Abstract: A separator includes a housing, a basket rotatably mounted in the housing and a movable weir member. The basket has an upstream end portion, a downstream end portion and an intermediate tubular portion that includes or forms a screen deck. The weir member is movable between a first position where a portion of the weir member extends radially inward relative to the inner surface of the downstream open end portion and a second position spaced from the first position. In this manner, the weir member forms a movable dam adjacent the downstream end portion of the basket. In operation, feed material is fed into the basket as the basket is rotated. The heavy fractions of the material pass transversely through the basket (i.e., the tubular portion that forms a screen deck) and report to a first outlet from which the heavy fractions are collected.