CAKING
Testing with the REVOLUTION
Powder Analyzer
Cohesive
particles in a powder can form larger particles with
material handling. This process can be intentional as in a
granulation process or can be unintentional as in caking
during storage. Either way a powder's quality is
affected by the formation of these larger particles.
The
REVOLUTION Caking Test
can be used to study powders that exhibit particle size
change during mixing, blending,
transportation, production processing and/or storage.
Caked
Powder
Powder after
De-Caking
When
a cohesive powder is stored, the powder's particles can join or stick together forming large particles.
The flow properties of this caked powder will change with the formation of larger particles.
This
caking process is studied by comparing a powder's flow
properties in a rotating drum before and after storage.Once your powder has caked, the REVOLUTION Caking Test can also test the strength of the
caked particles by increasing the drum rotation speed to force
high velocity collisions between the powder particles. These
collisions could cause the caked particles to
break up. The caking software compares the results
of the powder's properties after storage and after
the increase in velocity to see if the powder remained in
a caked state.
Appropriate powders
for the REVOLUTION Caking test include:
food
powders, cosmetics, pharmaceuticals, and other powders
with caking potential. The caking analysis should
be performed on any powder with caking tendencies where the existence of large particles should be
minimized.
The
REVOLUTION Granulation Test has five process steps:initial
analysis, caking, caking analysis, de-caking, and
de-caking analysis. These
steps are discussed below.
Initial Step
The initial step will indicate the powder's initial
product characteristics by measuring the statistical
analysis described below. These initial
parameters as seen in Figure A will be used
as a comparison to the caking and de-caking analysis steps. The software
measures
the powder's ability to granulate or cake during storage by
comparing the
initial granulation analysis to that of powder stored for a
specified amount of time.
Initial Process
CakingStep
The
agglomeration or caking step is performed in
process or in a special storage container (off of
the instrument) that
allows load to be applied to the powder. A powder sample is
taken after the caking process and the new sample is loaded into the test
drum.
Caking
Analysis
The caking analysis indicates if the powder
caked or clumped in the agglomeration step.
The analysis is completed by determining the percentage
of change in the statistical analysis between the
initial stage and the caking stage.
Caking
Analysis
In Figure A,
the analysis shows a increase in the
powder's avalanche power and time during the
caking stage. This change in
power and time indicates that cakes are
being formed during the caking step. The formulation of
cakes causes the powder to avalanche less frequently and flow
less freely. In most caking applications, the user wants to
know how much caking is occurring and how quickly the powder is
caking.
In
Figure A, the conclusion is
made that this powder is caking in the caking process step.
Figure
A- Cumulative Power Spectrum - -
Avalanche Time vs. Power -
Initial
Analysis (RED) Caking
Analysis (BLUE)
De-Caking Step
The
de-caking step can be performed within the REVOLUTION
Powder Analyzer or in the manufacturing process.
Within the instrument,
the powder is rotated at a high fixed velocity for
a set time to force particle
collisions. The rotation speed
and time of rotation of the de-caking
process are set based on the process parameters. In
the manufacturing process, a new powder sample is
taken after de-caking process or material
handling. The new
sample is loaded into the test drum.
De-Caking Process
De-Caking Analysis
The
de-caking analysis will indicate if the
clumps formed during the caking step break up with an increased
rotation speed.
This step is important for caking applications
because if the powder formed large particles during the
processing stage, it is important to know what
force is required to break up these particles before
packaging and storage. The
analysis is completed by determining the
percentage of change in the statistical parameters
from the caking analysis to the de-caking analysis.
De-Caking Analysis
In Figure B,
the analysis shows an decrease in the powder's
avalanche power and time. Based on this analysis,
the conclusion is made that the granules formed
during the caking process have broken up
into smaller particles with the increased rotation
speed in the de-caking stage.
Figure
B - Cumulative Power Spectrum -
Avalanche Time vs. Power - Caking
Analysis (BLUE) De-Caking
Analysis (GREEN)
In
Figure C, the analysis shows the
difference in the avalanche power and time
between the powder's initial analysis,
caking analysis and the de-caking analysis. In
addition, a comparison is made between the results
of the de-caking stage to the initial stage
to see if the powder returns to its initial
powder's characteristics. Therefore,
the conclusion is made that the powder did
in fact return to its initial powder
characteristics.
Figure
C - Cumulative Power Spectrum -
Avalanche Time vs. Power - Initial
Analysis (RED) Caking
Analysis (BLUE) De-Caking
Analysis (GREEN)
In Figure D, the graphical analysis shows
the volume the powder sample at the various stages
- initial, caking and de-caking. The volume
of the caked sample is
increasing during the process due to the rotating
causing the clumps to break up. After the
de-caking process, the sample volume is significantly
increased due to the reduction of caking and the
introduction of air molecules within powder
sample.
Figure
D - Sample Volume Analysis -
Time vs. Powder Volume -
Initial
Analysis (RED) Caking
Analysis (BLUE) De-Caking
Analysis (GREEN)
In
Figures E and F, the graphical
analysis shows two different powders:
one powder that exhibits caking behavior
and one power that does not.
Figure
E -
Cumulative Power Spectrum - Avalanche
Time vs. Power - Caking
Figure
F -
Cumulative Power Spectrum
- Avalanche
Time vs. Power - No Caking
Once
the granulation test has been completed, the
software will provide the user with the
following statistical analysis for all three
analysis steps: initial, agglomeration and
de-agglomeration.
Please doubleclick on any of the parameters for a
brief measurement description.