We have one LNG line which we are analysing at -196 Deg design/ -158 Deg Operating and +38 Deg cases. We have applied bowing of 50 Deg . The queries are as under-
1. Whether CAESARII will apply bowing to all three cases ? i.e. the stresses due to bowing will be calculated for all 3 temperatures ?
2. What we find that in EXP case for 38 Deg C the stresses are more than those in -195 Deg temp case . Is this due to bowing ? Even if it is due to bowing , logically , we feel that the stresses in -195 Deg C case should be more than stresses in 38 Deg C case.
3. How bowing stresses are handled ? - Whether CAESARII calculates stresses due to "E*co-eff of thermal expansion*bow temperature" and adds it to stresses due to piping ? Any effect of ratio of liquid level and dia of pipe is taken ? When in a big bore line where piping stresses are already high , even if we model a "TEE sif" without modeling connected piping we find that the line gets overstressed since the stresses are already very high.
Regards,
Godbole

During periods when horizontal pipelines are partially filled with LNG during filling or draining operations,
temperature differentials between top and bottom of the pipe up to 60°C may occur. This will then lead to “Cryogenic bending” with consequently extra stresses, support loads and angular deflections and rotations,particularly at the elbows of the pipeline.

Stresses due to this cryogenic bending or bowing are to be classified as displacement stresses. In the calculation, the temperature differential will be assumed to be linearly distributed from top to bottom.

Temperature differentials for the various parts of the system shall be considered.

However, the design shall allow for a temperature differential of 60°C.

Weight has a hold down effect on the cryogenic bending. In evaluating the cryogenic bending, the line shall be considered to be filled only half full with LNG.

Supports uplift during cryogenic bending shall be limited to 50mmn and will be controlled with 100mm high guide thrusts

B31.3 CRYOGENIC BENDING LOAD CASES (LNG LINES)
EXECUTION CONTROL PARAMETERS (CAESAR II File)
Rigid/ExpJt Print Flag ..... 1.000
Bourdon Option ............. 1.000 (Translation only)
Loop Closure Flag .......... 1.000
Thermal Bowing Delta Temp +60.000 C
Liberal Allowable Flag ..... 1.000 (yes, if needed)
Uniform Load Option ........ 1.000 (g)
Ambient Temperature ........ 25.000 C