Various Concepts Of Pipe-in-Pipe Design and Fabrication

摘要

PIP systems allow a range of advanced and highly efficient insulation materials to be used in achieving overall heat transfer coefficients of less than 1 W/m2K. These systems are important components of subsea developments where untreated well fluids may have to be transported large distances and wax and hydrate problems must be managed. However, as a result of this insulation, thermal expansion challenges are increased and techniques, such as probabilistic analysis, upheaval buckling, snake lay and cooling spools are employed to mitigate high-expansion loads. There is bending of the PIP joints in the S-lay, as well J-Lay. However, both sagbend and overbend stresses can be controlled by manipulating the tension, forward pushing of the vessel and use pf stinger type/geometry. However, there is no such freedom in reel-lay to control stresses while loading the pipe on the reels. The pipe must be bent to conform to the reel radius, and stay that way for many hours or perhaps days. This is unlike S-lay and J-lay stresses (both sag-bend and overbend), which exist for a short time compared with the reel-lay.