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Test Types


A VAST RANGE OF POWDERS - A WIDE RANGE OF PARAMETERS TO MEASURE...

Range of powders


Conditioning Cycles video
View Video Clip showing the
effect of Conditioning Cycles.

SAMPLE CONDITIONING

To remove any user loading variation and to normalise the powder column after filling and prior to testing, test protocols include a conditioning process. Data is not captured during this process but this ensures that each sample starts after the same influence and hence provides outstanding reproducibility.


Paint cohesion
Cohesion - when your products stick together and stand up for themselves.

Cohesion test results
Typical Cohesion graph.

COHESION

Assessment of Cohesion 

Cohesiveness is the tendency for particles of powder to cling together and agglomerate (form larger clusters of particles). The PFA measures this cohesion characteristic by moving the blade in such a way as to lift the powder.  A more cohesive powder will cling to itself and to the blade therefore reducing the force exerted on the base of the vessel. This is shown in the plotted data by a large negative force. 

How the Cohesion Test works - Summary

The powder blade moves down through the powder column using a "cutting" action to minimise compaction. The upward part of the cycle then lifts the powder and the force of the powder on the vessel base is recorded.

Measured Parameters

  • Cohesion Coefficient

  • Cohesion Index

Application of Data

The cohesion index is a useful quality control measure as changes in powder specification (formulation, particle size distribution, particle shape etc.), storage conditions and test environment can all influence the tendency of a powder to agglomerate. A change in the cohesive properties of a powder may have an important affect on production processes such as die filling that could impair production efficiency and product quality.

This quick analysis allows repeatable quantification of the cohesiveness of a bulk solid. Test results can be used to compare the sample being tested with previously analysed product, to assess if it is more cohesive or more free flowing.


Powder compact
Caking - when you need it...

Paprika
Caking - when you don't want it...

Cake Height Ratio
A look at the Cake Height 
Ratio will indicate caking 
potential and speed of 
compaction of a powder.

Eyeshadow test
Penetration test on eyeshadow
using a Texture Analyser.

CAKING

Assessment of Caking

Caking is the tendency of a powder to form large agglomerates during storage and transportation. The tendency of a powder to cake is closely related to its cohesiveness and generally a powder that is cohesive will also form a cake during the caking test. The strength of the cake will depend on a number of factors such as packing efficiency, particle to particle interactions and moisture content i.e. humidity. Understanding the caking properties of a powder are important as most powders will be stored in hoppers or silos, or transported at some point in the production process. A powder that cakes easily and forms a strong cake may not discharge easily from a silo when required. However the caking process can be intentional and a desired result such as in a granulation process or when required to form a 'cake'.

How the Caking Test works - Summary

The blade levels the top of the powder column and measures its height.  The blade then moves down through the column and compacts the powder to a pre-defined force (usually 750g). When it reaches this force it measures the height of the cake and slices up through the powder. This compaction cycle is repeated four more times. The 5th time the target force is reached the blade slices through the compacted cake of powder formed at the bottom of the vessel.

Measured Parameters

  • Column and cake height ratios

  • Cake Strength Work
  • Mean cake strength force

Caking strength can be a highly desirable property of a finished product and can be assessed easily using the Texture Analyser.

Application of Data

The tendency of a powder to cake can give important data about the properties of the powder after storage and transportation. The formation of strong, high height cakes may lead to issues with discharge of powders from storage hoppers or silos. Product settlement and cake formation may also impact on customer perception of products, as it may appear that the product is less voluminous than stated. Proper understanding of the caking characteristics of powder may assist manufacturers in minimising issues after storage or transportation.


Powder scoop
Powder Speed Flow Dependence - when decreasing/increasing sample throughput creates a problem.

PFSD graph
Typical PFSD graph.

POWDER FLOW SPEED DEPENDENCE

Assessment of Powder Flow Speed Dependence

Powder flow properties may change with increasing or decreasing flow speeds. For example a powder may become more resistant to flow as it is forced to flow faster or indeed it may become more free flowing as the flow speed increases. This issue can lead to under/filling, for example, as a result of process changes to meet increase output demand. The PFA measures this characteristic by assessing the work needed to move the blade though the powder at increasing speeds. An evaluation of the flow stability of the powder is also made by comparing the work needed to move the blade though the powder at the start of the test compared to the work required to move the powder at the same speed at the end of the test.

How the PFSD Test works - Summary

The powder flow speed dependency (PFSD) test provides 5 sets of 2 cycles at increasing speeds. The downward parts of the cycles compact the powder and the upward stroke of the cycle uses a lifting action. 

The test measures resistance of a powder sample as controlled flow is imposed at different speeds. Powders that flow freely will transfer very little resistance through the powder column in either a downward or an upward direction. Conversely, poorly flowing powders exhibit substantial amounts of force in either direction.

Measured Parameters

  • Compaction Coefficients at each speed

  • Cohesion Coefficient
  • Flow Stability

Application of the Data

PFSD gives important information about the speed flow properties of a powder and this can be of interest in a production environment.  It may be necessary to convey a powder through plant at a certain speed to meet production volume requirements. The PFSD test can assess the suitability of a powder for different conveying speeds or test a powder for variations in speed flow properties from batch to batch. PFSD can also give important data on the attrition characteristics of the powder.


Fingerprint

COLLATE YOUR RESULTS

Once your range of tests are performed, the collection of parameters you have obtained can be collated into a 'fingerprint' of each sample.

Results bar charts


Optimum Flow Performance
Optimum Flow Performance.

CREATE YOUR OWN TEST

Controlled Flow technology enables the sample to be physically displaced in many different ways. The Test Settings of blade path angle and blade tip speed determine the mode of Controlled Flow achieved within a sample column. Once programmed, the Test Settings can be exactly repeated test after test.

The Test Settings can be optimised to show the maximum differentiation between similar products, or to imitate the process or storage handling conditions, experienced by the product.

Precision manufactured Rotor Blades (optimised patent applied design), and test vessels ensure that Powder Flow Analysers always provide identical controlled flow conditions when completing the same test programme.

Nothing surprises us more than what experienced users want to investigate. That is why for Research & Development needs we allow the flexibility for you to not only customise the test projects that we provide but also for you to completely create your own test protocols to test in a different way or analyse your data to collect additional parameters.

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