Particle size or mesh number

 

What is the particle size or mesh number of a granular medium?

Each sieve has a number that indicates how many crossing wires there are in one linear inch. A number 8 sieve has 8 vertical wires and 8 horizontal wires per inch. This creates an 8 × 8 grid of openings within each square inch. For example, a number 8 sieve has eight openings per inch in each direction.

Screening separates a mix of particles into fractions of different sizes. Larger particles are retained on a sieve, while smaller particles pass through and continue until another sieve holds them.

Sieves are used in stacks to obtain several fractions and determine the particle size distribution. They are suitable for particles larger than about 50 microns (0.050 mm).

Each mesh has a number that indicates how many cross threads there are in one linear inch. A mesh number 8 has 8 vertical threads and 8 horizontal threads per inch. This forms a grid of 8 × 8 spaces within each square inch. For example, a number 8 mesh has eight spaces per inch in each direction.

In water-treatment media, particle size is expressed with two numbers. For example, an 8 × 30 activated carbon contains particles that pass through the number 8 sieve and are retained on the number 30 sieve. This range corresponds to particles between 2.38 mm and 0.595 mm.

Example of laboratory sieves from the U.S.A. Standard Test Sieve series (ASTM E11 Specification)

Example of 8 and 30 sieves (8×30)
Mesh 8	Mesh 30
Example of 12 and 40 sieves (12×40)
Mesh 12	Mesh 40

U.S. Standard Sieve Number Conversion Chart to millimeters and inches

TABLE:

Mesh Number (U.S. STD. Sieve)	Opening (mm)	Opening (in)
4	4.76	0.187
5	4.00	0.157
6	3.35	0.132
8	2.38	0.0937
10	2.00	0.0787
12	1.68	0.0661
14	1.41	0.0555
16	1.19	0.0469
18	1.00	0.0394
20	0.841	0.0331
25	0.707	0.0278
30	0.595	0.0234
35	0.500	0.0197
40	0.420	0.0165
45	0.354	0.0139
50	0.297	0.0117
60	0.250	0.0098
70	0.210	0.0083
80	0.177	0.0070
100	0.149	0.0059
200	0.074	0.0029
325	0.044	0.0017
400	0.037	0.0014

What is effective particle size?

Filter media size is commonly specified in terms of effective size and uniformity coefficient, or in terms of particle size range. Effective particle size is defined as the mesh opening through which only 10% (by weight) of a representative sample of the filter media passes.

What is the uniformity coefficient?

It is the ratio calculated by dividing the mesh opening through which 60% (by weight) of a representative sample of a filter material passes by the mesh opening through which only 10% (by weight) of the sample passes.

What is the mesh size or particle size of the filter media or granular media?

Activated carbon for water treatment: 325, 200, 8×30, 12×40 and 20×50 mesh.

Activated carbon for air and gas treatment: 4×10 and 14×30

Silica sands: 10×20 and 20×30

Anthracites: #1 14×30, #1.5 10×20, #2 4×12

Zeolite: 14×40

History and development of the U.S. Standard Sieve for mesh size or particle size classification.

The US Standard Sieve Series, commonly known as the US Standard Sieve Series, was developed in the early 20th century by the ASTM (American Society for Testing and Materials). The need for a standardized grading system arose with the rise of industrialization, where consistency and accuracy in particle size became crucial for various industrial applications, including filtration.

Structure and principle of operation

The US Standard Sieve system classifies particles based on their size using a series of mesh sieves, each with a specific number of openings per linear inch. Each sieve has a numerical designation corresponding to these openings, allowing precise categorization of particles. For example, a number 4 sieve has 4 openings per linear inch, while a number 200 sieve has 200 openings per linear inch.

Importance in the classification of filter media

In the filtration industry, particle size is crucial in determining the efficiency and capacity of a filter media. Granular filter media, such as sand or activated carbon, must have a specific particle size to ensure effective filtration and prevent the passage of unwanted contaminants. The use of the US Standard Sieve allows for accurate grading, ensuring that the filter media meets the required quality standards.

Management and regulations

Maintenance and calibration of the sieves is essential to ensure accurate and consistent results. ASTM provides detailed guidelines on the care and calibration of sieves, including methods for checking the size of apertures and recommendations for cleaning and storage of sieves.

Industrial applications

In addition to filtration, the US Standard Sieve system is used in a wide range of industries, including pharmaceutical, food, mining and construction. In each of these industries, accuracy in particle classification is crucial to the quality of the final product and the efficiency of the production process.

The US Standard Sieve particle size is a mainstay in the classification of granular and powdered filter media. Its development by ASTM and its implementation in various industries has allowed standardization that guarantees quality and efficiency in numerous processes. The understanding and proper use of this system is essential for any professional working with granular or powdered materials, ensuring accurate and reliable results.

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