water enters the filter through the inlet (1) and then passes through
the coarse screen (2) from the outside in. It flows from the inside of
the coarse screen to the inside of the fine screen and then passes
through the fine screen (3) from the inside out. Dirt is collected on
the inside surface of the fine screen. The clean filtered water then
exits through the filter outlet (4) and on to the system.
As the dirt or cake builds up on the inside surface of the fine
screen, the pressure drop across the screen increases. When the pressure
drop (the DP or differential pressure) reaches a preset level of 0.5
bar (7 psi), the filter controller starts a flush cycle by opening a
flush valve on the flush line (5). This flush valve exhausts the drive
chamber to atmosphere at “0” psi.
The flush line (5) is connected to the drive chamber which is
separated from the filtration chamber by a drive chamber partition (6).
However, the dirt collector (7) (a hollow pipe with dirt collector
nozzles) extends through the partition (6), thus providing a “path” from
the dirt collector nozzles (8) through the hydraulic drive (9), into
the drive chamber and out the flush line (5) to atmosphere. The pressure
around the dirt collector nozzle (8) is the pressure inside the filter
and as water flows through the “nozzle orifice,” it drops to “0” psi
when it leaves the flush line (5). This creates an aggressive “suction”
at the dirt collector nozzle (8) opening. The dirt collector nozzle (8)
clearance at the fine screen (3) is very small so the extreme low
pressure at the nozzle opening creates a vacuum causing backflow to pull
the dirt from the fine screen (3).
The hydraulic drive (9) has opposite facing jets near its ends. Water
jetting out of these openings (coming from the dirt collector nozzles
(8)) creates a reaction force (like a pin wheel) which rotates the drive
(9) and the dirt collector (7). As the dirt collector (7) rotates, each
dirt collector nozzle (8) cleans a band on the fine screen (3). As the
dirt collector (7) rotates, the reverser (10) (works like the level
winder on a fishing reel) causes the hydraulic drive (9) / dirt
collector (7) / dirt collector nozzle (8) assembly to move back and
forth on a controlled path. This ensures proper overlap for 100%
cleaning of the screen's inner surface.
The rotation governor (11) helps control the rotation speed of the
dirt collector (7) assembly. The balance tube (12) helps balance the
transverse pressure on the assembly. A magnet located on the end of the
balance tube repels the reverser indicator (13) which provides visual
indication of the dirt collector (7) assembly movement. This indicates
that that the entire cleaning system is operating properly during the
After a preset time, the flush valve closes and the flushing cycle is
complete. Minimal water is used for each flush, and the filter
continues to supply water to the system during the flush cycle.