Abstract
Flexible pipe is a cost-effective and tailor made pipeline solution. Nevertheless, today's demanding market conditions call for new solutions with further increased cost effectiveness to satisfy demand for a reliable and very economical solution.
The paper will focus on a new qualified solution whereby the interlocked pressure shaped armour wire is replaced by single strip made of carbon steel wound on the pipe with 50% overlapping. A large percentage of the market is dominated by smaller diameter (<12″) pipe for low pressure, static flowline/jumper applications in shallow water, such solution will typically cover such domain range. In this paper will be covered the profile description and associated qualification tests, as well as the cost effectiveness and economic viability.
Currently, flexible pipes are suitable for a wide range of technical specifications, including inner diameters (ID) from 2″ up to 21″ ID, design pressure up 20,000psi, temperature up to 150°C and water depths to 3,000m. Such pipes are made of an interlocked pressure armour wire (shaped wires), resulting in relatively high inertia pipe, with added weight leading to manufacturing challenges and associated cost.
This new pressure armour strip profile was developed and qualified with the following outcomes:
Reliable qualification of a technology from 4″ to 12″ ID following API RP 17B process.
Significant cost reduction compared to current design in similar cases when this new technology is applied.
Simple and cost effective installation feasibility facilitated by weight optimisation and associated top tension reduction (horizontal over boarding of the flexible pipe over a gutter using a tensioner or use of low tension vertical pipelay systems).
The new pressure armour strip profile (profiling of the strip) was engineering detailed, a reliable qualification program was conducted on 6″ flexible pipe following API RP 17B process. Such qualification program implies pipe characterization against: crushing, bending, internal pressure, burst limit, and deviated tension. Finally, cost impact assessment was conducted.
Some additional benefits associated with this innovative design include the elimination of pressure armour unlocking phenomenon during service or installation and reduced gas diffusion into the annulus.