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Automatic Strainers

2596 automatic strainerback washing strainer cutawayAutomatic strainers are a cost effect alternative to duplex strainers for high flow rate applications which would complicate removal and cleaning of large (heavy) strainer baskets as well as for applications that might have varying solids loading conditions.  For example, automatic strainers are ideal for raw water intake pump suction strainers that might see higher particle loads after a rain storm.  Backwashing strainers are also used for remote locations where servicing simplex and duplex basket strainers would be difficult.

 

Although we can supply automatic strainers with mesh lined elements for retentions as fine as 75 microns, they are best suited for coarse retentions in the ¼" range and perhaps as fine as 100 mesh (150 microns). Due to the volume of process fluid used for cleaning, these strainers are almost exclusively used for water filtration; our standard materials of construction include cast iron, carbon steel and 316SS and for warm sea water applications we'll use an alloy like Hastelloy.

 

Principle of Operation

backwashing for automatic strainers

Filtration Mode
Flow enters the strainer body and must flow upwards into the strainer element, passing through it's perforated or mesh lined surface and exiting the vessel through the outlet nozzle.  The element is stationary and particulate that cannot pass through the element either falls to the bottom of the vessel or is lodged against the perforated or mesh lined surface of the element.

 

Backwash Mode
The backwashing cycle is actuated either by manual override, differential pressure or programmable timer.  Once it begins, simultaneously a draining valve opens and a motor atop of the strainer begins rotating a hollow shaft within the portion of the strainer that contains the filter element.  Attached to this hollow shaft is a vacuum nozzle which extends just above the inner surface of the filter element.

 

As this nozzle sweeps around the interior circumference of the filter element the resulting differential pressure (system pressure vs. atmospheric pressure) causes the clean, filtered fluid to revers flow through that section of the element, dislodging any material stuck to the inner surface of the element and its vacuumed through the hollow nozzle shaft, exiting the system via a backwash drain.

 

The motor has sufficient torque and the nozzle arm is designed to break-up debris such as sticks and other organic material that might accumulate onto the filter element surface.

 

Periodically it might be necessary to open the strainer body and remove large debris that may have settled to the bottom of the strainer; the straining element and backwash nozzle assembly is attached to the top section of the strainer, so it can be easily lifted for strainer element inspection and cleaning-out the bottom as needed.  We can also install a man way in the body to facilitate inspections and clean-out without having to disassemble the strainer.

 

Automatic Strainer Control Systems
Automatic strainers require a control package and we offer three basic versions, each of which can be further customized for all stainless steel wetted parts, explosion-proof components and optional control methods.

 

ACS-1 Control Package (base package): NEMA 4 panel box with adjustable timer, differential pressure override, 10 Amp control relay for backwash valve activation, "Power On”, “Backwash Cycle On”, “High Differential Pressure” indicator lights, selector switch to manually control the backwash valve and contact terminals for motor starter and external alarm. 120 Volt, 1 Phase, 60 Hz motor.

 

A single element differential pressure switch having aluminum wetted components activates the cleaning cycle. Dual element switches are available as an option to activate an additional alarm signal.

 

2” through 16” strainers, have electrically actuated standard port ball valves with a brass body, 316 SS ball & stem, TF seats and seals and threaded connections. 18” through 24” strainers have flanged  valves with a carbon steel body, ball & stem and TFE seats & seals. Electric actuators are NEMA 4 watertight enclosures operated from a signal from the control panel. Pneumatically actuated valves with NEMA 4 pilot solenoid are also available.

 

ACS-2 Control Package includes a motor starter in the NEMA 4 panel box in addition to the ACS-1 control package.

 

ACS-3 Control Package is for 460 Volt, 3 Phase, 60 Hz motors, includes a control voltage transformer and a motor starter in the NEMA 4 panel box in addition to the standard features of the ACS-1 package.

 

AUTOMATIC STRAINER FEATURES:
• Designed and constructed in accordance with ASME Section VIII, Division 1.
• ASME Code Stamp is available.
• Seismic qualification is also available.
• Unique quad shaft seal ensures that no process media leaks down the sides of the strainer.
• The motor, gear reducer, cover, and complete internal operating mechanism lift off as a unit, making all components easily accessible.
• Only a small portion of system flow is used during backwash due to the efficient hydraulic design.
• Zero Bypass of Contaminants because element caps are epoxy sealed to screen media.
• The cover O-ring permits resealing without time-consuming gasket replacements and adjustment.
• Manual override is a standard feature.

 

There are many variations and options that we do not show online, please fill-out our inquiry form for assistance.