How is the number of sieve holes determined?
Food classifiers are commonly used size classifiers and weight classifiers, and the size classifiers are mostly designed as drum classifiers. Drum classifiers are one of the most widely used classifiers in food classifiers. Most fruit grading machines adopt this form, and the size of the drum perforation determines the level of grading, so how to determine the number of sieve holes of the drum? Let’s take a look: the drum design, let’s take fruits as an example for calculation, consider According to the difference in fruit size and shape, the grading of the drum is set to 6 levels. In the actual classification, the adjacent two-stage hoppers can be combined into one level to meet the needs of different classifications. The design now uses 5 screen drums and 6 grades. 1. Determining the production capacity of the total number of drum holes G can be calculated by the following formula: G u003d 3600zλm/1000×1000 where: z is the total number of holes on the drum; G is the production capacity; λ is the material dropped from the sieve holes in the same second The coefficient of is different depending on the sorting model and the nature of the material. The drum type can be 1.0% to 2.5%; m is the average quality of the material. According to the design requirements, the parameters Gu003d12 t/h, mu003d400g, λu003d2.0% can be calculated as z u003d1000×1000G/3600λm u003d1000×1000×12/3600×0.02×400 u003d417 (units) 2.3 .3 Determination of the drum diameter D, length L, the number of rows P at each level, and the number of holes Z in each row. When the production capacity is known, the Z obtained by formula (2-1) is the number of holes required on the drum . However, due to the different sieve apertures at each level and the same drum diameter, the total number of holes cannot be evenly distributed among the levels, but should be divided into several levels with different diameters according to the requirements of the process, and then the number of rows in each level is determined according to the number of levels. The number of sieve holes in each row of the same level. If the drum is unfolded into a plane, the relationship is the number of holes per level u003d the number of rows × the number of holes in each row, the length of each level u003d (the diameter of each level of sieve holes × the number of holes in each row) + (the gap between sieve holes × the number of holes in each row) Then the circumference of the drum u003d (number of rows × aperture of each level) + (number of rows × aperture) theoretically, the sum of the number of holes in each level is equal to the total number of holes Z, and the sum of the length of each level is the designed length of the drum, but In this way, the diameters of the rollers at all levels of the design calculation are different and cannot be connected together. Therefore, generally the first stage with the larger diameter of the drum is taken as the diameter of the whole drum. After initially determining the diameter and length of the drum, use D:Lu003d1:4～6 to check. If it is not within this range, you should readjust the number of rows or holes in each stage until it reaches this ratio range. Generally, if L>6D, you can appropriately increase the number of rows and reduce the number of holes in each row; if L>6D, you should increase the number of holes in each row and reduce the number of rows. Now based on the demand for sorting the required fruits, the sieve diameter is estimated as follows: Table 1 the parameter of screen size Table 2 the parameter of screen size ai axial distribution proportional coefficient bi first level 80×40151/81/2 second level 85×45201/21/4 third level 90×50251/41/8 fourth level 95×55301/81/8 fifth level 100×60351/81/82.3.4 Calculation of the number of sieve holes at each level (1) The number of sieve holes at each level Z1u003dai bi Z. (2-2) In the formula: Z1—the number of each sieve hole, each; ai—the proportional coefficient of the particle size distribution of the raw material; bi—the proportional coefficient of the distribution of the raw material along the axial direction of the drum; Z. —Number of reference holes, each. (2) The number of reference holes is Z. u003dZ/∑ai bi (2-3) then Z. u003d417/(1/8×1/2＋1/2×1/4＋1/4×1/8＋1/8×1/8＋1/8×1/8)u003d1668 (units), then Z1u003dai bi Z . u003d1/8×1/2×1668u003d104Z2u003dai bi Z. u003d1/2×1/4×1668u003d209Z3u003dai bi Z. u003d1/4×1/8×1668u003d52Z4u003dai bi Z. u003d1/8×1/8×1668u003d26Z5u003dai bi Z. u003d1/8×1/8×1668u003d26 The readiness of the sieve perforations determines the accuracy of the classification and is also an important content of the classification.