I´m currently working on a pipe riser for an offshore fixed platform. It is client requirement to use API RP 1111 code. (According to this code it would apply all the way up to the pig launcher/receivers)

Wall thickness for the pipe according to API RP 1111 is thinner than the minimum thickness required for B31.8 Chapter VIII? (using f1 0.5 hoop stress design factor for platform piping and risers)

Is it possible to consider 0.72 pipeline hoop stress design factor for the analysis of the riser (according to API RP 1111, "launching and receivig facilities inclusive of the associated valves for pipeline cleaning/inspection devices shall be considered part of the pipeline from a design stand point"),

Or to calculate an equivalent design factor based on the thickness obtained from API RP 1111 on the b31.8 chapter VIII equations (1) and (2)?


Or is it just not possible to evaluate API RP 1111 with CAesar II?

The following link might be helpful for you


http://asme-ipti.org/attachments/files/1288/Limit%20State%20Design%20Paper%20(IOPF2011-1003).pdf

This is the presentation you may find useful

http://asme-ipti.org/attachments/files/1286/HPHT%20Design%20Presentation%20(ASME%20IOPF2011-1003).pdf

Thank you Ibrahim.

I have seen this information. According to this document design factors for ASME codes ar based on SMYS, but for API RP 1111 is equations based on Burst Pressure (Higher than design).

For this project the software to be used is CASESAR II, so i´m trying to figure out how can i make a stress analysis using CAESAR and an equivalent design factor between API RP 1111 and B31.8 (if possible)

Would it be reasonable to proceed as follows?
- First we perform the design pressure calculation applying the hoop stress eqquation as per API RP 1111 in order to obtain the minimum wall thickness for the riser.
- Then we analyze the longitudinal and combined stress as per ASME B31.8 chapter VIII using a stress analysis software.
- In order to avoid obtaining hoop “overstress” in the stress analysis as per B31.8, i propose to apply a “equivalent design factor” for hoop stress F1, based on the wall thickness obtained from API RP 1111

I would not use the B31.8 or API RP 1111 for the design of pig lounchers/receivers. The main reason is the design of the barrel under the external loads/support loading. Local stresses are not easy to take into consideration with the pipeline codes. This is possible and a lot easier by assigning one of the pressure vessel design code for the design of barrels upto the first flange connection with piping.

I do not have API RP 1111, however I am sensing that it is not the code you need to use for the pig lounchers/receivers since it is not based on the allowable stress method. There may be a possible conversion but this is not going to satisfy anyone involved.

I suggest you discuss the issues with your client for the replacement with pressure vessel design code on barrel design only because it will be the only reliable code to use and local stress evaluation is possible.

Hope it helps.

Ibrahim Demir

Luis,

I am looking at the API RP 1111 Figure 1-Scope of API Recommended Practice 1111, it tells me that "API RP 111 applies to pipeline starting at the first incoming or last outgoing block valve on production facilities" for the Production Platform (fixed or floating).

So it is not applicable to the pig louncher/receiver in case there is a valve between pipeline and pigging barrel.

Ibrahim Demir

This is another useful paper for API RP 1111:

http://e-book.lib.sjtu.edu.cn/isope2001/pdffiles/papers/137.pdf

Ibrahim

Tahnks for the input

Accroding to the scope of work for API RP 1111 in the lastest edition (4th) if you review the definition for platform piping it states:

"Piping Restricted to a production or transportation hub platform, confined to the platform or is located between launching and receiving traps or the first boarding SDV and the last outgoing block valve if no traps are present"

According to this i have to apply API RP 1111 all the way up to the pig launcher nozzle.

From what i have seen it is not possible to use CAESAR II to evaluate according to this code.

Hi,

What I normally do is to make hand calculations following API 1111 to check for collapse when you have the piping in water and there is no internal pressure yet.
Any use the ASME B31.8 Ch. VIII for subsea operation cases.