Screening means to separate and remove solid impurities from the stock raw material solution of virgin or recycle pulp. Generally, these solid impurities differ from the fibers in size, shape, volume and deformation. These impurities are non-paper substance such as plastic, Styron foam, stickies or paper flakes or irregular fiber bundles.
There is various type of Screening equipment use in stock preparation system of the paper mill. Such as –

1. Vibrating Screen
2. Turbo Separator / Turbo Screen
3. Coarse Screen
4. Fine Screen / Pressure Screen

Purpose of Screening-
The amount of dirt separation depends on the size, shape, size variability of the dirt, as well

as the amount of dirt that accumulates on the screen at the same time. Generally, hole diameter of hole type screen is 01-03 mm and the width of the slot is 0.10 to 0.25 mm. Since the fiber has an average thickness of 10-50 microns (µm) and a length of 0.5-2 mm, the fiber can easily pass through these holes or plots. If an object is not variable in its shape and is larger in length and volume than the sieve opening, it must stick to the screen and cannot enter. Moreover, the amount of screening varies depending on the number of pores inside the screen, the fiber flow pattern, and the shape variability of the dirt substance.