| Specification
Grading particles in the range 0.6 mm to 0.06 mm, a siltometer like the optical lever siltometer or the Puri;s siltometer is used . Where the bulk of material lies within this range, this method gives more accurate results than sieving.
The optical lever siltometer and Puri;s siltometer are based on the principal of settling rate of particles in column of liquid (usually water). The method of analysis by optical lever siltometer method is an incremental method. It determines Indirectly the rate of chain of concentration of the suspension at a known vertical distance below the upper surface of the suspension. Puri’s siltometer method is a cumulative method.
Puri`s Siltometer determines directly the rate of accumulation of the material by measuring the deposited sediment at the bottom of the tube. In the operation of this siltometer, assumptions are made that the particles to be measured are evenly distributed at the start of the experiment and have the same density. Furthermore, there is the implicit assumption that the fall velocity of each particle is independent of the others, a condition which is considered applicable if the concentration of the particles is not high (say up to 2%, although up to 5%such methods may be used). The particles of the different sizes fall through the column of water with different velocities. The size distributions of the particles varies all along the length of the suspension and the concentration decreases as the sedimentation continues..
For a point at a distance from the surface at a given time from the beginning of the sedimentation, some of the particles pass below this and approach the bottom. The sediments concentration and consequently, the density, the density of the liquid column above the point is reduced. Therefore, the pressure at the point decreases. Suitable relations may be derived to determine precisely the size distribution of the particles at any point at any time in terms of change of pressures at the point with time . |
