Dear all,

The system is LNG transfer line from Jetty to Storage Tank (20inches, A358 304 CL1, Design is -180c,)
Process recommended Bowing Temperature is 50c
Already finish static analysis for all the Sustain, Design and Operating conditions with safe loads on all supports.
Now start to analyse the bowing effect for the LNG system.

The query is
1. What is the temperature need to consider for analysis, whether design -180c or operating temperautre -170c or the cooling medium Nitrogen temperature to attain -120c

2. when i consider bowing 50c with operating temp -180c, i find failing occurs on the tapping location to storage tanks..

3. But the basic prinicple is in vertical lines bowing will not occur.
so, how to solve this issue... Any recomendations pls.

The process details is

For uniform cooling of equipment and piping, cold gaseous nitrogen shall be used. It is important to understand that in using LNG or liquid nitrogen for cool down, there can be a differential temperature between the top and bottom of pipe for horizontal pipes lines. If this temperature difference is too high, it can result in bending of pipes. To prevent this, a careful check shall be done for the differential temperature from top to bottom of pipes. A maximum temperature difference of 50 °C is to be maintained from top to bottom of pipes.
The system needs to be ideally cooled to -162 °C which is difficult to attain throughout the terminal due to normal heat leak. The temperature at the source of the cold gaseous nitrogen supply will be approximately -170 °C. Thus, the criteria are to cool down designated lines to approximately -120°C and not higher, prior to introducing LNG from the LNGC.

Hi,

According to the me, thermal bowing will only occur when the top of pipe and bottom of pipe will have a different temp. So if you are using operating temp as -180 deg C with thermal bowing temp as 50 deg C, Then it is correct (according to me). kindly make sure you are using the hold down guides at regular interval (not the conventional guides support).

We also had faced lots of issues because of this, it will be better if you can share the pic where it is failed, so it gets more clear.

One more thing, if the bowing is casued by end reactions on the piping system, then increased flexibility plus spring loaded support can solve your problem. Hope this helps.

Regards,
R.K.