SIEVING. In the final separation operation, restraint is imposed on some of the particles by mechanical screens that prevent their passage. This is done successively, using increasingly smaller screens, to give a series of particles classified into size ranges.
where F ' (D) is the derivative of F(D) with respect to D.
So dF = F '(D)dD
and so integrating between D1and D2 gives the cumulative fraction between two sizes D2 (larger) and D1 which is also that fraction passing through sieve of aperture D2 and caught on that of aperture D1.
Sieve size mm % retained
through 0.063 4
plot a cumulative sieve analysis and estimate the weight fraction of particles of sizes between 0.300 and 0.350 mm and 0.350 and 0.400 mm.
Less than aperture (mm)
63 125 250 500 1000
4 12 40 89 100
This has been plotted on Fig. 6.1. and the graph F(D) has been smoothed. From this the graph of F'(D) has been plotted, working from that slope of F(D), to give the particle size distribution.
FIG. 6.1. Particle-size analysis forms, perhaps the best being the