Sieve aperture

Sieve no. Nominal aperture Sieve no. Nominal aperture Sieve no. Nominal aperture Sieve no. Nominal aperture ... 

Rocks. Rock samples are reduced to 1—2 mm fragments by a jaw crusher or percussion mortar. They are then reduced to a fine powder to pass a 200 mesh (63 pm aperture) sieve by means of a swing-mill such as the one produced by Tema Machinery Ltd., Banbury, Oxon, U.K. Agate mortars for this device are expensive but do not contaminate the sample with trace metals. A hard steel mortar is suitable if contamination with traces of chromium can be tolerated. Small hammer mills are suitable for the fine grinding, but as... 

Heywood measured crushed sandstone which had passed through a 11/8 in. square aperture sieve and been retained on a 1 in. square aperture... 

The tolerances with micromesh sieves are much better than those for woven-wire sieves the apertures being guaranteed to 2 pm of nominal size apertures except for the smaller aperture sieves. Each type of sieve has advantages and disadvantages [38] e.g. sieves having a large percentage open area are structurally weaker but measurement time is reduced. 

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. 

Sand is defined by the American Society for Testing and Materials (ASTM) as granular rock particles that pass through a No. 4-mesh (4.75-mm aperture) U.S. standard sieve, are retained on a No. 200-mesh (75- i.m aperture) sieve, and result from the natural disintegration or comminution of rock. Sands are also produced by physical beneficiation of rocks by crushing. These sands have various chemical compositions, determined by the type of rock being mined. 

Preparation of test solution. Polypropylene (3 g) is extracted under reflux with 50.0 ml of chloroform using a hotplate or a heating mantle. If quantitative analysis by HPLC, UV spectroscopy or colorimetry is required, then the sample should be ground, preferably with liquid nitrogen, and the fraction passing a 14 mesh (1.18 mm aperture) sieve extracted for 1 h. If only granular material is available then 3 h extraction will be adequate for identification purposes. For film samples 3 h extraction will be adequate for quantitative results. 

Species separated by molecular sieving effects when kinetic diameters fall iato different zeoHte aperture size categories (standard molecular sieve diameters = 300, 400, 500, 800, 1000,1300 pm. 

The particle mass retained by each sieve is determined by weighing after drying when necessary, and each fraction is designated by the sieve size it passed and the size on which it was retained. The sieve diameter of a particle is therefore defined as the size of the sieve aperture through which the particle in question just passes through. Mass fractions of the particles are then presented in tabular or graphical form. 

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. 

Sieving Methods and Classification Sieving is probably the most frequently used and abused method of analysis because the equipment, an ytical procedure, and basic concepts are deceptively simple. In sieving, the particles are presented to equal-size apertures that constitute a series of go-no-go gauges. Sieve analysis presents three major difficulties (1) with woven-wire sieves, the weaving process produces three-dimensional apertures with considerable tolerances, particularly for fine-woven mesh (2) the mesh is easily damaged in use (3) the particles must be efficiently presented to the sieve apertures. 

Sieves are often referred to by their mesh size, which is the number of wires per hnear unit. The U.S. Standard Sieve Series as described by the American Society of Testing and Materials (ASTM) document E-11-87 Standard Specification for Wire-cloth Sieves for Testing Purposes addresses sieve opening sizes from 20 [Lm (635 mesh) to 125 mm (5.00 in). Electroformed sieves with square or round apertures and tolerances of 2 [Lm, are also available. 

The mesh number is the number of apertures per unit length of sieve. 

Figure 1.12 Sieve mesh L, aperture size W, wire width...

The particle size of powder most often used for consolidation is —200 mesh (74 /xm sieve aperture), and the most widely practised method of consolidation is hot pressing in vacuo. 

Sieving is probably the easiest and certainly the most popular method of size analysis but is restricted to powders having the greater1 portion coarser than 75 y, For finer powders the method is limited by the high cost of producing sieves with uniform, small apertures... 

The classical approach for particle size determination, or more correctly for particle size selection - which is still used for solids like soils, sediments and other technical materials like coal, and also for biological materials - is sieving analysis. The raw material is milled, generally after drying, see Section 2.1, and if the required particle size is obtained, typically ranging from <0.1 to a few mm, it is allowed to pass sieves with different apertures to discard coarse particles and remaining materials. For materials consisting of numerous different particles microscopical inspection is used. 

Sieve analysis, based on either vibratory or suction principle, uses a series of standard sieves calibrated by the National Bureau of Standards. The method is generally used for screening coarse particles down to a material as fine as 44 pm (No. 325 sieve). Sieves produced by photoetching and electroforming techniques are now available with apertures from 90 down to 5 pm. 

Dsi is the sieving diameter, equal to the width of the minimum aperture through which the particle will pass. 

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