Particle size analysis by sieving
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Particle size analysis by sieving


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Organization for Standardization, Geneva are: ISO 3310-1 for wire cloth 
[19], ISO 3310-2 for perforated plate [20], and ISO 3310-3 for 
electroformed [21]. 
212 Powder sampling and particle size determination 
As well as these, several industries have their own specifications; 
aggregates [22], porcelain [23], ceramic powders [24], plastics [25], 
coating powders [26], concrete [27] and metals [28]. The standard for 
glass spheres [29] is designed specifically for sieve analysis of glass 
spheres used in reflective road and pavement markings and other industrial 
uses. 
ISO 2395 [30] and ASTM E1638-94 [31] describe the terminology used 
in sieve analysis. 
Most test sieves are certified and manufactured to ISO 9002 standards. 
Table 4.1 Nominal apertures and permissible variations for a selection 
of US woven wire sieves 
Standard 
(mm) 
\ nsxi 
63.0 
31.5 
16.0 
8.0 
4.0 
2.0 
1.0 
(l-^ m) 
850 
300 
150 
125 
106 
90 
75 
38 
20 
Alternative 
(in) 
5 
2.500 
1.250 
0.625 
0.312 
0.157 
0.0787 
0.0394 
(in) 
0.0331 
0.0117 
0.0059 
0.0049 
0.0041 
0.0035 
0.0029 
0.0015 
0.0008 
Tolerance 
(±mm) 
3 J 
1.9 
1.0 
0.5 
0.25 
0.13 
0.070 
0.040 
(t^m) 
35 
14 
8 
7 
6 
5 
5 
3 
3 
Intermediate 
(mm) 
i3o!o 
65.6 
32.9 
16.7 
8.41 
4.23 
2.135 
1.080 
(^tm) 
925 
337 
174 
147 
126 
108 
91 
48 
29 
Maximum 
(mm) 
66.2 
33.2 
17.0 
8.58 
4.35 
2.215 
0.135 
im) 1 
970 
363 
192 
163 
141 
122 
103 
57 
35 
4.3 Tolerances for standard sieves 
The apertures for the British Standard 400 mesh are 37.5 |iim with a 
nominal wire thickness of 26 )Lim. On the basis of Table 4.1, in which a 
selection of sieve dimensions are shown, the (nominal) 75 \xm sieve has a 
Sieving 213 
median aperture size in the range 70-80 |um and not more than 5% of the 
apertures shall fall in the (intermediate to maximum) size range of 91-103 
|Lim. This implies that there is a probability of having a 103 |im aperture in 
a nominal 75 jum sieve. {The percentage of undersize apertures is not 
relevant since only particles smaller than the nominal aperture size can 
pass through them. Their sole (detrimental) contribution is to reduce the 
effective open area of the sieve and thus increase sieving time}. The 
relative tolerance increases with decreasing nominal size leading to poor 
reproducibility when analyses are carried out using different nests of 
(uncalibrated) sieves. Electroformed sieves with square or round apertures 
and tolerances of ±2 |j,m are also available. 
Woven wire sieves, having apertures ranging from 20 [im to 125 mm, 
are readily available in 100, 200, 300 and 450 mm diameters frames as 
well as 3, 8, 12 and 18 in diameters. Microplate sieves are available in 100 
and 200 mm diameters with round or square apertures ranging from 1 to 
125 mm. Endecottes' test sieves have at least five intermediate and one 
final inspection in which wire cloth dimensions are inspected by projector. 
4.4 Woven-wire and punched plate sieves 
Sieve cloth is woven from wire and the cloth is soldered and clamped to 
the bottom of cylindrical containers [10,13]. Although the apertures are 
described as square, they deviate from this shape due to the three-
dimensional structure of the weave. In the weaving process, the weft wires 
are 'crimped' on to the warp wires for added strength; vigorous cleaning, 
for example with a wire brush, can separate the wires leading to oversize 
apertures. Fine sieves are usually woven with phosphor bronze wire, 
medium with brass, and coarse with mild steel. 
Heavy-duty sieves are often made of perforated plate giving rise to 
circular holes [12]. Various other shapes, such as slots for sieving fibers, 
are also available. Special purpose sieves are available in stainless steel 
and the flour industry uses nylon or silk. 
Bates discusses screen mesh fabric selection and how the material 
should be fixed to the frame, particularly with regard to stretching the 
material and adjusting the tension [32]. 
Wahl [33] describes the production of highly wear resistant sieves in 
soft annealed plates of chromium steel by punching, plasma cutting or 
mechanical working followed by heating and strain hardening. 
A method of preparing a metal sieve cloth holder has been described in 
which parallel grooves were cut on a metal mandrel [34]. These were 
214 Powder sampling and particle size determination 
filled with an insulating material to produce a network of conducting and 
non-conducting lines. After passivating the mandrel, copper wire was 
wound perpendicular to the linear net to give the pattern, and the whole 
immersed in a nickel plating bath. Two thousand five hundred holes per 
cm^ were produced with a nickel deposition of 25 to 30 |Lim. 
The cylindrical sieve cloth containers (sieves) are formed in such a way 
that they will stack, one on top of the other, to give a snug fit (Figure 4.3). 
Due to the method of manufacture, woven wire sieves have poor 
tolerances, particularly as the aperture size decreases. Tolerances are 
improved and the lower size limit extended with electroformed micromesh 
sieves. 
qc: IP 
Fig. 4.3 Stacking of sieves. 
4.5 Electroformed micromesh sieves 
Micromesh sieves [11] were first described by Daescher et. al [35] and are 
available in standard sizes ranging from 500 jum down to 3 jum. Etched 
sieves usually have round or square apertures, ranging in size from 500 to 
1200 |Lim, but other aperture shapes are available. They are available in 3, 
8 and 12 in diameter frames, as well as custom-made sizes. Other aperture 
sizes are also available and Zwicker reports using a 1 \xm sieve [36]. 
Sieving 215 
216 Powder sampling and particle size determination 
The photo-etching process is as follows. A fully degreased metal sheet is 
covered on both sides with a photosensitive coating and the desired pattern 
is applied photographically to both sides of the sheet. Subsequently the 
sheet is passed through an etching machine and the unexposed metal is 
etched away. Finally, the photosensitive coating is removed. A supporting 
grid is made by printing a coarse line pattern on both sides of a sheet of 
copper foil coated with photosensitive enamel. The foil is developed and 
the material between the lines etched away. The mesh is drawn tautly over 
the grid and nickel-plated on to it. The precision of the method gives a 
tolerance of ±2 jum for apertures from 300 to 500 |Lim reducing to ±1 jum 
for apertures from 5 to 106 |Lim. Some typical sieve meshes are illustrated 
in figure 4.4. 
For square mesh electroformed sieves, the pattern is ruled on to a wax-
coated glass plate with up to 8000 lines per inch, with each line 0.0001 in 
wide, and the grooves are etched and filled. The lower aperture size limit 
for off-the-shelf sieves is about 5 |Lim but apertures down to 1 |Lim have 
been produced. The percentage open area decreases with decreasing 
aperture size, ranging from 31.5% for 40 |Lim aperture sieves, to 2.4% for 5 
|Lim aperture sieves; this leads to greatly extended sieving time when using 
the smaller aperture sieves. These were originally available only in 3 in 
diameter frames but this has been extended to 8 in and 12 in frames. 
Buckbee Mears also make 10 and 20 cm diameter frames with apertures 
down to 3 jam. 
Sieves are available with a greater open area; this reduces the sieving 
time but the sieves are more fragile. Burt [37] examined samples of the 
finer sieve cloth and found that the average width of metal between 
openings for each grade of cloth was one-third to one-half that 
recommended in ASTM El61-70. Veco manufacture round and square 
aperture sieves. The apertures for the former are in the shape of truncated 
cones with the small circle uppermost. This reduces blinding but also 
reduces the open area and therefore prolongs the sieving time. Where 
thicker sieves are required, the Veco sieves are subjected to further 
electrodeposition on both sides to produce biconical apertures. 
The tolerances with