Granular material density analyzer
Automated tapped density and compaction kinetics measurements
The bulk density, the tapped (or tap) density and the Hausner ratio measurement is very popular for powder characterization because of both the simplicity and the rapidity of the measurement. Moreover, the density and the ability of a powder to increase its density are important parameters for storage, transportation, caking, etc. This simple test has three major drawbacks. First, the result of the measurement depends on the operator. Indeed, the filling method influences the initial powder volume. Secondly, the volume measurements by naked eyes induce strong errors on the results. Finally, with this simple method, we completely miss the compaction dynamics between the initial and the final measurements.
GranuPack instrument is an automated and improved tapped density measurement method based on recent fundamental research results. The behaviour of the powder submitted to successive taps is analysed with an automatized device. The Hausner ratio Hr, the initial density and the tapped density are measured precisely (0.4% of accuracy). Moreover, a dynamical parameter n1/2 and an extrapolation of the maximum density ρ(∞) are extracted from compaction curves.
The powder is placed in a metallic tube with a rigorous automated initialization process. Afterward, a light hollow cylinder is placed on the top of the powder bed to keep the powder/air interface flat during the compaction process. The tube containing the powder sample rose to a fixed height of ΔZ and performs free falls. The free fall height is generally fixed to ΔZ = 1mm or ΔZ = 3mm. The height h of the powder bed is measured automatically after each tap.
Measurement is simple, fast and intuitive.
The intuitive software calculates and reports physical data. The results obtained under various conditions can be compared. Accessibility is password protected. All data are automatically collected and stored for post processing. Easy data transfer and automatic report generation.
Closed system for safety requirements and perfect for the calculation of powder bulk density.
Size compatible with hood or confined enclosure.
Recorded standard operating procedures increase the repeatability of measurements.
Through the simplicity of its design, Granupack maximizes uptime. It is made out of modules, each of them can be swapped to avoid extensive diagnostics. It results in accuracy of powder bulk density measurement.
A cylindrical tube filled with powder is submitted to a mechanical tap constraint. A sensor measures the powder density curve and a software calculates the powder bulk density, the taped density, the Hausner index, the Carr index and a kinetic parameter.
Analyzed volumes can vary from 10 to 1000cm3 using tubes of different sizes and materials.
Granupack is an improvement of the classical tap density tester and has been nicknamed high-resolution density meter by users. Granupack measures automatically the evolution of the powder density as a function of the tap number to obtain a complete compaction curve. This curve represents the compressibility of the powder while submitted to external constrains. Bulk density, tapped density and Hausner ratio are extracted from this compaction curve.
In addition to these classical parameters, the whole compaction curve gives dynamical information related to powder flowability.
Therefore, in addition to density characterization, GranuPack is a powder flow tester working in the quasi-static regime.
The automation of the measurement associated with the use of a powder bed initialization protocol leads to highly precise and reproducible results. The influence of the operator is supressed. This level of precision and reproducibility is not accessible with the classical tapped density tester based on naked eyes powder volume measurements.
For example, with Granupack, the uncertainties on bulk density, tap density and Hausner ratio measurement is lower than 1% of the average result with stainless steel powders. This precision opens new perspective for considering our improved tapped density measurement method in emerging applications like additive manufacturing.
The range of powders and granular materials measurable with Granupack and giving relevant results is very wide from nanopowders to millimetric grains: nanotubes, active pharma ingredients, excipients, pigments, cement, sand, seeds, cattle feed, granules, tablets, pellets…