Managing Contraction and Stress in an Ambient Pressure Insulated 9%Ni Subsea Cryogenic Pipeline

Abstract

The interest and rapid development in the transportation of LNG world-wide has prompted a fresh-look at how LNG is transferred to/from an LNG carrier that may be moored offshore in various locations. LNG subsea pipelines are emerging technologies that are critical to a new generation of offshore LNG loading and unloading terminals. This paper addresses a cost-effective pipe-in-pipe design configuration which uses ambient pressure, high efficiency aerogel insulation and high strength 9% Nickel alloys to manage the contraction forces and stresses in an end restrained cryogenic pipeline system. The paper discusses the derivation of stresses in the pipeline and how they compare to common industry codes and recommended practices. The paper also discusses the welding development and qualifications of welding a 9% Nickel alloy steel pipe to achieve the industry's first use of matched strength welds to the parent material, a significant technology breakthrough, with suitable welding consumables and techniques successfully applied in other pipeline projects.The design discussed is based on proven industry materials and components, which have been combined together to form a new cost effective subsea LNG pipe-in-pipe configuration. The presentation discusses the review programs employed by ABS and DNV to certify the technology for project applications, which led to the award of "Fit for Service" certifications.

Embedment depth and uplift capacity of a cryogenic pipeline dynamically laid in a trench

“…Information in regards to the geometric and structural properties of proposed cryogenic pipelines were collected through a literature review (Prescott et al, 2005;Beike et al, 2009;Ballesio et al, 2009;Brown et al, 2009;Prescott & Zhang, 2009;Spitzenberger, 2009) and discussions with relevant industries. Typical diameter, bending stiffness and weight are listed in Table 1.…”