Sizing

Introduction:

What is the concept of Mesh and Sieve? And how the US Sieve and Tyler Mesh size equivalent?

These are all discussed under with respect to the particle size distribution......

Mesh means any of the open spaces in a net. Mesh material are used in finding out the particle size distribution of granular material. Let us say for example, Pea nuts placed on a mesh with 5mm openings and when the mesh is shaking, small broken pieces and dust pass through the mesh while whole pea nuts are retained in the Mesh. A Commercial pea nut buyer might use a test like this to determine a Batch of pea nuts has too many broken pieces. This type of test is common in some industries to make uniform test methods, and in this way several standardized mesh series have been established. In this regard one well- known mesh series came into picture i.e., Tyler Equivalent Mesh size. Sieve is the device in which unwanted material can be separated from wanted material, and sieving is a technique of separating materials of different size fractions. They can arrange in stacks to divide samples up into various size fractions and hence determine Particle size distribution. Sieves and screens are usually used for longer particle sized materials i.e., greater than approximately 50 microns, and micron itself is a measure of one millionth of a meter or one twenty five thousandth of an inch.

Mesh size?

Mesh size is the number openings per linear inch.

One notation for indicating particle size distribution using mesh size is to use + and – designations.

A “+ “ before the mesh indicates, particles are retained by the screen.

A “– “ before the mesh indicates, particles are passed into the screen.

Typically 90% or more of the particles will lie within the indicated range.

For example, if the particle size of a material described as -4 +40 mesh, then 90% or more material will pass through a 4 mesh sieve (particles smaller than 4.76mm) and be retained by 40 mesh sieve (particles larger than 0.420mm).To calculate the size of the openings in a mesh the thickness of the wires make up the mesh material be taken into account. As the number describing the mesh size increases, the size of the particles decreases. Higher numbers equal finer material. Mesh size is not a precise measurement of particle size. But the supplier of our screens does not offer any screens finer than 500 mesh. If you think about it, the finer the weave, the closer the wires get together, eventually leaving no space between them at all. So, beyond 325-400 mesh, we usually describe particle size in “microns”.


Test sieve:






Sizing - Mineral Process Engineering

Linear Equivalent:
One micron= 0.0000394 inches.
25,400 microns= 1 inch.
1000 microns= 1 mm.

MESH TO MICRONS COVERSION TABLE

U.S. MESH INCHES MICRONS MILLIMETERS
3 0.2650 6730 6.730
4 0.1870 4760 4.760
5 0.1570 4000 4.000
6 0.1320 3360 3.360
7 0.1110 2830 2.830
8 0.0937 2380 2.380
10 0.0787 2000 2.000
12 0.0661 1680 1.680
14 0.0555 1410 1.410
16 0.0469 1190 1.190
18 0.0394 1000 1.000
20 0.0331 841 0.841
25 0.0280 707 0.707
30 0.0232 595 0.595
35 0.0197 500 0.500
40 0.0165 400 0.400
45 0.0138 354 0.354
50 0.0117 297 0.297
60 0.0098 250 0.250
70 0.0083 210 0.210
80 0.0070 177 0.177
100 0.0059 149 0.149
120 0.0049 125 0.125
140 0.0041 105 0.105
170 0.0035 88 0.088
200 0.0029 74 0.074
230 0.0024 63 0.063
270 0.0021 53 0.053
325 0.0017 44 0.044
400 0.0015 37 0.037


QUESTIONS AND ANSWERS:

(1). What is Mesh number?
Ans: Mesh number is the no of openings per linear inch.

(2). If the particle size of a material described as -12 +45, then what does it mean?
Ans: It means that 90% or more material will pass through a 12 mesh sieve (particles smaller than 1.680mm) and retained by 45 mesh sieve(larger than0.354 mm).

(3). Beyond which mesh range the particles described as microns?
Ans: Beyond 325-400 mesh.

(4). What is Micron?
Ans: A micron is a unit of length equivalent to a millionth of a meter. 1 micron = 1 μm = 10-6 m.

(5). 200 Mesh sieve particle size represents?
Ans:74 microns,0.074mm openings.

References:

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