Ductile Iron pipe is manufactured by a metallurgical process which involves the addition of a magnesium alloy into molten iron, giving a graphite structure which is nodular. The pipe is centrifugally cast in water cooled metal moulds. Casting is followed by heat treatment in a continuous annealing oven, after which the pipe passes through the various finishing operations. These include hydrostatic testing, cleaning, cement lining, coating and inspection. Rigid process and quality control is exercised throughout the manufacturing cycle.