Cryogenic expansion joint for LNG service

Abstract

Pipelines transporting cryogenic liquids, such as liquefied natural gas (LNG), are typically constructed with metal components with a relatively high thermal expansion coefficient. Pipelines contract in length due to the large temperature differential that occurs. To accommodate this thermal contraction, LNG plants, offloading jetties, and other facilities typically utilise expansion loops and/or conventional in-line expansion joints (e.g. bellows). However, expansion loops require a large amount of space and support platforms, which can be costly and/or disruptive to an LNG facility construction. Additionally, conventional bellows-type expansion joints offer very little torsional strength, which may lead to catastrophic failure in the joint. Engineers at Clough Limited have patented two unique embodiments of a cryogenic expansion joint:

• a sliding concentric pipe-in-pipe cryogenic expansion joint; and

• a torsional cryogenic expansion joint.

Both designs utilise inherent material properties to seal sequential pipeline segments together at cryogenic conditions. The pipe-in-pipe expansion joint provides large axial and unlimited torsional movement. The torsional expansion joint provides unlimited radial and some axial movement. These embodiments eliminate the large conventional expansion loops and reduce project capital expenditure.