Water treatment screen cleaning rake insertion, monitored and linked to control system

摘要

Screen comprising of a number of vertical rods which straddles a water conduit in a water treatment plant inlet is cleaned using a powered rake with reversible drive. The foot projections on the rake raise solids to an upper position from which they are thrown into a collector skip by an upward lever action, which is then reversed and the rake lowered for another cycle by hooking under and insertion into the trapped solids, and begins to lift under power. The rake drive is equipped with a sensor which measures the resistance to upward motion and which is interrupted at a defined upper threshold value. Following the rake re-insertion and commencement of the lift, the angle between the rake and grate and the degree of insertion into the trapped solids is monitored, and that if a pre-determined rake angle and penetration have not been reached, the rake is withdrawn, lowered and reinserted. This operation is repeated until the signals received by the control mechanism indicate that the combination of angle, insertion and load are within acceptable limits, whereupon the lift and subsequent load ejection are completed. A counter mechanism records and limits the number of attempted but unsuccessful insertion and lift cycles before triggering an alarm and stopping further attempts.