An 800 metre-long channel of moving water has replaced a 3264 square metre still-water artificial lake, in a plant used to cast blocks of bitumous roofing material. The newly cast floating moulds cool and solidify as they are conveyed along the channel to de-moulding and palletising equipment. The emptied moulds are then returned to the casting head. The resulting continuous production casting line is fully automatic, and operates without any process personnel. To fit the new flume into a 400 square metre footprint, it was necessary to include 5 hairpin bends, which the floating moulds could not round without assistance. The problem was overcome by adding submerged revolving discs that lift the moulds and carry them around the bends. Because of the continuous unmanned operation of the plant, the design of the disc and drive bearings had to be 100% reliable for use underwater, with a predictable, planned maintenance requirement.The use of a friction drive on the outer edge of the disc imposes a side loading on the central disc bearing, which would eventually wear the HPDE disc. To overcome this, the central hole is lined with an iglidur® X flange bearing, which can be replaced at regular intervals, before wear becomes a problem. The weight of the disc (negligible underwater) is carried on an iglidur ® X thrust washer, with a further thrust washer below the head of the 12mm stainless steel shoulder bolt pivot. Finally, the stainless steel shaft for the edge friction drive passes through two igubal® rod-end bearings.