Despite all of the pre-screening technology employed at raw cooling water intake sites, it is clear that additional filtration is often required to avoid macro fouling of the units served. The solution to this problem is provided by the Automatic Debris Filter System (ADFS).
The ADFS is designed to effectively prevent macro fouling by fibrous, course and marine life debris (larger than the selected filter perforation size), by capturing and ejecting all debris in an optimal manner. The optimal cleaning capability is achieved through the incorporation of dedicated suction ports for the two basic classes of water borne debris (course and fibrous).
When debris buildup creates the critical predetermined differential pressure across the filter, the evacuation sequence is initiated. The valve on the debris evacuation pipe automatically opens and the debris evacuation aparatus is actuated. The differential pressure at the heads creates the vacuum by which all debris is evacuated. The filter continues to clean itself until the monitor indicates a clean condition exists. The rotation of the conduit then is automatically stopped and the valve on the evacuation pipe closed.
The debris filter is controlled by a PLC based local control panel. The front of the control panel has a mimic diagram and all the controls and instrumentation required to operate the system.
The basic structure of the debris filter is illustrated on the left. The filter membrane (1) is cone shaped with debris laden water entering on the concave side. The size of the filter element perforations are supplied according to debris conditions. A debris evacuation conduit is located on the inlet side (2). The conduit is set into bearings at its extremities and is rotated by a motorized drive mechanism(6)
The conduit features one or more slotted suction heads (3) for removing fibrous material captured by the filter and impinged on the filter element surface. A broader suction head is located (4) at the downstream end of the conduit to extract larger coarse and marine type particulates. The slotted heads have flexible sealing lips (5) which concentrate suction on the filter surface directly at the point of treatment. Due to the rotation of the heads, the screen angle and flow direction, larger coarse debris is conveyed to the suction head (4) at the apex of the filter for evacuation. The debris evacuation pipe (7)is opened or closed by the built in valve (8). A differential pressure monitor (9)continuously assesses the amount of debris collected on the filter element and controls the operation of the debris evacuation apparatus.