Cryogenic Structural Performance of Corrugated Pipe

Abstract

One alternative to developing offshore gas reserves is to use a floating LNG plant (FLNG) on site and export the LNG using tankers. This alternative requires the use of a reliable LNG transfer system between the FLNG and the tanker under offshore conditions. One such system involves a cryogenic hose, whose main body is a vacuum insulated, pipe-in-pipe hose made of corrugated stainless steel pipe (c-pipe) and flanged terminations. Given the novelty of the transfer system, ExxonMobil conducted an experimental program to understand the structural performance of the basic c-pipe under static and cyclic loading at room and cryogenic temperatures. This paper discusses overall qualification issues and presents the experimental methodology and results of structural performance tests of the full-scale c-pipe at both ambient and cryogenic temperatures. Fourteen full-scale, c-pipe static tests are reported, including tension, compression, bending, torsion, and internal pressure. In addition, 11 axial and three pressure fatigue tests are presented. One key result is that, overall, cryogenic temperature improves structural performance for the limit states tested, indicating that future qualification at room temperature would be sufficient. Moreover, the fatigue performance at both ambient and cryogenic temperatures surpassed the design curve reported in the literature for c-pipe.