Читать книгу Automation of Water Resource Recovery Facilities - Water Environment Federation - Страница 233

Bar screens stop material that is too large to fit through bar openings. Facilities typically have a number of bar screens in parallel. More than one bar screen is typically needed so that availability is maintained during maintenance. In addition, optimal velocity through the bar screen should be maintained between 0.4 and 0.9 m/s (1.25 to 3.0 ft/sec). This prevents grit settling in the chamber at low velocity and material being pushed through the screen at high velocity.

Many bar screens have rakes that can operate intermittently. The rake must operate frequently enough to ensure that material does not build up on the rack and blind it; however, if the rake operates too frequently, it will increase wear on the equipment, which will increase the frequency of maintenance and likely reduce its availability.