Displacement of Wellhead

Hi
How should be considered the movement of wellhead in offshore project in input of Caesar II file and load cases according to below criteria?
“For pipe work connected to the wellhead, vertical movements at the Christmas tree of
+150 mm and -50 mm will be catered for. Additionally, horizontal movements of ±25
mm have been considered.”

Hi Analyzer,

Please refer Det Norske Veritas Recommended Practice, DNV-RP-D101 - Structural Analysis of Piping Systems. This may give you more information for your case. It is easy download from google search...

As "externally imposed displacements"

Define them as follows (example):

D7 (dx=25, dy=0, dz=0)
D8 (dx=0, dy=50, dz=0)
D9 (dx=0, dy=0, dz=25)

then combine the displacements as follows and add them at the end of W+T1+P1 (OPE)

D7+3D8
-D7+3D8
D9+3D8
-D9+3D8
0.707D7+0.707D9+3D8
-0.707D7+0.707D9+3D8
0.707D7-0.707D9+3D8
-0.707D7-0.707D9+3D8
D7-D8
-D7-D8
D9-D8
-D9-D8
0.707D7+0.707D9-D8
-0.707D7+0.707D9-D8
0.707D7-0.707D9-D8
-0.707D7-0.707D9-D8


After you built these additional 16 operating load cases, construct your expansion load cases. That's it.

Regards,

DNV-RP-D101 is so good that I placed on my desktop.

The pipe connecting to this wellhead has 2 design temperatures(-30&100 degrees Celsius),Do these displacements(+25,+150 & -25,-50) happen at temperatures (-30 & +100) respectively ?

I do not think so. Maybe two sets: 16 loadcases at T1 and 16 loadcases at T2 are more appropiate.
Ask process / mechanical enginner about this.

Regards,

what is the cause of these displacements of wellhead?(temperature or wave)

MoverZ can give more details:

http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=40004&page=1

Apart of this, go talk with the specialist. You belong to a team. The person that give you the information should know (I suppose ) the source of displacements.

Regards,

Thanks for your reference,
do you have any reference for allowable load of x-mass tree(wellhead)?

No, I do not have. I think API have something but I do not remember well.The best thing you can do is to contact your manufacturer and to work with him. They want to help you because they also do not want trouble.

Regards,