Sieve Construction

Sieves are typically constructed in one of two ways: first, through the use of a wire mesh or cloth. This

Table 1 Sieve mesh equivalent sizes: US standard testing sieves designated for wire cloth at some principal ISO sizes

Mesh number:

Sieve opening

US standard testing sieves

(mm)

5

4.00

7

2.80

10

2.00

14

1.40

18

1.00

25

0.710

36

0.500

45

0.355

60

0.250

80

0.180

120

0.125

190

0.090

325

0.045

results in square apertures. The diameter of the wire controls the size of the aperture and per cent of the total area that is open. Second, openings or circular holes are created by perforating a plate or flat disc. The number of perforations controls the amount of open area in this sieve. These two methods result in openings that differ in shape and in their ability to pass particles. Thus, it is important to specify which kind has been used to obtain a particular set of data.

Sieves are available in standard sizes (Table 1) from a number of companies. Sieve openings are given in a mesh number or nominal diameter of the opening. Surprisingly, no standard sieve is readily available for the 50 |im cut-off between the sand and silt separates (as defined in some systems of particle nomenclature). Consequently, sieving cannot distinguish this class boundary directly using standard sieves. However, such boundaries (or other specific sizes) can be estimated by determining the particle size distribution with a nest of sieves that bracket the desired size.

Industry standards have focused on maintaining consistency in the manufacture of sieves. This allows the comparison of sieving operations provided the materials and conditions of the sieving are also comparable. The focus of many practitioners of sieving has been on standard procedures to maintain repro-ducibility and consistency.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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