Technological know-how for the extrusion of PP-R and PP-RCT pipes

29 March, 2023

PP-R (Random) and PP-RCT (Random Cristallinity Temperature) pipes, copolymers of polypropylene, have rapidly established themselves on the market in recent years due to their unique chemical and mechanical properties and the associated benefits in terms of performance and low environmental impact. Also, on demand in multilayer glass fibre configurations, PP-R pipes are increasingly being used in applications ranging from the domestic to the industrial sector: in the construction of hot and cold water distribution and water purification systems, in heating systems, in the transport of compressed air, but also for the transport of chemical fluids. In this sense, Bausano, with the aim of promptly responding to the growing demand of the various operators, enhances its expertise of more than 70 years with the development of extrusion lines dedicated to the production of this type of pipe.

Low thermal conductivity is the first distinguishing feature of PP-R pipes, guaranteeing increased insulation and, consequently, reduced heat loss or heat gain when transferring hot or cold fluids, respectively. The advantages are therefore high energy efficiency and lower insulation costs. A second factor is resistance, even under changing environmental conditions, in a temperature range of 20 to 95 °C, to abrasion by solid particles and to a wide range of liquids, including aggressive chemicals and alkaline solutions. As a result, PP-R pipes can maintain their functionality for more than 50 years in a variety of application situations. Furthermore, the low internal roughness ensures a lower coefficient of friction, further contributing to system efficiency. In the case of PP-R pipes in the multilayer configuration, the intermediate layer consists of a glass fibre compound, which further increases the pipe's strength and limits its thermal expansion. Lastly, these pipes are recognised for their healthiness, as they do not release toxic substances and are less prone to electrolysis, as well as being easy to install due to their light weight.

Each line, depending on the production required, consists of one or more single-screw extruders, equipped with a specially designed screw, which allows maximum performance in the PP-R pipe machining process, thanks to optimum melt plasticisation, combined with good dispersion when using masterbatch. Integrated into the line, the calibration and cooling benches, made of stainless steel, ensure effective cooling, aimed at reaching the pipe size, while providing a flawless surface. Completing the line are the drive system for a continuous, vibration-free drive, the cutting unit and the packaging wrapper, which gives the plant a very high degree of automation. The latter is, in fact, an automatic system, capable of forming bundles of pipes of the predetermined number, from 16 to 125 mm in diameter and from 1 m to 6 m in length. Finally, thanks to Digital Extruder Control 4.0 on board the machine it is possible to constantly monitor the system, to control the different stages and analyse the collected data for higher efficiency.

Regarding the feeding system used, the presence of an advanced and extremely precise technology, such as the gravimetric dosing unit, brings considerable advantages, as it is a prerequisite for constant production, aimed at reducing overweight, while maintaining the diameter and thickness dimensions in accordance with the reference standards. In particular, this system is based on a load cell capable of measuring the weight of the material processed by the extruder in real time, sending continuous feedback to the Digital Extruder Control 4.0 (PLC), which calculates and determines the rotation speed of the extruder screw, depending on the mass detected. In turn, the extrusion speed is adapted according to this parameter while keeping the weight/metre of the pipe constant, a decisive feature in the event of any variations upstream in the machining process. In this way, Bausano lines allow each metre of pipe to be extruded to predefined specifications.

"The combination of superior performance and lower raw material costs is leading to the increasing use of PP-R pipes, replacing the less efficient metal pipes," said Massimiliano Fenili, Bausano's Technical Manager. "For this reason, at Bausano we have been specialising for some time in the design of dedicated extrusion lines that can meet the most challenging requirements of our customers. The goal we constantly keep in mind is in fact to offer a complete solution, aimed at guaranteeing maximum results and designed down to the smallest detail to optimally process the chosen material, with particular regard to its rheological behaviour. The inclusion of the gravimetric dosing unit, which provides interesting data on the amount of plastic processed, combined with downstream automation such as the bar wrapper, testifies to our commitment to customising our technology to specific production requirements.”