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filtration systems
DESCRIPTION OF FILTER OPERATION
Filtering process:
The SAF-4500 is a sophisticated yet easy-to-operate automatic filter, with a self-cleaning mechanism driven by
an electric motor. The SAF-4500 is designed to work with various types of screens in filtration degrees from 500
to 10 micron, and is available in 4", 6" and 8" inlet/outlet diameter.
The water enters through the inlet pipe into the coarse screen from outside in, and through the fine screen from
inside out. The "filtration cake" accumulates on the fine screen surface and causes head loss to develop.
The coarse screen is designed to protect the cleaning mechanism from large dirt particles. It should not
accumulate large quantities of suspended solids and is not cleaned automatically.
Self-cleaning process:
The SAF-4500 will start the self-cleaning process when the pressure differential across the screen reaches a
pre-set value or a predetermined lapse of time.
Cleaning of the filter element is carried out by the suction scanner which rotates in a spiral movement while
removing the filtration cake from the screen and expels it out through the exhaust valve.
The rotation of the scanner is operated by a 2-way (fwd/rev) drive unit that is attached to the scanner by a
threaded shaft which provides the linear movement.
The exhaust valve is activated for the duration of the cleaning cycle by a 3-way solenoid. During the self-
cleaning process, which takes approximately 20 seconds, filtered water continues to flow downstream.
Different modes of filtration:
The filtration system may be found in one of the following modes:
1. Filtering mode: This is the normal function condition. Flushing is not occurring and the power light on the
control board is lit.
2. Flushing mode: A mode in which the flushing process is in progress. The motor and exhaust valve are
operating according to the program.
3. Continuous flushing mode: It is possible to activate the self-cleaning mechanism continuously by changing
the switch near the timer in the control board to "CONT." position.
4. Malfunction mode: During malfunction mode the self-cleaning operation is stopped, the malfunction light on
the control board is turned on and an external output is activated with 24V AC.
The filtration system may enter a malfunction mode in the following cases:
1st. When there is a continuous signal from the pressure differential switch for a duration of more than the pre-set time.
This means that the self-cleaning process is not successful.
2nd. When the motor protector was activated, either manually or due to over load.
3rd. As a result of a malfunction in the limit switches.
Initiation of self-cleaning:
The filter will enter the self-cleaning process as a result of any of the following causes:
1. A signal from the Pressure Differential Switch (PDS) - The PDS which is situated on the filter body, sends an electric
signal when the pressure differential across the screen reaches the pre-set value (usually 0.5 bar =7 psi). The control
board registers the signal and operates the flushing process according to its program.
2. Manually pressing the "TEST" push button at the control board.
3. The TIMER installed in the control board allows operation of self-cleaning process at time intervals that can be set up,
independent from the head loss factor. The timer resets after every flushing cycle.
4. A signal from Continual flushing switch - This switch in the control board allows operation in continuous flushing mode;
meaning, the filter is flushing itself all the time regardless of flow rate or water quality.
Control system:
Two types of control boards are available: PLC Type and Relay Type. See Appendix A or B for details.