Tube extrusion lines - Fabrication steps

Pipes have long been used to transport fluids.

The advent of plastics has made it possible to produce pipes whose mechanical characteristics (Young's modulus or stress at rupture) are admittedly lower than those of cast iron or concrete, but their viscoplastic nature (creep) means that, under constant deformation, the stress decreases over time, or even disappears. This characteristic is very important for drainage and distribution pipes (used in urban networks), which are buried and undergo significant deformation due to burial. Their resistance to the internal pressure of the fluid is therefore not reduced if they are deformed, unlike steel or cast-iron pipes, which undergo brittle fracture if deformed too much. The use of high-temperature-resistant polymers has extended the use of polymer materials to the distribution of hot water in the home, for sanitary or heating purposes. The flexibility, ease of processing and chemical neutrality of plastics are also useful in the production of catheters for the medical sector. Finally, this flexibility, combined with the mechanical strength of a braided metal reinforcement, enables the manufacture of high-pressure-resistant technical pipes (hydraulic hoses and oil rig umbilicals).

This explains why more than half the world's pipes (59%) are currently made of thermoplastics, and why their annual growth over the period 2002-2006 was 4.8% (compared with 3.1% for other materials, see [Doc. AM 3 643] ).

All these pipes are manufactured by extrusion (single-screw or twin-screw), a process for producing parts with a constant cross-section. Whatever the extruder, its function is to plasticize the material in order to push it into the extrusion (or forming) head. For further information, please refer to the :

• "Extrusion – Single-screw extrusion [AM 3 650] and [AM 3 651] ;

• "Extrusion – Bivariate extrusion processes"