DFW Disc Filter (Stacked Disc Filter)

Disc Principle:

The surface of the filter disc is engraved with fine grooves, and the groove directions of adjacent discs differ in angle, forming many groove intersection points (see right figure). The number of groove intersection points varies with different disc specifications, ranging from 12 to 32, depending on the filtration precision of the disc. These intersection points create numerous cavities and irregular passages, causing turbulence and particle collisions and agglomeration, making it easier for particles to be intercepted at the next intersection point. Therefore, even if some particles pass through the initial intersection point, they will eventually be intercepted by subsequent intersection points. When a large amount of impurities accumulate in the grooves between discs, the filter device automatically opens the pressed discs by changing the direction of the inlet and outlet water flow and sprays pressurized water to drive the discs to rotate at high speed. The discs are cleaned by the flushing of pressurized water and centrifugal force from rotation. Then, the water flow direction is changed back to restore the initial filtration state.

System Working Principle:

1. Filtration Process

(1) The disc is pressed tightly by the pressing force formed by the pressure difference between the upper and lower chambers of the diaphragm, forming a compact filter element to prevent impurities in the water from penetrating;

(2) Raw water enters the filter and passes through the filter element from outside to inside; suspended impurities are intercepted on the outside and between the discs.

Illustration One

2. Backwash Process

The controller sends a signal to close the inlet water and open the drainage, while the upper chamber of the diaphragm is also depressurized simultaneously.

(1) Clean water filtered by other filter units enters the outlet of the backwashing filter from the opposite direction;

(2) The check valve is pressed by water pressure, allowing water flow only into the four backwash pipes;

(3) Pressurized water is sprayed from nozzles installed on the backwash pipes;

(4) The pressurized water in the backwash pipes also enters the pressing chamber, pushing the pressing cover upward and loosening the discs pressed by it;

(5) Water jets sprayed tangentially drive the loosened discs to rotate rapidly, flushing away intercepted impurities;

(6) Backwash water carries flushed impurities out through the drainage outlet;

Illustration Two

Raw Water Quality Analysis for Disc Filter:

1. Raw Water Quality Classification:

A. Excellent water quality: city tap water, well water drawn from stable aquifers;

B. General water quality: circulating cooling water, surface water treated by sedimentation, wastewater effectively sedimented and fully biologically treated;

C. Poor water quality: groundwater drawn from very poor quality aquifers, wastewater effectively sedimented but untreated or minimally biologically treated, surface water with heavy microbial growth;

D. Very poor water quality: well water drawn from very dirty or iron-manganese rich wells, surface water affected by floods and untreated by sedimentation, wastewater untreated by sedimentation and biological treatment.

Different incoming water qualities greatly affect the filter's operating cycle. Usually, when selecting the system, the backwash interval should not be less than 1 hour.

2. Filtration Precision Selection:

Choosing the filtration precision of the filter disc is crucial to ensure the stacked disc filter functions effectively in the entire water system. Only reasonable and correct selection can meet subsequent water quality requirements. The table below recommends filtration precision for common centralized filtration applications.

Raw water quality, required filtration precision after filtration, and hourly water output are the basis for selecting our filtration system.

40 mesh: for sprinkler irrigation

80 mesh: for micro-sprinkler and drip irrigation (maze-type drip tape)

120 mesh: for drip irrigation

150 mesh: for drip irrigation

Disc Filter Product Selection Table

Disc Filter User Manual

1. The stacked plate filter can be used under a working pressure of less than 1.0 MPa.

2. To facilitate disassembly and maintenance of the stacked plate filter, it is recommended to install control valves at the inlet and outlet (for single filters, only install a valve at the inlet).

3. The stacked plate filter is equipped with one inlet and two outlets.

4. To monitor the water pressure during operation, a pressure gauge can be installed at the inlet. If the water supply pressure is unstable, install a pressure regulating valve to ensure stable pressure.

5. After installing the stacked plate filter, open the drain valve first to discharge air before use. Close the drain valve once the air is expelled.

Stacked plate filter cleaning procedure:

1. Close the inlet valve and open the drain valve to empty the accumulated water in the filter.

2. Open the clamp lock handle, remove the clamp, and open the upper and lower filter housings.

3. Hold the filter cartridge cap and unscrew the filter cartridge assembly counterclockwise.

4. Clean the stacked plates: Hold both ends of the filter cartridge assembly with both hands, unscrew the disc frame counterclockwise, pull the frame and the inner core apart to fully loosen the plates, immerse them in water and rinse repeatedly to thoroughly clean the impurities adsorbed on the plates. Then reassemble in the reverse order of disassembly, screw clockwise onto the upper housing, and ensure the four hooks on the filter cartridge assembly are properly installed on the upper housing.

5. When installing the upper and lower housings, check if the sealing gasket is intact. Replace it promptly if it is damaged.

6. Finally, install the clamp and tighten the handle (if the clamp lock handle is too loose after tightening, adjust the bolt above it).

7. Before putting into use, open the inlet valve to check and confirm there is no water leakage, then it can be used normally.

 Dirty water enters from the filter inlet, first passing through the coarse filter screen to remove larger particles, then reaching the fine filter screen. During filtration, the fine filter screen gradually accumulates dirt and impurities from the water, forming a filter impurity layer. Because the impurity layer accumulates on the inside of the fine filter screen, a pressure difference forms on the inside and outside of the fine filter screen. When the pressure difference of the self-cleaning filter reaches the preset value, a switch signal is sent to the control box PLC system to start a cleaning cycle. Cleaning process: The cleaning mechanism of the fully automatic negative pressure suction filter is a stainless steel spiral up-and-down moving suction scanner. It is hollow in structure, with several suction nozzles vertically distributed at certain distances along its axis. The inside of the suction scanner communicates with the 3” drain valve. When the drain valve opens, the pressure difference between the internal water pressure of the filter and the external atmospheric pressure generates strong suction at each suction nozzle. At each suction nozzle, water flows rapidly from outside to inside in reverse, washing impurities attached to the inner wall of the filter screen into the suction nozzle, through the hollow shaft of the suction scanner, then discharged through the drain valve, completing the cleaning process which takes about 30-60 seconds. At this time, the pressure difference returns to normal, the cleaning process ends, and filtration resumes. During cleaning, the system continues to flow.