The POWDER FLOW ANALYSER (PFA/PL) is an accurate and reliable method of measuring the flow characteristics of powders. It can be rapidly fitted to a Stable Micro Systems plus series Texture Analyser, enabling manufacturers to assess and avoid typical problems such as batch and source variation of ingredients, caking during storage/transportation and problems with discharging from hoppers or bins.
The Powder Flow Analyser is supplied with library tests so operators can start testing quickly and conveniently after straightforward installation and calibration. Users can, however, fully program the instrument to carry out slicing, shearing, compressing, compacting and aerating cycles in any combination.
Samples
are placed in a standard (140ml) or small (25ml) borosilicate glass
vessel; allowing users to observe the powder as the sample is displaced.
The powder is conditioned at the beginning of each test to eliminate
any variations in loading and the precision-engineered, patented blade
is then rotated through the sample, causing “controlled flow”. Stable Micro Systems use the test frame and vertical drive system provided by a universal Texture Analyser, and add the additional rotational drive and software functionality to form the Powder Flow Analyser – an accurate and reliable method of measuring the flow characteristics of powders.
The Powder Flow Analyser may be purchased as a completely new working system, or you can take your existing plus Texture Analyser and attach the Powder Flow Analyser to extend your range of testing solutions from powders to end products.
A patented helically machined rotor can be programmed to move through a powder column in different ways depending upon the characteristic that is to be measured. Due to the unique precision profile of the rotor’s blade, the sample can be physically displaced in many different ways. The Test Settings of blade path angle and tip speed determine the mode of Controlled Flow achieved within a sample column.
A typical tests starts with conditioning the powder column to remove operator loading differences. Depending upon the programmed rotation of the blade in terms of path angle, blade direction and tip speed, the powder column can be displaced in a number of different ways to suit the process and properties to be measured.
During the test, axial force, time and distance are measured by a sensitive transducer and data is displayed and analysed in real time by Exponent software. Sample results can be ranked and compared to assess the impact of external conditions including humidity and moisture content, surface properties, electrostatic charge and particle or granule size, shape and distribution.
Once programmed, the optimised test can provide identical controlled flow conditions when completing the same test programme. 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.
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| Comparison of Cake Breaking Test results for 1 day consolidation vs 4 days consolidation |
The Powder Caking and Consolidation Rig (PFA/PCC), designed for location on a Powder Flow Analyser, allows the assessment of the sample’s caking behaviour after consolidation.
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 cakes may lead to issues with discharge of powders from storage hoppers or silos and may also impact on customer perception of products – as it could appear that the product is less voluminous than stated.
The sample is prepared by filling a static consolidation tube to a chosen volume or weight. A 2kg compactor is introduced into the tube and allowed to rest on the powder column under controlled environmental conditions for a given period of time after which the sample is tested using a special PFA blade. The area under the curve in the mid-section of the graph is taken as the work to break the cake. The greater this value, the stronger the cake.
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| Assessment of powder compaction |
The Powder Compaction Rig is available in two variants. The High Tolerance Powder Compaction Rig (A/PCR) is suited to high force applications where the punch/die clearance is critical. As such this fixture is auto-aligned using a universal adapter. The Low Tolerance Powder Compaction Rig (A/PCRS) is suited to other powder compaction applications such as assessing granule friability, where the punch/die clearance is less critical.
Compaction properties of powders can be assessed using target force or target distance modes. Many powder compacts are formed to a target distance and so the Powder Compaction Rigs can be used to assess required force. New advances in tabletting machines allow compression to a target force resulting in powder compacts with constant porosity. The Powder Compaction Rig can be used with target force mode to assess the effect of fill level/weight on tablet thickness.
Papers that investigate powder properties using a TA.XTplus Texture Analyser have been published, some examples of which are listed below:
ALSENZ, J., DU CASTEL, P. & CIRELLI, G. (2007). Miniaturized Intrinsic Dissolution Screening (MINDISS) assay for early formulation. Poster presented at: AAPS, San Diego, 2007.
EDUARDO, M. de F. & da SILVA LANNES, S. C. (2006). Use of texture analysis to determine compaction force of powders. Journal of Food Engineering, 80 (2), 568-572.
FRENNING, G., ALDERBORN, G., KISH, L. B. & MAHLIN, D. (2008). Spectral analysis of force fluctuations during probe penetration into cohesive powders. Powder Technology, 187 (1), 62-67.
GHOSAL, S., INDIRA, T. N. & BHATTACHARYA, S. (2010). Agglomeration of a model food powder: Effect of maltodextrin and gum arabic dispersions on flow behaviour and compacted mass. Journal of Food Engineering, 96 (2), 222-228.
HAGSTEN, A., LARSEN, C. C., SONNERGAARD, J. M., RANTANEN, R. & HOVGAARD, L. (2008). Identifying sources of batch to batch variation in processability. Powder Technology, 183 (2), 213-219.
KAERGER, J. S., EDGE, S. & PRICE, R. (2004). Influence of particle size and shape on flowability and compactability of binary mixtures of paracetamol and microcrystalline cellulose. European Journal of Pharmaceutical Sciences, 22, 173-179.
NADA, A. H., AL-SAIDAN, A. M. & MUELLER, B. W. (2005). Improving the physical and chemical properties of ibuprofen. Pharmaceutical Technology (www.pharmtech.com), November.
SCHULE, S., SCHULZ-FADEMRECHT, T., GARIDEL, P., BECHTOLD-PETERS, K. & FRIEß, W. (2008). Stabilization of IgG1 in spray-dried powders for inhalation. European Journal of Pharmaceutics and Biopharmaceutics, 69 (3), 793-807.
SORENSEN, A. H., MOLLER-SONNERGAARD, J., HOVGAARD, L., LARSEN, C. C., JEPSEN, S. K. & LINDNER, H. (2005). Characterization of powders by low-pressure compression test. Pharmaceutical Development and Technology, 10 (2), 197-209.
We can design and manufacture probes or fixtures for the TA.XTplus texture analyser that are bespoke to your sample and its specific measurement.
Once your measurement is performed, our expertise in its graphical interpretation is unparalleled. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can also prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.
For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.
The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is
available to measure and analyse the textural properties of a huge range of
food products. Our technical experts
can also custom design instrument fixtures according to individual
specifications.No-one understands texture analysis like we do!
To discuss your specific test requirements click here...
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