Automatic backwashing strainers are a cost-effective alternative to duplex strainers for high flow rate applications where removing and cleaning large, heavy strainer baskets would be difficult. They are also ideal for remote locations with limited personnel available to service simplex and duplex basket strainers.
Application Considerations
Because these strainers use about 5% of the filtered liquid during the backwashing process (which can last several minutes), they are typically used for water filtration or other liquids not considered scarce or expensive.
- Operating Pressure: Designed to operate between 30 PSIG and 285 PSIG.
- Retention Range: Best suited for coarse retentions in the ¼" range down to 100 mesh (150 microns). Mesh-lined elements are available for retentions as fine as 75 microns.
- Materials: Standard construction includes cast iron, carbon steel, and 316SS. Hastelloy is available for warm sea water applications.
Typical Applications
- Water Treatment: Removing impurities from raw water sources (rivers, lakes) before treatment and use in industrial or agricultural irrigation.
- Industrial Process Water: Filtering large quantities of clean water used for cooling and cleaning in power generation, chemical manufacturing, primary metals, and food/beverage production.
- Fire Protection Systems: Removing debris and sediment from water used in fire sprinklers and standpipes to ensure emergency readiness.
How the System Works
Filtration Mode: Flow enters the strainer body and moves upwards into the stationary element. Internal geometry evenly distributes the flow across the inner circumference. The liquid passes through the element, exiting the outlet nozzle. Particulates fall to the vessel's bottom or are held against the element's surface by differential pressure.
Backwash Mode: The cycle is actuated by manual override, differential pressure, or a programmable timer. When initiated:
- A drain valve opens and a motor rotates a hollow shaft containing a vacuum nozzle inside the filter element.
- As the nozzle sweeps the inner circumference, differential pressure (system vs. atmospheric) forces clean liquid to reverse-flow through that specific section.
- Debris is dislodged, vacuumed through the hollow nozzle shaft, and flushed out the drain.
- The robust motor and nozzle arm break up sticks and organic material that may be stuck.
Maintenance & Accessibility
Periodically, large debris must be cleared from the bottom of the strainer. The straining element and backwash nozzle assembly are attached to the top section, allowing it to be easily lifted off as a single unit for inspection. An optional manway can be installed to facilitate clean-outs without full disassembly.
Automatic Control Packages
All packages can be customized with stainless-steel wetted parts, explosion-proof components, and alternative control methods.
| Package | Motor Specs | Included Features |
|---|---|---|
| ACS-1 (Base) |
120V / 1 Ph / 60 Hz | NEMA 4 panel box, adjustable timer, dP override, 10 Amp control relay for valve, status indicator lights, manual selector switch, single element dP switch (dual optional), contact terminals for motor starter & alarm. |
| ACS-2 | 120V / 1 Ph / 60 Hz | Includes all standard features of the ACS-1 package plus a motor starter inside the NEMA 4 panel. |
| ACS-3 | 460V / 3 Ph / 60 Hz | Includes all features of the ACS-1 package plus a control voltage transformer and motor starter inside the NEMA 4 panel. |
Note on Valves: 2” to 16” strainers utilize electrically actuated standard port ball valves (brass body, 316SS ball/stem). 18” to 24” strainers feature flanged carbon steel valves. Pneumatically actuated valves with NEMA 4 pilot solenoids are also available.
Key Automatic Strainer Features
- Designed/constructed to ASME Section VIII, Division 1 (ASME Code Stamp available).
- Seismic qualification available.
- Unique quad shaft seal prevents process media leaks down the strainer sides.
- Motor, gear reducer, cover, and internal mechanisms lift off as a single unit.
- Zero bypass of contaminants (element caps are epoxy sealed to screen media).
- Cover O-ring permits resealing without time-consuming gasket replacements.
- Manual override is a standard feature.
