Copa®  Raked Bar Screen

The Copa® Raked Bar Screen is ideally suited to both new and existing Combined Sewer Overflow (CSO) chambers where high frequency spills can be expected. Its modular design is ideal for retro-fit installations (requiring little or no civil work to the existing CSO chamber) and allows the unit to be assembled below ground through just a 600mm diameter manhole.

Flow rates from 50 – 3000 litres / second can be catered for by a single screen, although multiple units may be used to increase flow capacity

4mm, 6mm and 10mm bar screening are available and suitable for high volume and frequent spill CSO’ works.

Screen modules are mounted horizontally along the storm discharge weir (making the system ideal for single-sided and double-sided weir installations). Screen bars are set to the same level as the overflow weir. An ultrasonic control system monitors the upstream water level and signals the screen to start before the water flows upward through the bars. The combs move back and forth on a continuous basis to keep the screen face clear. Screenings are prevented from passing over the weir and are retained in the foul sewer for transportation to treatment. Once the water level drops below the overflow weir level, the sensor will signal the screen to stop after a ‘run on’ period, ensuring that the screen is clear for the next overflow event.

All screens are operated remotely by a 1.1kw motor hydraulic power pack, which may be located up to 100m from the CSO chamber. Hydraulic connection is by 3/8” hydraulic hose. Longer distances between the screen and power pack can be achieved by increasing the hydraulic hose to ½” and / or increasing the size of the hydraulic power pack.

Our extensive research into CSO screens concludes that horizontal screens are far more efficient than their vertical counterparts. In a vertical configuration, only the bottom section of the screen is used during periods of low flow, and flow velocity is significantly higher which can force debris through the bars. With a horizontal configuration the entire screen is used, no matter how high or low the flow.

Flow velocity is kept to a minimum and the need for secondary weirs is eliminated, thus preventing grit and heavy solids from becoming trapped and so reducing the screen’s efficiency. It is possible to walk on top of the horizontal screen’s bars, making access to the installation simpler and more convenient.

The Copa® Raked Bar Screen has few maintenance requirements and all maintenance may be carried out from the top / clean water side of the screen. Both the guide rods and comb drive unit are easily removed for inspection or replacement. It is not necessary to remove the main framework or screening bars for normal maintenance, but should this be required, each module may be split from its partners and removed individually. Vegetable based hydraulic fluid may be changed from within the remote control kiosk, eliminating the need to enter any confined spaces around the screen. Oil changes are required on an annual basis. Periodic visual inspections are recommended to ensure that there is no fouling or damage caused by debris during extreme storm conditions.