Re-rate Questions 2

[PipingEquipment]

There seems to be a discrepancy between us and a customer. Maybe the experts on here can help out?
When evaluating a vessel for re-rate is it correct to use the code standards from when it was built, or should we be using the current standards (safety factor of 3.5 instead of 4, new material stress values vs old)?

Thank you in advance for the help.

 

[stanweld]

You can use the 3.5 to 1 saftey factor to rerate provided all NBIC and Code requirements are satisfied.

 

[jte]

... And the local Jurisdiction is ok with it. Don't bother asking to rerate to the "new allowables" in California.

jt

 

[PipingEquipment]

Ok, that's what we thought. Thanks!

 

[metengr]

This has been asked many times in the past. The original code of construction mentioned in the NBIC refers to code of construction - ASME or other, not the edition or addendum.

Second, you can use the current code of construction for a re-rate provided as mentioned above you follow 3.4.2 in Part 3 of the NBIC, the vessel is not used for lethal service and the Jurisdiction approves.

 

[brandonb73]

Ditto on what jte said. We are facing this right now in California altering a 1950 vessel. They are making us use the original 4:1 SF for design calculaitons.

 

[Christine74]

Yes, in compliance with the following minimum criteria:

a. The “R” Certificate Holder verifies (by calculations and other means)
that the re-rated item can be satisfactorily operated at the new service
conditions (e.g., stiffness, buckling, external mechanical loadings, etc.),
b. The pressure-retaining item is not used for lethal service,
c. The pressure-retaining item is not in high-cycle operation or fatigue
service (i.e., loadings other than primary membrane stress are
controlling design considerations.),
d. The pressure-retaining item was constructed to the 1968 Edition or
later edition/addenda of the original code of construction,
e. The pressure-retaining item is shown to comply with all relevant
requirements of the edition/addenda of the code of construction which
permits the higher allowable stress values (e.g., reinforcement,
toughness, examination, pressure testing, etc.),
f. The pressure-retaining item has a satisfactory operating history and
current inspection of the pressure-retaining item verifies that the item
exhibits no unrepaired damage (e.g., cracks, corrosion, erosion, etc.),
g. The re-rating is acceptable to the Inspector and, where required, the
jurisdiction,
h. All other requirements of Part RC are met, and
i. Use of this Interpretation is documented in the Remarks Section of
Form R2.

Taken from Question 4 of Interpretation 98-14(

http://www.nationalboard.org/SiteDocuments/NBIC/1998Interps.pdf)

-Christine