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Re-rate Jobs: What does it mean by original code of construction
2

Re-rate Jobs: What does it mean by original code of construction

Re-rate Jobs: What does it mean by original code of construction

(OP)
Folks,

For all re-rate jobs, we usually specify that re-rate must be done as per original code of construction. In an attempt to get further information on this important point, I went through couple of old threads on this forum and found that there is a difference of opinion on this issue. Some seniors think "original code of construction" means only B & P vessel code (i-e., ASME Section VIII) and some think, "Original" means that we have to use the same edition and addendum of ASME Section VIII used in original fabrication. Please disregard, if I am interpreting explanation given in threads incorrectly.
However, one thing is common in both approaches that we have to use the old allowable design stress.

 
If I follow first approach and use wall thickness formula given in Para. 1-1 (Mandatory Appendix 1 – Section VIII Div. 1) for re-rate, which has a design factor of 3.5, in comparison with a design factor of 4.0 used in pre 1999 addenda. This will give me a reduction of approximately 12.5% in the pressure vessel minimum required wall thickness. At the same time, if I use old allowable design stress in the same formula, this will increase pressure vessel minimum required wall thickness. Overall, I will get some figure in-between 0% & 12.5% for minimum required wall thickness.


On the other hand If I use second approach and use formula from original code edition and addendum, which will use a design factor of 4.0 with old allowable design stress, I will get bigger number in comparison to above for pressure vessel minimum required wall thickness.  This seems to be a more conservative approach.

Would highly appreciate your feedback with respect to above. It will certainly help me in having a clear understanding of this topic.

Best Regards,

Meck91
 

RE: Re-rate Jobs: What does it mean by original code of construction

You can use the current edition/addenda of the original Code of construction.

RE: Re-rate Jobs: What does it mean by original code of construction

First off, for re-rates you should be using the either the National Board Inspection Code (NB-23) or API 510 to determine if the re-rate is an alteration in lieu of repair. Either of these in-service codes for re-rating provide rules for what is required if the re-rate is an alteration.

Regarding code of construction, the NBIC provides flexibility in this manner with allowing current edition/addendum of the code of construction. However, keep in mind that using the current edition/addendum of the code of construction could force a re-rate into an alteration where otherwise, could be a repair. One must be aware of all issues when it comes to re-rating and most important get your local Jurisdiction involved on the front end not the back end of a project.

RE: Re-rate Jobs: What does it mean by original code of construction

2
With regard to the NBIC, there is a site with posted interpretations which may assist you in providing information for part of your debate with your seniors.

http://www.nationalboard.org/index.aspx?pageID=14&ID=22

An interpretation from 1995 (Interpretation 95-19) has a question posed just like yours.  

RE: Re-rate Jobs: What does it mean by original code of construction

The limitations on repairs is set by Jurisdictions,
Original Code Of Constr. include ASME B&PV Code and other than ASME Codes.
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