Machinery's Handbook, 31st Edition
Meshes, Sieves, and Screens 1069 particle size distribution. Sieves and screens are usually used for larger particle sized materials, greater than 44 micron (325 Mesh).
D S I E V E S E R I E S
A.S.T.M. E-11 SPECIFICATIONS
MICRONS 425
OPENING
0.425 MM
IN
0.0165
U S S T A N D A R D S I E V A.S.T.M. E-11 0.0059 IN OPENING SPECIFICATIONS SIEVE NO. 100
MICRONS 150
Fig. 1. Two scales are frequently used to classify particle sizes; US Sieve Series and Tyler Mesh Size, also called Tyler Standard Sieve Series . The larger the mesh number the smaller the particle size of the powder. The Tyler mesh number indicates the number of openings in the screen per linear inch. • A - 6 mesh powder contains particles that pass through a 6 mesh screen. A - 6 mesh powder has particles that measure less than 3360 microns. • A powder that is - 325 mesh has particles that measure less than 44 micron. Market Grade sieves use thicker wire than other commercial grades, and are commonly used for applications where mesh strength (and therefore screen life) is important. Mill Grade sieves use a thinner wire diameter, which provide more open area for a given mesh size. Therefore, Mill Grade sieves are used when throughput is more important than durability. Tensile Bolting Cloth uses very fine wire diameters, and thus provides the highest fraction of open area of all sieve types; it is often used for fine sifting and screen printing. A comparison of standard screen and sieve sizes are indicated in Table 2 and Table 5. Example 1: A tantalum powder has the following description: Tantalum Powder, - 325 Mesh, 3N8 Purity The minus ( - ) sign in the designation - 325 indicates that particle sizes of less than 44 micron ( µ m) (Table 1) are able to pass through a 325 mesh screen. Much of the powder may be considerably smaller and still qualify as a - 325 mesh powder, but the designation − 325 mesh simply means that the powder will pass through a 325 mesh screen. The 3N8 Purity indicates a purity of 99.98% relative to other rare earth powders; similar ily, 2N5 indicates 99.5% purity, 5N8 indicates 99.9998%, and 6N indicates 99.9999%, etc. Example 2 : illustrates two stacked screens. If a powder is required to fall within a specified max/min range of sizes, two mesh sizes maybe specified such as in the following: Tantalum Powder, − 40+100 Mesh, 3N8 Purity The - 40 designation indicates that the powder will pass through an 40 mesh screen, and the designation +100 indicates that particles are trapped (do not pass through) by a 100 mesh screen. Thus - 40+100 indicates a range of particle sizes small enough to pass the 40 mesh and too large to pass the 100 mesh screen.
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