Slotted (or sleeper) sieves are used primarily in the process of separating various raw materials into solid and liquid fractions.

When the feedstock enters (1) the equipment (e.g. separator), the liquid portion of the feedstock is separated through the sieve (2) by gravity. An auger (3) within the sieve allows flow within the sieve. The required outlet pressure (4) is created by the pressing mechanism. This ensures a dry solids concentration of 35% to 45% and the resulting solid fraction does not require additional dewatering.