Sieves, nesting

Analytical sieving may also be done with the solids in a liquid suspension. In this case, it is called wet sieving, and the suspension is transferred to the nested sieves and rinsed through with solvent. The suspended particles are captured on the sieves in the same manner as described above. 

Figure 4.5 Diagram of a nested sieve set used for stream sediment sampling. Top cross-section plan view (dimensions in millimetre). Bottom cut-away 3-D visualisation [from engineering drawing by Humphrey Wallis, BGS for ABS (acetyl butyl styrene) polymer plastic sieve sets].

This system was developed in an attempt to eliminate some of the problems associated with nest sieving and to automate the process [110,111]. A hexagonal sieving chamber is supported on discs and rotated. A steady stream of powder is fed to the entry port and, as the sieve rotates, the powder gently moves across the surface. As the sieve rotates further, the powder is picked up by a vane and dumped out of the other side of the... 

A variation of this system is the installation of 0.5 in diameter sieves mounted on a spinning riffler to obtain small, representative powder samples, which can be sieved in situ without removing the miniature sieves from the riffler system [113]. By mounting several different aperture sieves around the riffler, a confederation of miniature sieves could replace nest sieving. 

Cellector tissue sieves (Bellco Glass Company) 2 nesting sieves, upper one with 40 mesh to remove large contaminants, lower one with 150 mesh or finer to retain embryos... 

The basic nest sieving procedure of the type used in the Ro-tap machine has been automated by the Rotex Company in a machine known as the Gradex 2000 Particle... 

Research projects have suggested that a multisectioned surface of a sieve can minimize the effects due to aperture distributions in the sieve. It has also been suggested that confederated miniature sieves may be able to replace nest sieving [39, 40]. 

B. H. Kaye, G. G. Clark, Confederated Miniature Sieves as an Alternative to Nest Sieving . Part. Char., 3 (1986) 145—150. 

The data for a plot like Fig. 18-60 are easily obtained from a screen analysis of the total crystal content of a known volume (e.g., a liter) of magma. The analysis is made with a closely spaced set of testing sieves, as discussed in Sec. 19, Table 19-6, the cumulative number of particles smaller than each sieve in the nest being plotted against the aperture dimension of that sieve. The fraction retained on each sieve is weighed, and the mass is converted to the equivalent number of particles by dividing by the calculated mass of a particle whose dimension is the arithmetic mean of the mesh sizes of the sieve on which it is retained and the sieve immediately above it. 

The sieving operation starts by mounting the sieves in a nest, the coarsest at the top. The sample is placed on the top screen, and the screens are shaken for several minutes. It is generally impossible to screen a sample completely the longer one shakes the screens, the more material comes thru, although to a continu-... 

The presence of methylenic bands shifted at higher frequency in the very early stages of the polymerization reaction has also been reported by Nishimura and Thomas [114]. A few years later, Spoto et al. [30,77] reported an ethylene polymerization study on a Cr/silicalite, the aluminum-free ZSM-5 molecular sieve. This system is characterized by localized nests of hydroxyls [26,27,115], which can act as grafting centers for chromium ions, thus showing a definite propensity for the formation of mononuclear chromium species. In these samples two types of chromium are present those located in the internal nests and those located on the external surface. Besides the doublet at 2920-2850 cm two additional broad bands at 2931 and 2860 cm are observed. Even in this favorable case no evidence of CH3 groups was obtained [30,77]. The first doublet is assigned to the CH2 stretching mode of the chains formed on the external surface of the zeolite. The bands at 2931 and... 

A wt retained ori designated sieve B = wt retained on sieves nested above designated sieve W wt of specimen... 

M) Granulation. Place a 100 g sample and a silver quarter (25 ) on a specified nest of sieves, properly superimposed and assembled with a bottom pan. Break up lumps or aggregates by gentle brushing with a camel s hair brush. Cover and shake for 3 mins by means of a mechanical shaker geared to produce 300 +15 gyrations and 150 + 10 taps... 

By shaking a lOOg sample thru a nest of appropriate US sieves and weighing the residue remaining on each sieve... 

Sampler 1 downstream of the water sampling will wash the trenching tool (shovel), sieve nest, both pans, the plastic funnel and both sets of thick black protective rubber gloves with stream water. The sieve nest (Fig. 4.5) is assembled on the top of the glass-fibre pan, in a stable position, as close to the sediment collection point as possible. The collection pan and sieves must be clean and free from any particulate matter before the commencement of sampling. 

Sieve analysis utilizes a series or stack, or nest of electro brass or... 

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