Issue link: http://www.e-digitaleditions.com/i/796485
10 March 2017 | PBEI screen openings. On-size particles flow through all the screens and discharge through the sifter outlet. The gyratory sifter's screens are subject to a lot of me- chanical stress and wear from the sifter's high-amplitude motion. This can enlarge the screen holes, resulting in off- spec final product, and eventually tear or otherwise damage the screen. Regularly inspecting, cleaning, and, when neces- sary, replacing the screen decks is the best way to keep your sifter performing as it should. But before we talk about screen deck maintenance, let's explore an important preliminary step in minimizing re- quired maintenance: correctly installing the sifter. Properly installing the sifter Before installing your gyratory sifter, be aware that the manufacturer dynamically balanced the sifter's drive mecha- nism for your application before the sifter left the factory. This ensures that the sifter will gyrate correctly for maxi- mum screening efficiency in your process. Once the sifter ar- rives at your plant, don't try to change the drive mechanism's balance, because even a slight imbalance can cause harmful vibra- tions and reduce the sifter's efficiency. Using the installation drawing supplied by the manu- facturer, install the sifter by following these basic steps: Choose a location with ample clearance. Make sure that you choose a spot for the sifter that allows ample clearance between it and any connecting spouts, hoppers, and convey- ors so they can't impede the sifter's operation. The clearance should also keep the sifter's moving parts from contacting any stationary equipment or structures and allow easy access for changing the sifter's mechanical parts and screens. Level the base. Install the sifter's stationary base, ensur- ing that it's perfectly level before mounting the sifter on it. A level base is crucial for maintaining the sifter's balance so it can achieve maximum screening capacity and efficiency. Properly position the sifter on the base. Using a sling or similar device on a forklift or hoist, gently lower the sifter until one (or more) of its mounting feet just touches the base. Use a carpenter's level to ensure that the sifter is level, and then place shims under the mounting feet that aren't yet touching the base. When all the mounting feet are solidly on the base, check the level again and, when the sifter is level, bolt the sifter onto the base through the base and feet bolt holes. If the base and mounting feet bolt holes don't line up, don't force the mounting feet out of position; instead, relocate or enlarge the base holes to align with the feet holes. Carefully attach flexible inlet and outlet connections. Use flexible tubes to connect the sifter's inlet and outlet to upstream and downstream equipment, but don't stretch the tubes so much that they become taut and can restrict the sift- er's gyration. Secure both ends of each tube with the clamps provided with your sifter. Properly install the sifter's external wiring. Use the wir- ing diagrams supplied by the sifter manufacturer to install the wiring from the sifter to the motor and motor starter. Ensure that the installed wiring conforms to local electrical standards. Figure 1 Gyratory sifter Figure 2 Screen insert Inlet Hold-down rods Screen decks Motor Drive mechanism Outlet a. Typical screen insert b. Attaching screen to insert frame