Thermal bowing phenomenon occurs when horizontal pipe is filled partially by hot or cold fluid (LNG). Many thermal bowing occurrences cause unexpected damage to the piping or supporting structure. Since thermal bowing occurs mostly at transient conditions, such as during startup, the bowing phenomenon may go unnoticed until the damages are discovered.
It can also occur when one side of the pipe is exposed to the sun and the other side is in the shade.
This effect take place when the temperature difference between top and bottom of the pipe section is significant. It called thermal gradient. This thermal gradient causes pipe thermal strains which produce pipe curvature called thermal bowing.
- Thermal strain distribution across the pipe section is linear
- Applied only for horizontal pipes that meet “horizontal tolerance” criteria |DZ| / ( DX^2 + DY^2 + DZ^2 )^0.5 < Tolerance
- Bowing is acting only in vertical plane
Thermal gradient can be different for each pipe element. And also it can be different in each operation mode.
Thermal gradient (Ttop-Tbottom) should be specified in pipe properties.