Miller Magazine Issue: 121 January 2020

66 ARTICLE MILLER / JANUARY 2020 this regard, acceleration measurements and displacement measurements were performed on a xxxx type and xxx configured screen to determine the regime of the sieves and to de- termine the tension levels. ACCELERATION MEASUREMENTS Acceleration measurements were per- formed on three axes perpendicular to each other since the first operation of the sieve and the maximum acceleration component was measured as 5.91 g. In sieve and simi- lar dynamic systems, a certain period of time is required for the system to enter the regime and exhibit a stable dynamic characteristic. Table 1 displays the maximum compound acceleration values measured after obtaining stable dynamic behavior in sieves with different passag- es. As seen in Table 1, maximum compound acceleration values increased with increasing number of passages. The main reason for the increase in acceleration values can be attributed to the increase in dimensions along with the number of passages and in particular the in- crease in drive mass. On the other hand, the maximum compound acceleration value was measured as 3.72 g when the sieve was stopped. • Measurements of screen displacement The movement of the sieve after starting the sieve was recorded and monitored time-dependently for 45 minutes. This time-dependent movement is presented in Figure 3. As shown in Figure 3, the circular move- ment started with the first movement of the screen. However, the movement obtained is rather irregular and it is seen that instead of the ideal circular motion of 60-65 mm diame- ter, a circular movement of 30-35 mm diame- ter is formed. During the first 10- minute peri- od, the movement became clear. However, it takes a period of about 40-45 minutes for the sieve to enter the regulation and to move in concentric circles. 4. Results The measurements made on the sieve showed that the maximum compound accel- eration value was dependent on the number of passages and that the value in 4-passage sieve was 5.9 g while the figure was at the level of 6.55 g in 10-passage system. It can be consid- ered that this change in question is due to the increase of the moving mass value due to the increase of the number of passages and the change of the sieve geometry. In this case, it is concluded that the sieve designs should be optimized to perform the sieving process with the highest efficiency and to provide minimum acceleration values. It was observed that after the sieve was oper- ated, the stability was obtained within approxi- mately 40-45 minutes and at the end of this time the sieve started to draw concentric circles in 60-65 mm diameter. In the sieve design, ena- Figure 2. Modern sifters used in present day [5] Number of Passages Maximum Compound Acceleration (g) 4 5,9 6 6,1 8 6,39 8+2 6,51 10 6,55 Table 1. Acceleration values obtained depending on the number of passages