Wall Thickness Design

[Chembloke99]

I am doing wall thickness calculation for subsea pipeline based on DNV-F-101 spreadsheet. In the spreadsheet, I am stuck as I don’t know the values that I should fill for the following parameters:

M F =Static moment due to curvature in the pipe
S F =Static effective axial force
M E =Environmental moment from vessel motions and hydro dynamic forces
S E = Environmental effective axial from vessel motions and hydro dynamic forces
?F & ?E = functional and environmental strain respectively.

I have seen a reference document for 6” and P= 861 PSI pipeline, in that spread-sheet following values have been filled:

M F =empty
S F =empty
M E =54.32 (based on experiment it is 0.85 SMYS)
S E = 170(based on experiment it is 0.10 SMYS)
?F & ?E = 0 & 0.15

Can anyone explain it to me how can I find out these values for 8” pipeline and design Pressure = 1600 PSI and temp = 77 deg C.? Any help would be greatly appreciated.
Thanks.

 

[subsealinepipe]

For wall thickness calculation as per DNV-OS-F101, the follwoings shall be checked:
1) Pressure containment (buresting)
2) Local buckling - external over pressure only (system collapse)
3) Propagation buckling

In general local buckling - combined loading criteria should be checked in other assessments (i.e. free spans, upheaval/lateral buckling, installation)

What you have pointed out are functional and environmental loads required only for local buckling-combined loading criteria, and their value shall be calculated via either a FEM or manually.

Sincerely,
Amir Naghashan

 

[DSB123]

Chembloke99,
Not trying to be negative but if you are trying to use a "spreadsheet" or any other form of calculation/software then you should have a grasp of the Codal requirements and the software/spreadsheet before tackling. Just filling in numbers is not the corrct approach. I suggest you refer to someone with more competency in the type of calculation you are attempting to undertake.

 

[Chembloke99]

Thanks Amir for your reply and for your advice. In fact, I had followed what you had suggested. I took the help of few of my colleagues and found out how the values for combined loading criteria can be estimated. Many thanks once again.