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Up Topic Welding Industry / Inspection & Qualification / peaking value
- - By krautkrammer (*) Date 07-22-2009 15:05
Hey Guys,

I am doing a spherical tank project right now and actually, we are on the completion stage.  I would like to ask if someone here knew what the allowable value for peaking of welds is. I refer on ASME VIII Div.2 (2008a) Part 6 paragraph 6.16.3 C, peaking value shall be determined using paragraph 4.14 but when you go through 4.14 it only details the evaluation of vessels outside of tolerance (i.e. shell tolerances, local thin areas).



Hope you can help me out.



Thank you



Parent - By bert lee (**) Date 07-25-2009 07:32
would you like to seek opinion from API 510 or 653 inspector? do you have in your place and know someone?
Parent - - By bert lee (**) Date 07-25-2009 07:41
"Hope you can help me out" ---- you mean boss can't help u! ):
Parent - - By 803056 (*****) Date 07-25-2009 16:32 Edited 07-25-2009 16:52
I don't have a copy of Section VIII, Division 2, but if I was forced to guess I would say "peaking" is the distortion introduced by residual stresses (from welding) that cause the plates to buckle outward. The end result is the vessel is no longer round or it doesn't have a smooth curvature in the area of the weld. You could possibly have the same result if the edges of the plates are still flat after rolling (forming) to shape.

I don't believe they are referring to the height of the face reinforcement.

Is there a glossary included with Division 2? If there is, it may define "peaking".

Best regards - Al 
Parent - By krautkrammer (*) Date 08-05-2009 10:32
Yes,you are right Al regarding the peaking, but the problem is Section VIII, Division 2 does not specified peaking tolerance as I mentioned above, not like API 650 the tolerance for peaking & banding were specified accordingly.
Parent - - By CWI555 (*****) Date 08-05-2009 11:37
I am assuming by your request, that this item is addressed as requiring a fatigue analysis.

"6.1.6.3 Peaking Of Welds in Shells and Heads For Internal Pressure
a) If a fatigue analysis is required, see paragraph 4.1.1.4 then the peaking height, p d , at Category A weld
joints shall be measured by either an inside or outside template, as appropriate (see Figure 6.1). As an
alternative, the peaking angle may be determined using the procedure described in Part 8 of API
579-1/ASME FFS-1 for materials operating outside the creep regime, or Part 10 of API 579-1/ASME
FFS-1 for materials operating within the creep regime."

If I were you, I'd be taking the allowed alternative mentioned in bold.

Regards,
Gerald
Parent - By krautkrammer (*) Date 08-06-2009 15:01
Thanks Gerald, but the paragraphs on bold font are alternative procedure for determining peaking angle not the allowable value/tolerance for peaking.

As mentioned on 6.1.6.3 c) If a fatigue analysis is required, the allowable value of dp (peaking height) shall be determined using paragraph 4.14 and shall be shown in the Manufacturer’s Design Report.

Paragraph 4.14 is an Evaluation of Vessels Outside of Tolerance
4.14.1 Shell Tolerances
If agreed to by the user, the assessment procedures in Part 5 or in API 579-1/ASME FFS-1 may be used to qualify the design of components that have shell tolerances that do not satisfy the fabrication tolerances in paragraph 4.3.2 and 4.4.4.

Anyway I gone through all the reference paragraph and found out the tolerance under 4.4.4.4,.

4.4.4.4 Spherical Shells and Formed Heads - the tolerance requirements in paragraph 4.3.2.2 shall be satisfied. In addition, the "MAXIMUM LOCAL DEVIATION" from the true circular form, e , for SPHERICAL SHELLS and ANY SPHERICAL PORTIONS of a formed head SHALL NOT EXCEED THE SHELL THICKNESS.

Finally our peaking inspections reports were accepted by owner.  :-D

Regards,

Raymund
Up Topic Welding Industry / Inspection & Qualification / peaking value

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