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AFC Tubular Backwashing Filters

The AFC style tubular backwashing filter is applicable to applications for pressures up to 1000 PSI and for retention continuous removal of particles as fine as 1 micron.  Individual filter stations are capable of 60 GPM and can be multiplexed to handle nearly 6,000 flow rates.

Principle of Operation

During filtering mode, flow enters the bottom of the filter station, passing through the filter element wall and through the outlet of the vessel.  Particulate too large to pass through the element either falls to the bottom of the filter vessel or is sucked against the side of the element.

 

During backwashing mode a 3-way valve cycles, closing the inlet for a few seconds and opening to the drain port, thus the system pressure reverses flow through the element; the filtered fluid passes through the element dislodging accumulated particulate from the filter element openings and they flushed out through the drain port.


Single filter stations can be controlled manually or automated.  Multiple station systems typically use automated valves and once backwashing mode begins, each filter station undergoes the backwashing process until all have been backwashed.


Backwashing is initiated either via manual override, programmable timer or differential pressure.  The system needs to be sized such that there's sufficient filtration area available during backwashing and the process flow needs to accommodate not only the flow required for the process but the slightly additional flow required for backwashing.  If the system consists of only a few filter stations the backwash volume and time is negligible but it might be a consideration for larger systems.


INTERNAL EXTERNAL
Low Viscosity Viscous Liquids
Low Value High Value
>45 PSI <45 PSI
Fluctuations are okay Fluctuations are not okay
Internal or External Backwashing?
Internal backwashing uses <2% of the filtered process fluid to reverse flow through the cartridge and flush contaminates from the system.  The process fluid has to be "low value", meaning it's okay to "waste" some for filter element cleaning.  The process fluid also has to have a low viscosity otherwise the cleaning process isn't as efficient.  Operating pressure is another concern, it has to be at least 45 PSI to maintain cleaning efficiencies.

External backwashing simply means that the fluid flowing in the "reversed" direction comes from elsewhere than the process fluid.  For some applications this may be necessary, such when there's a chemistry aspect to cleaning the element.  External flushing is also required for viscous fluid applications, when the process fluid is "valuable" and for systems that have operating pressure <45 PSI.

It should be noted that internal backwashing systems result in slight fluctuations in process system flow, whereas external backwashed systems are required with the process cannot tolerate flow fluctuations.

Features:

• Smooth pipe transitions minimize pressure drop.
• Many backwash options to support operator-free service.
• < 2% of system volume required for backwashing.
• Quick coupler valve connectors simplify body tube removal.


Options:

• Single, double and multiplex configurations to handle high flow rates.
• Internal and external backwashing configurations.


Limitations:

• 100 to 150 ppm particle concentration.

• 12 FPS flow velocity.


For backwashing:

• Requires 45 PSI for internal backwashing.

• Clean backwash source for external backwashing.

• Some fabric covered elements require backwashing pressure <50 PSI.


What is the Maximum Flow per Element?

This is not a straight-forward answer, we have to calculate the maximum flow per element based upon our basic design standards of < 3-5 PSI differential pressure and maximum of 15 PSI differential pressure when cleaning is needed.  We require the following information from you to properly size the filter element:

 

1. Flow rate in GPM (gallons per minute)
2. The retention size required
3. Viscosity of the fluid
4. Is it a continuous or batch application?

 

These characteristics and others are included on our online inquiry form, please fill it out as much as applicable so that we can begin to assist you with the proper selection and sizing of a filter system.

 

Approximate sizing chart

Maximum Flow Rate Model Type
60 GPM 1100S Simplex
1100D Duplex
480 GPM 1100-IB Internal Backwashing
1100-EB External Backwashing
150 GPM 1500S Simplex
1500D Duplex
450 GPM 2200S Simplex
2200D Duplex
3,500 GPM 2200-IB Internal Backwashing
2200-EB External Backwashing
5,880 GPM 3300S Simplex
3300D Duplex
3300-IB Internal Backwashing