AMETEK Brookfield Page 30
Manual No. M09-1200-F1016
IV.3.1 The Flow Function Test
The Standard Flow Function Test employs 5 Consolidation Stresses using Geometric Spacing between
each stress, 3 over consolidation stresses at each consolidation stress, and one special consolidation
stress for the test at the tangent to the Unconfined Mohr Circle. (See the Help file in the software for
additional detail on this last statement.)
The Standard Flow Function Test runs 35 test conditions on one sample, to explore fully the complex
behavious of a powder. This gives the highest level of confidence in the relevance of results when
comparing different powders. It is in line with long-established protocols. Brookfield recommends
the Standard Flow Function Test as the best test to use when obtaining powder flow data for comparing
powder behaviour, for Quality Control purpose, for equipment design/assessment or any other
purposes, provided you can spare the time to run it (around 34 minutes).
The Quick Flow Function Tests (5-point and 2-point) have been developed to give faster tests (18
minutes and 14 minutes respectively) for users who cannot spare the time to run the Standard Flow
Function Test and are happy with a less sensitive comparison between powders. They measure fewer
test conditions (total of 6 for the 2-point and 15 for the 5-point test) so the results do not capture
the full behaviour of the powder. Where the powders are more than about 10% different from one
another in flowability, these short tests will give useful indicative comparisons, but for powders that
are fairly close in behaviour, the differences may not be apparent.
Do not attempt to compare Flow Functions obtained from different tests (E.g. 2-point against standard,
or 5-point against 2-point) because the comparison is likely to be incomplete.
The Quick Flow Function Tests are excellent for doing a first-stage screening if you have a large
number of powders and you wish to quickly bracket them into groups by flow properties (say to
find the ones that are most likely troublesome and deserve more detailed measurements). Even
the 2-point test will reliably indicate where there are substantial differences in behaviour between
powders. Some users find they can use the 5-point test for Quality Control purposes, to identify
batches within a single production stream that could be troublesome. However, if you wish to use
the “quick” tests for QC, Brookfield recommends a investigation in which you run the Standard,
5-point and 2-point tests in parallel on a substantial number of production samples to ensure that
the quick test does indeed identify any differences that you consider significant. Once you have
satisfied yourself that this is the case, then always use the same test (Standard Flow Function, 5- or
2-point Quick Flow Function) for that QC procedure. Do not be tempted to compare data between
the three test types. As a general rule, the smaller the differences you are looking to discriminate,
then the larger the number of test points you will require.
Once the test has been selected, click on the “Display Test Stresses” button to view the number of
steps in your program as shown in Figure IV-5. In this case a standard flow function test has been
selected. The two columns on the right show the sequence for the consolidation stresses and the
corresponding overconsolidation stresses that will be applied. Note that the time estimate for the test
to run is displayed in the window at the top right of the Main Screen. Units are hours:minutes:seconds.
