Screen Filters, SAF Series

The filtering process

Raw water enters the filter inlet through the coarse screen, which protects the cleaning mechanism from large debris. The water passes through the fine screen, trapping dirt particles which accumulate inside the filter. Clean water flows through the filter outlet.

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 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, which spirals across the screen. The open exhaust valve creates a high-velocity suction stream at the nozzle’s tip that vacuums the filter cake from the screen. During the self-cleaning process, which takes from 20 to 40 seconds, filtered water continues to flow downstream.

The control system

Two types of control boards are available for SAF filters: PLC or electromechanical relay and timer.

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.