Polyamide 12 for High Pressure Gas Installations [polyamide]

PA 12 is a high performance polymer with outstanding mechanical properties and excellent chemical stability. It is the preferred material in many demanding applications, e. g. in the automotive industry for fuel lines of passenger cars or for air brake tubing in trucks. Compared with polyethylene (HDPE) it has a higher mechanical and impact strength and melting temperature. That is why it can withstand higher pressures and temperatures. It also has much lower gas permeability and is easy to be processed in extrusion and injection molding. For more than 20 years PA 12 is evaluated as a pipe material for gas distribution and for more than 10 years PA 12 pipes have been used in Australia, Poland and Chile for low pressure installations. In recent years PA 12 is being investigated for operation pressures above 10 bar. Since 2002 a working group within the ISO/TC 138 is elaborating standards for PA 12 gas installation systems with operation pressures up to 20 bar (2MPa, 290 psig). In USA the ASTM F17 committee is working on the standardization of PA 12 for gas installation and the Gas Technology Institute (GTI) has set up a comprehensive test program for a feasibility study of PA 12 gas pipes with diameters up to 6” (168 mm OD, SDR-11). This program is sponsored by 15 major gas utilities in USA and will last 27 months including some test installations in various states which are scheduled for the beginning of 2006. Degussa AG, Marl, Germany, as one of the four manufacturers of PA 12 and E.ON Ruhrgas are cooperating on a first test installation of a 60 m pipe system (110 mm OD, SDR-11) in the technical center of E.ON Ruhrgas in Dorsten, Germany. The system with two butt fusion, two electro-fusion joints, and electro-fusion end caps was checked 72 hours at 36 bars (3.6 MPa, 520 psig) and is operating now for 2 years at 24 bar (2.4 MPa, 347 psig). The authors will give an introduction to the excellent technical performance of PA 12 and demonstrate the superior cost position of high pressure PA 12 gas pipes with respect to steel. PA 12 is technically and economically the material of choice for gas distribution at 10 - 20 bar (1 -2 MPa, 145 - 290 psig).