New Technologies # 2004 Milan
Plastic pips have entered many applications and have outperformed traditional materials in many respects. Until recently, the use of thermoplastic pipe has been limited to rather low pressures, up to about 10 or 16 Bars. Since the introduction of Reinforced Thermoplastic Pipe (RTP) this situation has drastically changed. While retaining the advantages of plastic pipe, like its inherent corrosion resistance, its ease of installation (flexibility, reelability, ease of welding), and low cost of maintenance, fibre reinforcements opens the opportunity to much higher pressure and temperature rating, up to about 100 or 150 Bars at 650 C, until recently only achievable by metal pipes. RTP basically consists of 3 layers : 1. A thermoplastic (usually HDPE) liner pipe, its main function being to act as a containment of the fluid in the pipe. The liner has only limited function with regard to pressure resistance. 2. A high strength synthetic fibre reinforcement, to provide the pipe's hydraulic strength. The reinforcement usually consists of an even number of counter helically wrapped layers of textile fibre cords. The cords may be applied as flat thermoplastic ribbons, with axial cord-reinforcement. 3. A thermoplastic cover (also usually HDPE), to protect the fibres from external damage, like abrasion and UV light, and to provide a layer for electrofusion welding. Although from a mechanical point of view not absolutely required, RTP installed today is almost solely of the "bonded" structure type, where the three constituent layers are welded together to a monolithic pipe construction. A bonded pipe can be electrofusion welded, thus avoiding the use of metallic clamp type coupling systems, and avoiding the related corrosion issues. A bonded structure is usually required for gas transportation pipelines. RTP has been successfully introduced in the oil and gas industry for gathering and injection pipelines in oil and gas fields, and high pressure gas transport pipelines. This break-through has been accomplished by the introduction of appropriate standards for this new pipeline materials by the manufacturing industry and the end-users. RTP which has been qualified according to these (draft-)standards is now commercially available and has been installed in considerable quantities at major oil and gas companies.