How the Sigma Filter Works
The Amiad “Sigma” filter is an automatic filter, with multiple screens operated by a single hydraulic turbine mechanism.
With a capacity up to 120 m3/h (528 gpm) and from 80-300 micron filtration degree. Inlet/Outlet connections are
100 mm (4”) diameter, and exhaust valve is 50 mm (2”).
Raw water enters from the filter inlet and passes through the multi-screens. Clean water flows through the filter
outlet. The gradual dirt buildup on the inner screen surface causes a filter cake to develop, with a corresponding
increase in the pressure differential across the multi-screens. A pressure differential switch (hydraulic or electric)
senses the pressure differential and when it reaches a pre-set value, the self-cleaning process begins.
The Control System
The “Sigma” operation and cleaning cycle is controlled and monitored by a hydraulic rinse control, or an electronic
battery /AC controller.
During the self-cleaning cycle the rinse control operates the exhaust valve by means of an hydraulic command, and
when the cycle is complete, it automatically closes the exhaust valve and waits for the next cycle. In the case of the
electronic controller, the self-cleaning cycle is triggered by the DP switch, then the AC or DC controller switches the
solenoid to open or close the exhaust valve by means of a hydraulic command, when cycle is complete, the controller
will shut the exhaust valve and wait for another cleaning command.
The self-cleaning cycle begins under any one of the following conditions:
- Receiving a signal from the Pressure Differential Device - which is preset at 0.5 bar.
- Time interval parameter set at the controller (electronic controller only).
- Manual Start, triggered by 3 way ball valve or via electronic controller keypad.
The electronic controller also provides:
- Flush cycles counter
- Alerts output – low battery, DP cycle