Gustaaf SUYS, MA ZHOU, Dave CORDEROY
Case Studies from Around the World # 2004 Milan
A sector of the Beijing Natural Gas Company network was to be converted from town gas to natural gas. It was found that the existing steel pipeline installed in 1983 could not withstand the working pressure, as parts of the steel pipes were seriously corroded. The system consisted of about 2.7 and 0.2 km of respectively 700 mm and 500 mm steel pipes, operating at relatively low pressure. The need for rehabilitation was clear and it was decided that insertion of a PE100 pipe of 315 mm SDR11 operating at 10 bar, would bring an optimal technical and economical solution. As, since 1983, great changes have taken place in the reference buildings above ground and pipe systems underground, the preparation work included extensive redefinition of the relative position with other pipes. Also additional work of investigation on pipe data, landscaping, traffic, site inspections… was required. The choice of PE100 for the new pipe line in conformity to the GB 15558.1 was confirmed by the pressure rating of the material, the resistance to slow crack growth, the resistance to rapid crack propagation and the performance of the butt fusion joints. Some practical reasons, as well as safety precautions to guarantee the long-term safe operation, led to the decision to mount sliding spiders on the PE pipe. The gaps between the PE pipe and the host pipe were sealed after pressure testing and acceptance of the installation.
