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.
Four centrifugal casting machines ensure that Buderus produces up to 2,500 pipes of different nominal widths every day.
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.
Yet other pipes are given a special plastic-modified cement mortar coating. These pipes can then be installed in particularly aggressive and stony soils. Again for identification purposes, the cement mortar coating is coloured – the fresh water pipes blue and the waste water pipes brown.
After a thorough final check, all the pipes are then placed in the pipe store to await transport to the point of installation.
