Standard Test Method for Measuring the Permeability of Powders as a Function of Consolidation Using the Freeman Technology FT4 Powder Rheometer

Importancia y uso:

5.1 The test method can be used to evaluate the following:

5.1.1 Classification or Comparison of Powders—Both the measured PD_q and calculated gas permeability can be used to classify powders relative to each other.

5.1.2 Sensitivity Analysis—The test can be used to evaluate the relative effects of a range of powder properties or environmental parameters, or both, such as (but not limited to) humidity, particle size and size distribution, particle shape and shape distribution, moisture content and temperature.

5.1.3 Quality Control—The test can be used to assess the PD_q and gas permeability of a feedstock, intermediate or product against pre-determined acceptance criteria.

5.1.4 Process Design and Operation—The determined parameters can be used to quantify powder behavior in numerous processing environments. The ability of a powder to discharge consistently from a storage vessel, through pipes or down chutes is primarily dependent on its flow properties, interaction with the material of construction and the geometry of the equipment (1 and 2)3. However, design methodologies assume that there is a gas interchange between the top and bottom of the stored powder that allows consistent flow through the outlet. Gas permeability is a controlling factor in discharge rates (1 and 2). Powders with low gas permeability may exhibit reduced or intermittent/pulsatile flow, or both, that cannot be predicted from only considering shear and dynamic flow properties. This could lead to poor filling or discharge of cavities/bags/vessels and thus result in poor weight uniformity or slow discharge. Furthermore, a powder with low gas permeability may be more likely to have compromised compression properties in tableting operations due to increased entrained gas after the filling stage and a reduced ability to release this gas during compression.

Note 1: The quality of the result produced by this test method is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this test method are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors. Additional guidance on sampling of powders is given in Reference (3).

Practice D3740 was developed for agencies engaged in the testing and/or inspection of soil and rock. As such it is not totally applicable to agencies performing this test method. However, users of this test method should recognize that the framework of Practice D3740 is appropriate for evaluating the quality of an agency performing this practice. Currently there is no known qualifying national authority that inspects agencies that perform this test method.

Subcomité:

D18.24

Volúmen:

04.09

Número ICS:

13.080.20 (Physical properties of soils)

Palabras clave:

Freeman Technology; FT4 Powder Rheometer; normal stress; gas permeability; powder; powder bed; pressure drop; superficial gas velocity;