Polyethylene pipes are manufactured by a technique known as extrusion whereby material is continuously forced through a die to make finished products such as pipes. There are several parts to an extrusion line, all of which are vital to making high quality pipes:
The raw materials silo used to store the materials under ideal conditions before it is used in the extruder.
The supply system comprised of pipework and a vacuum system and used to transport the material from the silo to the extrusion line feed hopper.
The extruder comprised of an Archimedes screw rotating at a controlled speed inside a heated cylinder that heats the material to approximately 220°C and whose purpose is to:
- pick up the raw material and move it along the worm screw to the output;
- ‘plasticise’ and ‘melt’ it on its journey by heating it and mixing it between the screw and the cylinder;
- eventually ‘force’ it through a tool (die or punch),
The shaping tools used to calibrate the pipes and give them their definitive dimensions and shape before cooling them. This operation is done in a vacuum to maintain the pipe dimensions for as long as it takes for them to set through cooling.
The cooling trays used to remove the accumulated heat and ensure the material crystallises properly. This is very important as it endows the polyethylene pipes with all their mechanical properties.
The marking system used to mark the pipes with all the necessary product information such as diameter, thickness, etc. and traceability data such as the batch number, date of manufacture, etc. Three marking systems are currently in use: hot marking, inkjet marking and laser marking.
The puller, which is an essential piece of equipment as it sets the production speed of the extrusion line. The puller is synchronised with the extruder to ensure that the dimensional characteristics of the pipes remain constant during production.
The saw used to cut the pipes to the desired length and designed not to damage the pipes.
The pipe spooler used for packaging the pipes in coils or on drums. Cut lengths of pipe are deposited directly on pallets.
Thanks to materials that are constantly evolving and improving, extrusion is now able to produce polyethylene pipes of up to 2500 mm in diameter with thicknesses of up to 120 mm! It is also possible to coil several kilometres of pipe that can be laid in one go without any connections, providing fast, economical installation and optimum network security in terms of hermeticity.
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