Band Screens

With these fine screens the screenings capture isn’t that good and the constant maintenance can be a nightmare, thus, the band screen appears to be unit that has really pushed out ahead of the other fine screens.

Thin perforate plates (typically 2 mm or 1/16” thick [metric system conversion]) attached to a roller chain drive, upper and lower sprockets, frame, motor and gear reduction make up the continuous band screen. The perforated plate, which is the signature of the band screen, captures naissance fibrous materials such as cotton balls, rags, and body hair.

Capturing these materials at the band screens is essential for successful operation some of these advance treatment process, but it also comes with undesirable consequences. The small opening on the band screen does such an awesome job removing the materials that the band screen often becomes blinded by hair pinning and rag stapling.

To remove these materials from the band screen requires a significant effort, pressurized water jets or vigorous rotating brushing is needed, and frequently. Some band screens experience this problem and it has been a set back for those particular brand screens, but some band screen manufacturers have patented designs that have been successful with combating the issue of hair pinning.

In addition to being used at the headworks of treatment plants, the band screen is also used at combined sewer outfalls and in storm sewers for greater removal efficiency. Band screens can be installed in sumps/wells that range in depth from 1 m to 15 m or (3.3 ft to 49 ft), and channels widths from 0.7 m to 1.5 m or (2.3 ft or 5 ft).

The flow pattern of the band screen follows a center feed type design that directs the flow through the perforated screen plate that is parallel to the flow of the channel. Once through the screen, screenings are captured by screening elements, and the screened flow takes a 90 degree turn out the side of the unit continuing in the direction guided by the channel arrangement.

The screenings that are captured are lifted out of the channel and then cleaned with either brush or pressurized spray nozzles. Debris should be thoroughly cleaned from the perforated plates to minimized carry-over into the downstream side of the band screen as the perforated plate re-enters the channel flow. Captured solids are collecting in a storage container or hopper where it will remain until it can be disposed of.