An Ambient Pressure Insulated LNG Pipeline for Subsea Environments

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSubsea cryogenic pipelines are emergenging technologies that are essential for the new generation of offshore LNG loading and receiving terminals. Current LNG product transfer systems use short runs of rigid or flexible pipe. As terminals move further offshore, there is a need to develop longer runs of insulated rigid pipeline LNG transfer systems.A major issue for these systems is the pipe contraction due to the low temperature of the LNG. At present, there are mainly two methods to accommodate this contraction: -Use of INVAR TM or other alloy with ultra-low thermal expansion coefficient, or -Use of bellows, one in each segment (about 50 ft long) of the pipeline, which is a self-contained pipe-in-pipe segment with vacuum insulation. While technically feasible, both methods suffer major disadvantages in cost, reliability, durability, or maintenance requirement.A new pipeline configuration has been developed to address these disadvantages. This configuration uses a highly efficient thermal nano-porous insulation in the annular space between the inner and outer pipes. This material is kept in an ambient pressure environment, which is produced through sealing by metal or non-metal bulkheads. The bulkheads transfer the contraction induced axial compression load on the inner cryogenic carrier pipe(s) to the external jacket pipe. The resulting pipeline bundle is a structural element, which addresses the thermal contraction & expansion loads without resorting to expansion bellows or ultra-low thermal contraction alloys.As an example, a LNG carrier pipe that would be rated for cryogenic service and be configured to transfer thermal loads imparted through the bulkheads would be a 9% Nickel steel, while the jacket pipe is carbon steel. The thermal insulation used in the configuration is a high performance nano-porous aerogel product, approximately 2" thick, in blanket form installed within the annular space without vacuum and under ambient pressure. This paper will discuss the techical details of the configuration, and the Phase I test performed in April 2004 using a cryogenic pipe specimen under flowing LNG conditions.

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.…”

New Flow Assurance System With High Speed Subsea Fiber Optic Monitoring of Pressure and Temperature

“…Since the initial deployment, other deployments have monitored steel catenary risers, drilling risers, tension leg platforms (TLPs), umbilical installations, touchdown zones, slugging mitigation, and subsea tiebacks ( [2][3][4][5][6][7][8]). Originally implemented in high temperature rocket motor applications, recent studies also extend this sensing technology to distributed monitoring of cryogenic liquified natural gas transfer pipelines [9].…”

Advanced Deepwater Monitoring System

“…In addition to pressure, the temperature and strain were monitored in real time. Since then other deployments utilizing fiber optic sensors were deployed on deepwater drilling risers and later on deepwater steel cantenary risers [1][2][3][4][5]. An important aspect is that the sensors do not require penetrations into the flow stream, pressure vessel, or pipe wall.…”