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PBEI | March 2017 9 A gyratory sifter (also called a screener, classifier, or separa- tor) consists of a stack of multiple square, rectangular, or round screen decks, as shown in Figure 1. The screen decks are mounted on a stationary base that's equipped with a drive mechanism. This article concentrates on gravity-fed sifters, which have square or rectangular screen decks. [Editor's note: Sifters with round screens decks are typically fed under pressure rather than by gravity, a topic outside the scope of this article; however, many of the same maintenance princi- ples discussed here also apply to sifters with round screen decks. For more information, see "For further reading" later in this article.] Each screen deck consists of a heavy-duty frame that typ- ically holds a pretensioned screen insert (also called a screen panel), as shown in Figure 2a. The screen insert consists of a screen cloth that's stretched and attached to a lightweight frame, as shown in Figure 2b, to simplify the screen's inser- tion into the screen deck frame. (In some gyratory sifters, the screen cloth is stretched and fastened directly to the screen deck frame.) The screen insert may also include a carrier wire of coarse mesh mounted below the screen for holding a set of screen cleaners, such as plastic balls or cubes. A top cover with a material inlet is mounted on the top screen deck. In operation, the sifter's drive mechanism — consisting of eccentric weights powered by an electric motor — imparts a low-frequency, high-amplitude gyratory motion to the screen decks, causing them to move in a gentle circular motion in a horizontal plane. After entering the inlet in the sifter's top cover, the material is immediately stratified by the gyratory motion. Fines are in contact with the first screen and begin to pass through. The fines that don't pass through the first screen flow along with the oversize onto the next screen. If a screen in- sert has screen cleaners, they bounce against the screen bottom, helping prevent near-size or sticky particles from clogging the After describing the gyratory sifter's operation and proper installation, this article outlines monthly and yearly maintenance steps that will keep the unit's screen decks in peak condition. Screen deck maintenance for your gyrating sier Mantenimiento de los filtros en cribadores giratorios Después de describir el funcionamiento y la correcta instalación de un cribador giratorio, el siguiente artículo hace hincapié en los pasos que deben darse mensual y anualmente para mantener los filtros de los cribadores en perfectas condiciones. présente l'entretien mensuel et annuel à réaliser afin de maintenir les étages de tamisage en état optimal. Entretenir l'étage de tamisage de votre tamiseur giratoire Cet article décrit d'abord le fonctionnement et la bonne installation du tamiseur giratoire, puis Wartung eines kreisförmig schwingenden Siebs Nachdem der Betrieb eines kreisförmig schwingenden Siebs, und auch die richtige Installation des Siebs beschrieben wurde, erläutert dieser Artikel die Stufen die zur monatlichen und jährlichen Wartung notwendig sind, um die Siebdecks des Gerätes in einer Spitzenkondition zu halten. Derek J. Williams Sifter Parts & Service