The manufacturing process
First, iron is melted in the cupola furnace at approx. 1,550 °C using scrap steel and recycled materials. In order to obtain ductile cast iron, the iron is injected in the converter with a magnesium alloy.Pipes are then manufactured from the “injected” iron using the centrifugal casting process.
The pipes which leave the centrifugal casting shop are annealed at 960 °C in a continuous furnace, so that the cementite can be broken down into ferrite and graphite.
All pipes are then given a zinc or zinc-aluminium casing, cleaned in the sleeve area, spray-galvanised and pressure-tested at up to 50 bar, followed by a visual, dimensional and material check.
The pipes are now processed further for their later application. Fresh water pipes are given a cement mortar lining on the basis of blast-furnace cement, and waste water pipes a cement lining based on alumina cement.
The lining, a mixture of sand, cement and water, is applied using the latest centrifugal machines. This has the advantage of a very high compression level of the cement mortar lining, and thus increased resistance to abrasion. The cement mortar linings are then allowed to set in maturing chambers at a defined air humidity and temperature.
The pipes then receive their outer coating. Some of the pipes are painted – fresh water pipes with a blue epoxy resin paint and waste water pipes in brown. After the drying time and spraying with water, the pipes are then marked with their production date and standard.