Screen Filters, EBS Series

The filtering process

Raw water enters from the filter inlet (1) and passes through the screen (2). Clean water flows through the filter outlet (3). The gradual dirt build up on the inner screen surface causes a filter cake to develop, with a corresponding increase in the pressure differential across the screen. A pressure differential switch (4) senses the pressure differential, and when it reaches a pre-set value the cleaning process begins.

The self-cleaning process

Filter cleaning is carried out by the suction scanner (5), which spirals across the screen. The open exhaust valves create a high-velocity suction stream at tip of the nozzles that vacuums the filter cake from the screen. During the self-cleaning process, which takes approximately 30 seconds, filtered water continues to flow downstream.

The control system

The filter operation and cleaning cycles are controlled and monitored using a programmable logic controller (PLC). The PLC allows maximum flexibility in control options and has many additional features that can be incorporated according to customer need. During the self-cleaning cycle the PLC controls a solenoid that operates the exhaust valve by means of a hydraulic command or compressed air.

The self-cleaning cycle begins under any one of the following conditions:

1. Receiving a signal from the pressure differential switch

2. Time interval parameter set at the control board

3. Manual start

The control board also provides:

• Optional continuous flush operation mode
• Flush-cycle counter
• Alarm output – may be used to open a bypass, shut off a pump, etc.