b'LT ENGINEERINGCATALOGScreening Device ClassificationSCREENING DEVICE CLASSIFICATION SIZE CLASSIFICATION / SIZE RANGE OF SCREEN OPENINGBAR SCREENMANUALLY CLEANED COARSE / 25-50 MM (1-2 IN)MECHANICALLY CLEANED COARSE / 15-75 MM (0.6-3.0 IN)FINE BAR OR PERFORATED COARSE SCREEN (MECHANICALLY CLEANED)FINE BAR FINE COARSE / 3-12.5 MM (0.1-0.5 IN)PERFORATED PLATE FINE COARSE / 3-9.5 MM (0.1-0.4 IN)ROTARY DRUM FINE COARSE / 3-12.5 MM (0.1-0.5 IN)FINE SCREEN (MECHANICALLY CLEANED) Wastewater SystemsFIXED PARABOLIC FINE / 0.25-3.2 MM (0.01-0.13 IN)ROTARY DRUM FINE / 0.25-3.2 MM (0.01-0.13 IN)ROTARY DISK VERY FINE (MICRO) / 0.15-0.38 MM (0.01-0.02) SIZING MAINTENANCEParkUSA offers full support on designing a Bar ScreenManually cleaned screens require frequent raking to prevent System. The variations present when designing a Bar Screenclogging. Cleaning frequency depends on the characteristics System tend to make difficult to standardize a model. of the wastewater entering a plant. Some plants have Many variables have direct effect on the final model, incorporated screening devices, such as basket-type trash such as space availability, rainfall intensity, sediments load,racks, that are manually hoisted and cleaned. Mechanically trash types, BOD/COD presence, etc.cleaned screens usually require less labor for operation than manually cleaned screens because screenings are raked The quantity of screenings depends on the length andwith a mechanical device rather than by facility personnel. slope of the collection system and the presence of pumpingHowever, the rake teeth on mechanically cleaned screens stations. When the collection system is long and steep ormust be routinely inspected because of their susceptibility when pumping stations exist, fewer screenings are producedto breakage and bending. Drive mechanisms must also be because of disintegration of solids. Other factors thatfrequently inspected to prevent fouling due to grit and rags. affect screening quantities are related to flow, as quantitiesGrit removed from screens must be disposed of regularly.generally increase greatly during storm flows. Peak daily removals may vary by a 20:1 ratio on an hourly basis from average flow conditions. Combined collection systems may produce several times the coarse screenings produced by separate collection systems.Given the complexity of collection systems and types of materials that may be considered grit, the quantity and characteristics of grit removed from wastewater will vary. Grit quantity is influenced by the type and condition of the collection system, the characteristics of the drainage area, garbage disposal methods, the slope of the collection system, and the efficiency of the grit removal system.INFO@PARKUSA.COM|888-611-7275|WWW.PARKUSA.COM 431'