Farhad,

Just a slight correction.

You are entirely right for un-restrained pipeline (typically AG pipeline, or UG pipeline treated as un-restrained / FAC = 0.001 in CII). As per para. 402.5.2 "NOTE", the "thermal stress should be calculated for the range of minimum and maximum operating temperatures".

However, for fully restrained pipeline (UG pipeline), as per para. 402.5.1, thermal expansion stress should be assessed between Installation and Operating Temperatures. The designer IS NOT OBLIGED to use the Maximum Range between Minimum and Maximum Operating Temperatures.

Regards,