Facts & Figures Book - KPI-JCI

SAND CLASSIFYING TANKSPurpose: Classification is the sizing of solid particles (typically– 3 ⁄8” or -#4 mesh) by means of settling. In classification,the settling is controlled so that the fines or undersize materialwill flow away with a stream of water or liquid, while thecoarse or oversize material accumulates in a settled mass.By applying the principles of settling and classification inthe classifying/ water scalping tank, the following functionsare performed:1) Reject undesirables – remove clay, silts, slime andexcess fine particles2) Separate desirable sand particles so that they can becontrolled3) Reblend separated material into correct gradationspecifications4) Production of two different specification productssimultaneously and an excess product5) Remove excess waterFeed to a classifying tank is typically in the form of a sandand water slurry. The slurry feed can come from severalsources, but is generally from a dredging or wet screeningoperation.CLASSIFYING TANKS ARE NECESSARY WHEN ANY ONEOF THE FOLLOWING CONDITIONS EXIST:1) Feed material gradations fail to meet the allowableminimums or maximums when compared to the materialspecifications to be produced2) Sand feed gradations vary within a deposit3) More than one specification product is desired4) Excessive water is present, such as from a dredgingoperation119Washin g/Classifyin g