AS 4816.1–2002 pdf free download.Determination of particle size distribution by gravitational liquid sedimentation methods Part 1: General principles and guidelines.
Sedimentation techniques may be classified as either incremental or cumulative. Incremental methods are used to determine the solids concentration (or suspension density) of a thin layer at a known height and time. Cumulative methods are used to determine the rate at which solids settle from the suspension. In both methods, the powder may be introduced either as a thin layer on top of a column of liquid (the line-start technique), or uniformly dispersed at the start of the analysis (the homogeneous technique). The cumulative method is not part of this part of ISO 13317. The incremental homogeneous technique is more often used in gravitational sedimentation (Figure 1) and is described in this part of ISO 13317. The line-start technique is more applicable to centrifugal sedimentation and is part of ISO 1331 8-2.
4.2 Calculation of particle size
Stokes diameters are calculated according to equation (2).
4.3 Calculation of cumulative mass percentage
The cumulative mass percentage according to the particle concentration gradient in the gravitational pipette method and in the gravitational X-ray method shall be determined according to ISO 1331 7-2 and ISO 1331 7-3 respectively.
4.4 Effect of measurement zone height on resolution
Information on the effect of measurement zone height on resolution is given in annex A.
5.3 Particle shape
At a low Reynolds number, the orientation of non-spherical particles is random, so a single particle will have a low range of settling velocities. As the Reynolds number increases, particles tend to align to give maximum drag and thus will settle at the slowest of the range of velocities possible with random orientation, so a particular particle may have a low or high velocity depending on its orientation.
5.4 Particle porosity
It is recommended that the effective particle density be determined where possible, i.e. the particle density be determined in the suspending liquid, plus dispersant that will be used in the sizing measurement. This will compensate for the presence of any closed porosity and also for open porosity to the extent that the chosen liquid penetrates the open porosity. For particles that are non-porous and of known composition, a density value may be taken from a handbook or determined experimentally. Information on the effect of open pores on the terminal velocity of spherical particles is given in annex D.AS 4816.1 pdf download.