Test sieving procedures

Wet Sieving by a Mechanical Flushing Procedure. The sieve residue is the portion of coarse particles that cannot be washed through a specified test sieve with water. The result depends on the mesh size of the sieve. For standards, see Table 1 ( Residue on sieve Mechanical method ). Apparatus Mocker s apparatus. 

Reciprocating sieve-plate columns, where a reciprocating motion is imparted to the plate assembly, have been suggested by Karr and Lo (1976). In such columns, a baffle plate can be employed to minimize axial mixing, and reciprocation speed can be varied over a wide range. Karr and Lo have discussed procedures for scale-up and have tested this procedure with columns up to 90 cm in diameter. HETS increases with column diameter and shows an optimum with respect to reciprocation speed. For a column 90 cm in diameter,... 

Complete instructions and procedures on the use and calibration of testing sieves are contained in ASTM STP447B [7]. Contents include analytical methods, information relating to wire mesh, perforated plate and micromesh sieves, dry and wet testing and other methods. This publication also contains a list of all published ASTM standards on sieve analysis... 

Screen Analysis of the Substrate. The milled cellulose was screen analyzed in a Ro-Tap Testing Sieve Shaker (The W. S. Tyler Company, Cleveland, Ohio) using a series of 40, 60, 100, 120, 170, 200, and 270 mesh U.S. Standard Screens sifting for 45 min. plus an additional 5 min. after the first weight to check the reproducibility of weights of the screened fractions. Both the weights checked very well. The same procedure was followed in the case of SF, SF-H, SF-HM, SF-MH, and Sweco 70 samples, all of which were subsequently tested. Summary of screen analyses reports is presented in Table II and Figure 9. 

Procedures for test sieving, both wet and dry, are prescribed in standard specifications (ISO 2591, 1989 BS 1796, 1990). Methods for the analysis of sieve test data are described in section 2.14.4. 

Most countries have standard sieve specifications and sieve analysis procedures. These specifications and procedures are usually generic and can be used for a wide variety of products, including fertilizers. The ISO has a series of international standards for test sieves [10] including (1) Test sieves - Woven metal wire cloth and perforated plate - Nominal sizes of apertures (ISO 565) ... 

A typical testing procedure involves several steps. First, the selected number and size of sieves are stacked upon one another, with the largest openings (inversely related to mesh per inch) being at the top of the stack, and beneath that a pan to collect the particles finer than the smallest sieve. The known amount of powder to be analyzed is then placed on the top sieve and the set is vibrated in a mechanical device for a predetermined time period. The results are obtained by weighing the amount of material retained on each sieve and on the collecting pan. The suction method uses one sieve at a time and examines the amount retained on the screen. In both methods the data are expressed as frequency or cumulative frequency plots, respectively. 

The most common method for measuring bulk density is to pour the powder into a tared graduated cylinder and measure the bulk volume (Vb) and mass of the material. Other methods, however, have been employed to ensure reproducibility, and a standard procedure has been reported [62,64]. For this testing, a sample of 50 g is passed through a U.S. Standard No. 20 sieve and is poured into a 100-ml graduated cylinder. The cylinder is then dropped from a height of 1 inch onto a hard surface three times at 2-second intervals. The volume of the powder is then read and used to calculate the bulk density. This three-tap method was found to give consistent results between laboratories. 

Finally, one aspect that can pay a role in compositional studies is the sieve (screening) analysis. Like all petroleum products, sampling is, or can be, a major issue. If not performed correctly and poor sampling is the result, erroneous and very misleading data can be produced by the analytical method of choice. For this reason, reference is made to standard procedures such as the Standard Practice for Collection and Preparation of Coke Samples for Laboratory Analysis (ASTM D346) and the Standards Test Method for the Sieve Analysis of Coke (ASTM D293). 

---