Tubular Backwashing Filters

This article describes our automatic tubular backwashing filtration systems for particle retentions as fine as 2 microns. While both the 2596 and tubular backwashing designs rely on system differential pressure to backwash the filter element, the tubular backwashing design can retain much finer particles and is a scalable design to enable fine filtration of high flow rates.

Benefits and Applications

Finer retention capability means that these systems typically replace bag filter and filter cartridge systems which are applied to the 2 to 1,000 micron range.

• Cost Savings: When compared with disposable media systems, tubular backwashing filtration systems reduce costs associated with labor and downtime by reducing replacement, handling, and disposal of disposable media.
• Eco-Friendly: The "cleaned-in place" tubular backwashing filter design supports an environmentally conscious approach to waste reduction.
• High Pressure Operation: Designed for operation at pressures up to 1,000 PSIG.
• Typical Uses: Used mostly for industrial water applications, hot condensate, chiller water, paper mill "white water", clean-in-place water, and a wide variety of automated processes.
• Process Protection: Ideal for systems requiring a stable pressure or a fine level of filtration to protect the equipment and processes downstream of the filter system.

How Tubular Backwashing Filters Work

1. Filtration: Unfiltered liquid enters the filter station, passing through the sealed filter element. Particles that are too large either accumulate on the element surface or fall to the bottom of the vessel chamber.
2. Actuation: Backwashing of the element occurs when the 3-way inlet valve actuates, closing-off the inlet and opening the drain port. The actuation can be performed manually for single station systems and can be automatically actuated (pneumatically or electrically) using a programmable timer or differential pressure switch.
3. Cleaning: The backpressure of the system causes the flow to reverse through the element, using the already filtered liquid to backwash through the element and flush the vessel clean. A system pressure of 45 PSIG is required for efficient cleaning.
4. Efficiency: The time required for this process is typically only a few seconds per filter station and uses <2% of the flow rate.

System Configurations: AFC Matrix vs. AFR Compact

Most tubular filtration systems consist of multiple filter stations installed in parallel. Once backwashing is initiated, each filter station undergoes the cycle in series to ensure sufficient flow and minimal pressure loss during the backwashing cycle.

• Matrix Expansion: Tubular backwashing filter systems can have as many as 14 filter stations, with each station supporting up to 150 GPM. They can be provided with "blank stations"—capped connections on extended manifolds to enable additional filter stations to be added at a later date.
• Flexible Footprints: The design is not constrained to a linear 1 x 14 arrangement. They can be arranged in a 2 x 7 matrix, reducing the filtration system length by 50% and only slightly increasing its width.
• External Backwash Option: A separate liquid source for backwashing can be accommodated by adding a 4th manifold and a 2nd set of control valves. This is required when the filtered liquid is too valuable or hazardous, the system pressure is <45 PSIG, or the process cannot tolerate slight flow rate fluctuations.

Filter Element Design

The requirements of your application will determine the design of the internal element, which is offered in 1, 3, and 7 chamber designs. All three designs have a single seal and are physically one unit, however, additional chambers increase the total surface area and therefore increase the open area ratio for a given size filter station.

Depending upon the liquid viscosity and other factors, incorporating backwashing flow diffusers is an option to maximize backwashing efficiency and minimize backwashing cycle time.