Better separation is obtained by the thinner layers of liquid formed in the disc bowl centrifuge (Fig. 13.2). Here a cylindrical bowl, 0.2–1.2 m in diameter, contains a stack of inverted metal cones which have a fixed clearance of 0.5–1.27 mm and rotate at 2000–7000 rev/min. They have matching holes which form flow channels for liquid movement. Feed is introduced at the base of the disc stack and the denser fraction moves towards the wall of the bowl, along the underside of the discs. The lighter fraction is displaced towards the centre along the upper surfaces and both liquid streams are removed continuously by a weir system at the top of the centrifuge in a similar way to the tubular bowl system. Disc bowl centrifuges are used to separate cream from milk and to clarify oils, coffee extracts and juices. Disc bowl and tubular centrifuges have capacities of up to 150 000 l/h.