Cooldown of Large Pipes During the Commissioning Phase of Cryogenic Facilities

摘要

During day to day operations of LNG receiving terminals, process pipes are at uniform cryogenictemperatures (around ‐260°F) and experience relatively low thermal stresses. However, since suchfacilities are built at ambient conditions, fast temperature changes and high local temperaturedifferences will occur during the initial cooldown. Pipe design and its cooldown schedule therefore needparticular attention to ensure pipe integrity and to minimize leaks.During cooldown, pipes experience large tensile stresses when they first encounter LNG. As a biggerfraction of their circumference is cooled down, pipes will tend to deform and move. Pipe motion canresult in large forces that must be minimized by designing support strategies that can accommodatesuch pipe motion.This paper addresses the magnitude of the stresses that can be expected during a cooldown fordifferent pipe sizes. Cooldown strategies such as shock cooling with cryogenic liquid and precoolingwith vapor are also discussed.