TPT July 2007

P lastic & C omposite T ube: P roducts & M anufacture

There was a time, and not so very long ago, when the word ‘plastic’ did not appear in a publication such as Tube & Pipe Technology . Old-timers will recall an early problem with the dubious new material: was the preferred adjective ‘plastic’ or ‘plastics’? It seemed unlikely that the subject of such effete reflections would find a place in an industry with its roots in iron and steel. Moreover, the new technology was promising the moon. Makers of tube and pipe know how to greet large claims for untested new products: with profound skepticism.

But the proof was not long in coming, and it was solid. Applications incorporating the new plastics enabled tube and pipe producers to promise value- added performance. These producers were also able to deliver efficient heat exchange characteristics, cross-contamination resistance, robustness to a wide range of chemicals and temperatures from -40¼ºC to 120¼ºC, and much more. The inert nature of PVDF, PP, and HDPE thermoplastics ushered the producers to places – particularly in the chemical, pharmaceutical, and electronics industries – well outside their traditional territory. In fact, the use of plastics and composites in tube and pipe manufacture has come very close to giving them the moon.

Today, there are no sceptics in the industry.

Testing of plastic-metal multilayer pipe systems

Consisting of plastic and metal, multilayer pipe systems offer advantages of high resistance to internal pressure (especially at high temperatures), innovative and economical fitting technologies and easy mounting. In general, multilayer pipes and fittings of different systems cannot be interchanged due to the large number of design varieties. Therefore it is important to test pipe and fitting systems very thoroughly before installation, especially as metal and plastic have different thermal coefficients of expansion. If the temperature differs substantially, as for example in drinking water installations, tightness and durability of these systems can be crucial properties. SKZ is an accredited institute for testing according to DIN EN ISO/IEC 17025 and an accredited inspection body according to DIN EN ISO/IEC 17020.

assurance of pipe systems meeting national and international specifications.

SKZ operates as a testing laboratory and inspection body for systems used in drinking water installation on behalf of DVGW in Bonn, Germany. In the field of floor heating systems SKZ cooperates with the certifier DIN Certo of Berlin, Germany. In addition, SKZ is its own certifier for products marked with the reputable SKZ-sign. Typical tests on multilayer pipe systems executed by SKZ are long-term hydrostatic pressure tests at different temperatures, together with dip thermal cycling tests. Here adhesion from plastic medium pipe and aluminium pipe is tested after a long- term thermal cyclic load. Within 15 minutes, the pipe is loaded with cold water at 20°C and with hot water at 93°C at 10 bar internal pressure. This cycle is repeated 5,000 times, which takes about 105 days. Following this process, the minimum adhesive strength is tested

› Aluminium layer peeled off plastic medium pipe

during a so-called separation test (see picture above).

Süddeutsches Kunststoff-Zentrum (SKZ) – Germany

Fax : +49 931 4104 277 Email : j.wuest@skz.de Website : www.skz.de

The company provides mechanical testing devices required for certification and quality

86

J uly /A ugust 2007