# 2001 Munich
This presentation illustrates the extended functional possibilities yielded by multilayer systems based on simple polyethylene pipes installed underground. A simple, installed polyethylene pipe comprises:
• A core, through which the medium to be transported flows,
• A pipe wall made of polyethylene, which is equipped with colorant, UV-stabiliser and antioxidants and which serves to separate the medium from the surrounding area, while simultaneously withstanding the pressure of both the medium itself and the ambient pressure of the surrounding soil,
• The surrounding soil in which the pipe is installed.
Today, pipelines such as this are employed in the field of water supply in sizes ranging from approx. 10 to 1600 mm, with wall thicknesses between 0.5 and 100 mm, and can be delivered in lengths of up to several kilometres (Figure 1).
Plastic pipes are produced as endless strands on extrusion systems.
The manufacturing facility must be designed specifically for the special pipe structure (Figure 2). In order to be able to better classify multilayer systems, let us assume the following layer structure. Not every multilayer system will have all of these individual layers. Indeed, one layer may also have several tasks at the same time.