A pipe-in-pipe (PiP) technology was selected to transport hot fluids through muskeg and multiple obstacles dealt with Horizontal Directional Drillings (HDDs) in Northern Alberta. The system offers both integrity and construction advantages.
• The outer pipe provides an obvious secondary barrier to any leak. It also provides the basis for a surveillance system with a sensitivity more than 1000 times the sensitivity provided by the standard mass-balance.
• The system is pre-constrained: the inner pipe is pre-heated using electrical heat tracing at a temperature such that the system, once installed, has thermal stresses reduced by half and thus permits the installation of the high-temperature pipeline in non-competent soils with no expansion loop and no external anchor.
• The insulation system between the two pipes reduces the heat loss to only 0.3 W/(m2.K), leading to a very long cool down time.
Finally, the pipe-in-pipe can be a simple solution to high-risk and/or high scrutiny areas such as HDDs, sensitive wetlands, unstable soils, etc.
