D653 Terminology Relating to Soil, Rock, and Contained
other segregation mechanisms not evaluated by this standard
Fluids
might induce segregation in practice. Practice D6940 covers
D2216 Test Methods for Laboratory Determination of Water
another common mechanism: sifting.
(Moisture) Content of Soil and Rock by Mass
1.6 The extent to which segregation will occur in an
D3740 Practice for Minimum Requirements for Agencies
industrial situation is not only a function of the powder and its
Engaged in Testing and/or Inspection of Soil and Rock as
tendency to segregate, but also the handling equipment (for
Used in Engineering Design and Construction
example, bin design), process (for example, transfer rates), and
D6940 Practice for Measuring Sifting Segregation Tenden-
environment.
cies of Bulk Solids
1.7 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 For common definitions of technical terms in this
1.8 This practice offers a set of instructions for performing
standard, refer to Terminology D653.
one or more specific operations. This document cannot replace
educationorexperienceandshouldbeusedinconjunctionwith
4. Summary of Practice
professional judgment. Not all aspects of this practice may be
4.1 Arepresentative sample of a powder is placed in the test
applicable in all circumstances. This ASTM standard is not
chamber.
intended to represent or replace the standard of care by which
4.2 Pressurized gas (usually air), which is blown from the
bottom, is ramped up from zero to a pre-determined High
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2019. Published May 2019. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2003. Last previous edition approved in 2012 as D6941–12. DOI: Standardsvolume information, refer to the standard’s Document Summary page on
10.1520/D6941-19. 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
D6941 − 19
criteria of Practice D3740 are generally considered capable of competent
Flow-rate, held there, ramped down to a pre-determined Low
and objective testing/sampling/inspection/etc. Users of this practice are
Flow-rate, then held there, all for specified times, creating a
cautioned that compliance with Practice D3740 does not in itself assure
state of fluidization of the powder.
reliable results. Reliable results depend on many factors; Practice D3740
provides a means of evaluating some of those factors.
4.3 The airflow is ramped down to zero over a specified
Practice D3740 was developed for agencies engaged in the testing
time.
and/or inspection of soil and rock. As such it is not totally applicable to
4.4 The powder in the test chamber is divided into N agencies performing this practice. However, users of this practice should
recognize that the framework of Practice D3740 is appropriate for
specimens.
evaluating the quality of an agency performing this practice. Currently
4.5 The specimens are then available to be tested for
there is no known qualifying national authority that inspects agencies that
differences relevant to the application, for example, particle perform this practice.
size or chemical assay.
6. Apparatus
5. Significance and Use
6.1 The apparatus is shown in Fig. 1. It consists of the
5.1 Fluidization segregation can cause vertical segregation
following:
within bins used to hold and transport powders. This can affect
6.2 Gas Supply with Flow Meter—A supply of dry, non-
product quality or subsequent processes in industrial applica-
toxic and non-flammable gas capable of fluidizing the powder
tions.
is required. The recommended gas supply pressure is 170 kPa
5.2 By measuring a powder’s segregation tendency, one can
[25psig]witharangefrom100to200kPa[15to30psig].The
compare results to other powders with known history, or
recommended gas supply flow rate is 10 000 cm /min or
determine if the given powder may have a tendency to
higher.The gas flow rate shall be adjustable during the test.An
segregate in a given process.
automated controller may be used for this purpose.
NOTE 2—Generally, clean, dry air is used. If air is not suitable (that is,
5.3 Fine powders generally have a lower permeability than
it reacts with or adversely affects the powder being tested) another gas,
coarse bulk solids and therefore tend to retain air longer. Thus,
such as nitrogen, may be used.
when a bin is filled with a fluidizable powder, the coarser
6.3 Test Chamber—This consists of three or more cylinders
particles settle or are driven into the bed while the finer
stacked above the distributor, which is at the top of the air
particles remain fluidized near the surface.
supply plenum. These cylinders which, when stacked together
5.4 Fluidization, which serves as a driving force for this
have a total height of at least 195 mm, are connected at the top
mechanism of segregation, is likely to occur when fine pow-
to a conical expansion chamber. The test chamber is where the
ders are pneumatically conveyed into a bin, the bin is filled or
powder sample is placed.
discharged at high rates, or if sufficient air flow counter to the
6.3.1 Cylinders—Each circular cylinder is transparent and
flow of powder is present within the bin.
has a diameter of 24 6 1 mm I.D. They are stacked, identified
NOTE 1—The quality of the result produced by this practice is
as #1 (the bottom) to #N (the top). The bottom cylinder (#1)
dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that meet the sits against the distributor in the air supply plenum. The top
FIG. 1 Apparatus
D6941 − 19
FIG. 2 Timing Profile
cylinder (#N) mates to the expansion chamber. The cylinders appropriate, its moisture (water) content using Test Method
shall be held together in a manner that prevents separation D2216 or another method specified by the requesting agency.
during the test and prevents leakage. This method must allow
7.5 Carefully spoon or scoop the powder into the test
separation of the cylinders upon completion of the test to allow
chamber. Fill it to a height of 170 6 5 mm.
specimen recovery.
7.6 Attach the expansion chamber and filter.
6.4 Expansion Chamber—This conical extension of the test
chamber allows the powder to disengage from the air stream. It
7.7 IftherequestingagencyhasnotspecifiedvaluesofHigh
must be sufficiently tall to prevent the expanded powder bed
Flow-rate and Low Flow-rate for the powder to be tested, an
from contacting the filter at its top and sufficiently steep to
initial test of the powder is required prior to running this test;
cause the powder to slide back into the test chamber when the
See Annex A1, “Determining Inputs.”
airflow is turned off.
7.8 Start the airflow using the
...

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: D6941 − 12 D6941 − 19
Standard Practice for
Measuring Fluidization Segregation Tendencies of Powders
This standard is issued under the fixed designation D6941; 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 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 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.
1.9 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.10 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.
2. Referenced Documents
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
D6940 Practice for Measuring Sifting Segregation Tendencies of Bulk Solids
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 Nov. 1, 2012May 1, 2019. Published December 2012May 2019. Originally approved in 2003. Last previous edition approved in 20052012 as
ε1
D6941–05–12. . DOI: 10.1520/D6941-12.10.1520/D6941-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
D6941 − 19
3. Terminology
3.1 Definitions:
3.1.1 For common definitions of technical terms in this standard, refer to Terminology D653.
3.1.2 fluidization, n—in powders, the state in which a powder exhibits fluid-like properties.
3.1.3 fluidization segregation, n—in powders, a mechanism that causes vertical segregation, that is, horizontal layering of fine
and coarse particles, as resulting from fluidization of the bulk solid.
3.1.4 segregation, n—in powders, 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 Definitions:
3.1.1 For common definitions of technical terms in this standard, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 high flow-rate, n—in powders, the first stage flow-rate used to initiate fluidization.
3.2.2 low flow-rate, n—in powders, the second stage flow-rate used to maintain fluidization.
3.2.3 representative sample, n—in powders, a quantity of the bulk solid to be tested that is representative of that solid in an
industrial application being studied. Parameters of interest that may affect whether or not a sample is representative include, but
are not limited to: moisture, particle size distribution, raw material variation, method of production, aging, chemical composition.
4. Summary of Practice
4.1 A representative sample of a powder is placed in the test chamber.
4.2 Pressurized gas (usually air), which is blown from the bottom, is ramped up from zero to a pre-determined High Flow-rate,
held there, ramped down to a pre-determined Low Flow-rate, then held there, all for specified times, creating a state of fluidization
of the powder.
4.3 The airflow is ramped down to zero over a specified time.
4.4 The powder in the test chamber is divided into N specimens.
4.5 The specimens are then available to be tested for differences relevant to the application, for example, particle size or
chemical assay.
5. 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.
6. Apparatus
6.1 The apparatus is shown in Fig. 1. It consists of the following:
6.2 Gas Supply with Flow Meter—A supply of dry, non-toxic and non-flammable gas capable of fluidizing the powder is
required. The recommended gas supply pressure is 170 kPa [25 psig] with a range from 100 to 200 kPa [15 to 30 psig]. The
recommended gas supply flow rate is 10 000 cm /min or higher. The gas flow rate shall be adjustable during the test. An automated
controller may be used for this purpose.
NOTE 2—Generally, clean, dry air is used. If air is not suitable (that is, it reacts with or adversely affects the powder being tested) another gas, such
as nitrogen, may be used.
D6941 − 19
FIG. 1 Apparatus
FIG. 2 Timing Profile
6.3 Test Chamber—This consists of three or more cylinders stacked above the distributor, which is at the top of the air supply
plenum. These cylinders which, when stacked together have a total height of at least 195 mm, are connected at the top to a conical
expansion chamber. The test chamber is where the powder sample is placed.
6.3.1 Cylinders—Each circular cylinder is transparent and has a diameter of 24 6 1 mm I.D. They are stacked, identified as #1
(the bottom) to #N (the top). The bottom cylinder (#1) sits against the distributor in the air supply plenum. The top cylinder (#N)
mates to the expansion chamber. The cylinders shall be held together in a manner that prevents separation during the test and
prevents leakage. This method must allow separation of the cylinders upon completion of the test to allow specimen recovery.
6.4 Expansion Chamber—This conical extension of the test chamber allows the powder to disengage from the air stream. It must
be sufficiently tall to prevent the expanded powder bed from contacting the filter at its top and sufficiently steep to cause the powder
to slide back into the test chamber when the airflow is turned off.
6.5 Filter—The filter prevents powder from being blown out of the apparatus while allowing the gas to pass through. The filter
material should be appropriate for the applicatio
...