How does the Screen Basket Operate in a Pressure Screen?

The screen basket, as the most precise and crucial heart of the pressure screen, has a significant impact on the screening of pulp and the final quality of paper. First, the unscreened pulp enters the upper separation chamber of the pressure screen tangentially through the pulp inlet pipe. Heavier objects are sagged and discharged at the heavy slag outlet under the action of centrifugal force. The slurry flows through the circular weir plate and then enters the screening zone of the pressure screen basket and rotating rotor. The close cooperation between the rotor and the screen basket creates negative pressure and shear force, which effectively blows away, peels away and removes impurities from the fibers. Qualified fibers are led out through the screen holes (slits) from the good slurry outlet, while non-compliant fibers continue to move downward and are discharged from the bottom slag discharge pipe of the pressure screen. The rotor surface inside the screen basket rotates at high speed and has many protrusions. During operation, a local negative pressure is generated behind each protrusion, which achieves the effect of purifying the screen holes on the screen basket surface.

Types of Pressure Screen Basket

Screen baskets come in two structural forms: plate-type corrugated and rod-type corrugated.

Plate type corrugated screen basket: Its screen plate is made of stainless steel and is divided into two types: drilled screen basket and slotted screen basket. Corrugated grooves are opened on the surface of the screen plate that comes into contact with the pulp, which allows fibers to pass through the screen holes and slots easily, effectively separating qualified fibers from impurities and fiber clumps, thereby improving screening efficiency and obtaining high-quality pulp. The screen plate is drilled, milled, and polished to achieve a high degree of smoothness. The outer surface is welded with reinforcing rings to give the screen basket sufficient strength and rigidity. It is fixed with flanges on top and sits inside the cylinder below, resulting in a sturdy structure and stable operation.

Rod type corrugated screen basket: It is composed of a large number of special wedge-shaped bars, which are evenly embedded in the grooves of multiple ring plates along the circumference. The top is connected to the cylinder by a flange. The bottom is a cone shape, and the screen basket surface is corrugated. The strength of the bars is significantly improved compared to milled slits. Furthermore, after surface hardening treatment, the screen basket has a longer service life, making it a currently advanced structural design.

Pressure Screen Basket Selection

How to choose the right pressure screen basket? The selection of screen basket size mainly considers the properties of the paper stock and the required paper quality. For the production of high-grade paper from long fibers or when the paper stock contains a lot of light impurities, a slotted screen basket is more effective. A drilled screen basket is effective for flaky and slender impurities, with small apertures and high efficiency, but it has low production capacity and is prone to clogging. However, this can be solved by adjusting the throughput appropriately. This facilitates micro-turbulence in production, allowing more fibers to pass through the pores before the fiber layer forms.