Usually, when the slurry enters the inside of the sieve drum with a certain pressure in the tangential direction, it will move from top to bottom, and the good slurry passes through the sieve hole under the pressure difference between the inside and outside of the sieve drum.
There are generally 2-3 blades on the vertical rotor screen rotor, and the clearance between the rotor surface of the rotor blade and the screen drum is very small. When the rotor moves along the surface of the screen drum, the pressure difference of the slurry near the head of the rotor increases. As the gap between the tail and the screen drum increases, local negative pressure appears in this area. When the negative pressure is generated so that the absolute value of the slurry pressure inside and outside the screen drum is equal, the slurry stops passing through the screen hole, and when the negative pressure continues to increase, the good slurry outside the screen drum returns to the screen drum through the screen hole, acting as a reaction against the slurry and coarse fibers adhering to the screen hole. This ensures the normal operation of the screen. At the rear edge of the rotor, the resulting negative pressure is larger. After the rotor passes through, the negative pressure decreases, and the slurry relies on the pressure difference and the push of another rotor, and flows outward again to start the next cycle.
The negative pressure caused by rotor movement depends on the rotor section shape and its distance from the inner wall of the screen drum. The clearance of the screen is proportional to the size of the negative pressure, the square of the rotor speed and the number of rotor passes.
