Tue, 05 July, 2022
The work of the Non-metallic Innovation Centre (NIC) was highlighted through two presentations at the 20th European Conference on Composite Materials (ECCM20), which took place in Lausanne, Switzerland from 26-30 June 2022.
This was the first time the event had taken place in four years, and TWI’s Chris Worrall and Maciej Gierulski of the University of Sheffield both gave presentations related to composite pipe joining.
The conference is organised by the Ecole Polytechnique Fédérale de Lausanne’s (EPFL) composite construction laboratory (CCLab) and laboratory for processing of advanced composites (LPAC), bringing together participants from academia and industry with a common interest in composite materials.
This year’s conference theme was ‘Composites meet Sustainability,’ and included a focus on sustainability factors such as bio-composites, energy efficiency in materials production, and end-of-life scenarios and recycling. This focus worked alongside the usual topics discussed at the conference through a range of plenary talks, keynote lectures, presentations and an exhibition area.
Chris Worrall’s presentation at ECCN 2022 took the subject of ‘Novel Joining Solutions for Thermoset-Thermoset Composite Pipes.’ Thousands of kilometres of reinforced thermosetting resin (RTR) pipes are installed around the globe each year for critical applications like high-pressure water injection and sour crude oil flowlines.
RTR refers to a broad family of fibre reinforced plastic pipes manufactured via a filament wounding process, where the reinforcement is generally glass fibre and the resin is a thermoset polymer, depending on the service temperature and the nature of the fluids to be transported through the pipe. These pipes are typically produced in lengths of around 10-12 metres and transported to site for assembly. The joints between these sections of pipes are often the limiting component towards a higher operating envelope, with most failures and leaks experienced by oil and gas operators being associated with joint failures.
The NIC has been working to improve RTR pipe joining techniques to eliminate failures and increase the confidence in the technology. This has involved importing modified non-metallic welding approaches used for aerospace-sector technologies to replace the current adhesive bonding solutions. This joining concept offers an approach without the need for rigorous quality control to be carried out in the field, providing an alternative solution for joining conventional RTR pipes and opening up new opportunities in future hydrogen distribution networks.
Chris’ presentation demonstrated the issues with adhesion for joining RTR pipes for oil and gas industry applications, while also demonstrating the latest work from the NIC to develop the joining process for oil and gas use and provide an insight into what is happening at the interface between the thermoset and thermoplastic.
Maciej Gierulski’s ECCN 2022 presentation took the title of ‘Electrofusion Welding of Thermoplastic Composite Pipes.’
Thermoplastic pipes are used as the main system for gas, water or sewage distribution and are often joined with electrofusion (EF) couplers. This coupling technology is mature, simple to use, cheap and reliable, with the joints being maintenance-free for up to 50 years. By contrast, the oil and gas industry has relied on the higher mechanical properties provided by steel pipes but, while they are strong and can contain high pressures, they are also prone to corrosion and difficult to install and maintain.
Recent developments in thermoplastic composite pipe (TCP) technology have shown mechanical properties as good or better than with steel pipes, providing a viable alternative for the oil and gas industry. However, as they are still being joined with steel joints, work has been underway to develop fully thermoplastic solutions using EF joints that will outperform steel couplings.
To achieve this, a standard PE EF fitting was welded with TCPs before being subjected to a whole pipe tensile test and hydrostatic pressure testing. Simultaneously, a finite element model of the joint was built and then validated using the measurements generated during these tests. The experiment sought to deliver suitable input data on the mechanical performance different layers in the TCP, which required the creation of non-standard specimen tests to account for the manner in which TCP materials are produced by tape winding.
Both of these presentations delivered insights into how the NIC is working to promote advances in non-metallic materials use, particularly for the oil and gas industry.