Key Quality Aspects for a New Metallic Composite Pipe: Corrosion Testing, Welding, Weld Inspection and Manufacturing

The composite pipe system, known as XPipe™, uses high-performance adhesives to manufacture a metallic composite pipe. Both technical development and a robust manufacturing quality system are required to ensure the safe use of such novel technology. Several aspects are discussed in this paper. Firstly, the use of ultra-high strength martensitic steels in a buried, cathodically protected environment requires an understanding of their susceptibility to hydrogen embrittlement. A series of slow strain rate and constant load tests was performed under polarised conditions to establish any reduction in ductility over samples tested in air. The results are presented and implications for their use in such a system are discussed. Secondly, although the technology to perform quality welds in thin walled austenitic materials using automated orbital techniques is well established, weld inspection by radiographic techniques is not preferred due to the continuous nature of the process and safety considerations. However, the inspection of such welds by ultrasonic techniques is challenging due to the coarse grained nature of the austenitic welds and the thinness of the liner, well below the 6mm normally considered the minimum for conventional weld inspection. Therefore, Automated Ultrasonic Testing (AUT) requires optimized ultrasonic techniques. AUT capabilities and recommendations towards an optimal inspection concept will be discussed in this paper. Thirdly, the manufacture of the liner, ultra-high strength steel strip and adhesive into the XPipe™ composite pipe requires a robust manufacturing control system, which maintains traceability of the incoming materials and controls and records all the essential parameters during pipe production. This is achieved using a sophisticated SCADA system, using feedback from a variety of sensors.