Reinforced thermoplastic pipeline (RTP) systems for gas distribution

Presently for pressures up to about 10 bar, plastic pipeline materials (like PE ) are the preferred option. Up to now a suitable plastic pipeline system for pressures up to about 16 bar is not available. In this paper a tailor-made fibre-reinforced thermoplastic pipeline (RTP) system (pipes and joints ) is described, which is a cost-effective option for use in gas distribution systems up to about 20 bar. Development and qualification of such a system was a joint effort of various European gas companies, universities and test institutes, and a pipeline and fitting manufacturer.
To date RTP has been used primarily in oil, gas and water applications at high pressures, where the material has proven to be more cost-effective than steel. The suitability of the RTP system has been assessed by performing many mechanical and physical tests on the system components and joints. Much attention has been given to determine the long-term behaviour under internal pressure. The resistance to third party damage has also been assessed by carrying out full-scale field tests. Special attention has been given to develop a relatively simple and cheap jointing technique, based on the well-proven electrofusion jointing technique for conventional PE pipelines. In long-term tests it has been shown that the strength of these joints outperforms the strength of the pipeline materials. It is also shown that this new pipeline system fulfils the requirements of recently issued (draft) specifications for such pipeline systems for gas ( e.g. ISO and German (DVGW) specifications ). The results of the various physical and mechanical tests show that this RTP system has a performance fulfilling all the requirements of the (draft) international specifications. The long-term (50-year) strength of this system exceeds 42 bar and in all tests the joints are stronger than the pipeline material. The RTP system is also resistant to third party digging activities. The RTP system is a cost-effective option for situations where long lengths of pipes can be installed, like so-called ploughing techniques. In these situations the pipes can be installed in long lengths (200 to 300 meters ) from coils. In this case only a few joints have to be made, thereby reducing construction costs. Compared to steel systems, considerable cost reductions, in the order of 25 %, can be obtained. Presently these RTP systems are available in 4” (100 mm ) and 5” (125 mm).