Optimization of screening effect in mechanical equipment

The purpose of a screener is to separate and remove oversized,troublesome, and unwanted particles from the material. Although there are many different types of screens that accomplish this in different ways, all have one common feature. All screens rely on some form of per-forated barrier or screen plate to pass acceptable fiber and reject oversize or unwanted material. The size of the perforations in this barrier is the most important factor in determining the size of debirs that will be removed for continuous operation, some means of screen plate cleaning must be used. Methods presently employed to clean the screen plate include shaking the plate, maintaining high velocity across the plate, back flushing, or, most commonly, pulsing the flow through the holes with various moving foils, paddles, or bumps. As a rule, the stability of a screen will decrease as the throughput increases. At some point when the throughput demand exceeds the capacity of the screen, the volume of rejects matted on the screen plate will plug it. By decreas- ing either the consistency or flow, or both, stability will usually be restored. A point often overiooked is that when a screen plate with smaller perforations is installed,more material will be rejected and less material accepted than with a plate of the same dimens- ions but with larger perforations. Adjustments to the flow and operation of the screen.