Travelling Band Screens

Travelling Band Screens (TBS) are used where large volumes of water must be screened to remove floating and suspended material, which might damage downstream pumps and equipment. The screen mesh is attached to basket frames arranged in an endless link chain system. As the water flows through the baskets, debris is retained within the baskets, allowing the clean water to flow through the screens. The trapped screenings are carried over to the top by the revolving band screen where jets of water discharge the debris into a refuse trench for disposal. The spray header pipe is fitted with highly efficient spray nozzles to effectively backwash the screening baskets. The spray header pipe can also be fitted with an internal cleaning device for cleaning the spray nozzles.Macmet designs and supplies Revolving travelling band with sealed drive unit and automatic basket cleaning operation with mesh sizes 100 micron. Three types of TBS with different flow patterns are available for removal of solids from water.Through-Flow Band Screen: Designed for water flow through the screens and discharging retained solids into a refuse trench. 50% effective submerged mesh area. Mesh sizes from 4 to 10 mm.Dual-Flow Band Screen: Designed for water flow from outside to inside of the screens and discharging retained solids into a refuse trench. 100% effective submerged mesh area. Mesh sizes from 4 to 10 mm.Centre-Flow Band Screen: Designed for water flow from inside to outside of the scrfeens and discharging retained solids into an internal collecting trough. 150% effective submerged mesh area due to basket configuration. Mesh sizes from 0.1 to 10 mm.The flow pattern across the screen in case of Dual flow and Centre-flow TBS eliminates any possibility of carrying over of collected trash to the downstream side.When compared to Through-flow type TBS, the Dual-flow and Centre-flow TBS provides an increase in screening capacity by approximately 50% and 100% respectively. The Centre-flow type TBS with its unique semi-circular basket design provides much higher trash removal capacity compared to flat basket design in other two types of TBS. The semi-circular baskets are equipped with a retaining plate, which provides bucket elevator type characteristics to carry bulky debris without any fallout. Also, as the debris is discharged by gravity, less wash water is required for back-washing the screens. The mesh size is selected to obtain the quality of water required for individual applications. Fine mesh openings are most effective for removal of tiny particles and jelly fish. Common sizes of mesh opening for power utilities and desalination stations are 1 mm to 2 mm. This guarantees high quality water and eliminates the requirement of further downstream filtration equipment particularly at condenser inlet. C entre-flow type TBS can be designed for flow rates up to 100,000 m3/hr with optimum debris removal because of its high screening capacity. One of the most important features of a Centre-flow TBS is the reduced civil construction on account of the possible higher sump level. Compared to Centre-flow screens, the civil structures for Dual-flow and Through-flow screens are higher by 30% and 50% respectively.