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Powder particle testing standards are published by ASTM and ISO. These include the standard test method for measuring minimum fluidization velocities of free-flowing particles and determination of apparent density of washing powders by measuring the mass of a given volume. These calculations and tests are invaluable to those who work with power particles in applications where mass and density are key factors.

ASTM D7743-12

Standard Test Method for Measuring the Minimum Fluidization Velocities of Free Flowing Powders

1.1 This test method describes the apparatus and procedure needed for determining the minimum fluidization velocity of Geldart Group A powders and the minimum fluidization or complete fluidization velocity of Geldart Group B powders. 1.1.1 This test method is for powders that are readily or easily fluidizable and fall into the category of Group A and B of the ???Geldart??? classification. The fluidization of Geldart Group C powders will be addressed in another standard. This test method could apply to Geldart Group D particles but the focus of this document is towards Group and A and B materials. 1.1.2.1 Group A powders are easily fluidized but there is a difference between the gas velocity where the bed is initially fluidized and the velocity where bubbles are first observed. For Group A powders, bed expansion can be considerable before any bubbles are observed. Group B powders are also easily fluidized; but there is no difference between the velocity where the bed is fluidized and the velocity at the onset of bubbling. The minimum gas velocity, where all of the particles are fully supported by the gas for Group B powders, is often referred to as the ???complete fluidization velocity??? instead of minimum fluidization velocity. Group C powders are cohesive and can be difficult to fluidize. 1.1.2.2 Group A powders can be distinguished from Group B powders by the response to deaeration. Group A powders deaerate relatively slowly whereas Group B powders deaerate almost instantaneously in fluidized beds. 1.1.2.3 Group A Powders that lie near or on the Group A/C boundary may be tested by this method. However, if the powders do not fluidize freely, test results should be considered invalid. 1.1.2.4 Temperature, moisture (water) content, particle size distribution, particle shape and sometimes other variables influence the Geldart classification of a powder. Deaeration testing specified in 1.1.2.2 is a more definitive test than simply using particle size and density differences as described in 1.1.2 . Note 1 ??? A Standard Practice for deaeration testing is under development. 1.2 This test method should be performed in a laboratory under controlled conditions of temperature and humidity. 1.3 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026. 1.3.1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as the industry standard. In addition they are representative of the significant digits that generally should be retained. The procedures used do not consider material variations, the purpose for obtaining the data, special purpose studies, or any considerations for the user???s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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ISO 697:1981

Surface active agents -- Washing powders -- Determination of apparent density -- Method by measuring the mass of a given volume

The method consists in determining the mass of powder in receiver of known dimensions, after filling with the sample from a funnel of specified shape under specified conditions. The method is applicable to free flowing powders and, provided that an appropriate funnel is used, to powders which have a tendency to cake. In the case of powder containing lumps, the method is applicable only if these can be disintegrated readily without braeking down the particles of the powder.

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