For cryogenic / LNG systems, two phenomena have to be considered in expansion/contraction movement of the piping and insulation.
The first is the contraction and expansion of the materials involved due to the temperature difference between the operational inner surface and the outer surface exposed to the environment. This is considered as thermal expansion/contraction. It has three components: longitudinal, radial and circumferential.
The second phenomenon is due to the movement of the whole piping system during change of operational conditions. In particular at the bends/elbows, this can cause additional mechanical bending expansion/contraction due to the longitudinal thermal expansion.
In cryogenic / LNG services mainly austenitic stainless steel (SS) is used because of its good low temperature characteristics and stable quality. However, due to its large coefficient of linear expansion, such piping require mechanism such as be