System Experience & Training # 1998 Gothenburg
In the Netherlands, rigid PVC and impact-modified PVC pipes have been used in gas distribution systems for dozens of years. In general, these pipes have performed excellently. Some years ago, however. questions were raised about the resistance of these materials to certain gas constituents. An extensive research programme was then started to investigate these problems.The results of this research programme are reported in this paper and are of value to other pipe applications as well. Crazing and cracking in various gaseous environments and in natural gas condensate have been examined in many long-term studies. Long-term failure in PVC pipe systems is always preceded by crazing. Crazing and cracking are strongly affected by the various gaseous environments. However, below certain concentrations, which are representative of the commonly distributed natural gases, higher hydrocarbons have no detrimental effect on PVC pipe materials. Natural gas condensate only affects PVC under extreme conditions which hardly ever occur. It was proven once again that (impact-modified) PVC is an excellent pipe material for low-pressure gas distribution systems.