15:53 Mar-12-2009 Luis Ganhao Engineering, USA, Joined Sep 2008 25
Interpretatio of code case 2235
I have the following question in accordance with the code case 2235 for materials whose thickness is below 1 inch, the Table 1 from code case 2235 should be used, now if we need reject an indication that its dimensions are greater than the length (L ) and the ratio a /t recommended by the Table 1. Or is it sufficient if the L is higher, but the ratio is lower or the opposite?
18:58 Mar-14-2009 Nigel Armstrong Engineering, - Specialist services United Kingdom, Joined Oct 2000 1094
Re: Interpretatio of code case 2235In Reply to Luis Ganhao at 15:53 Mar-12-2009 (Opening).
I held off answering as I thought Ed Ginzel or Michael Moles or other notable experts on automated UT may answer. However you have got me - apologies!.
I think it is an either/or sutuation, that is if the defect exceeds either of the maximum allowable dimensions (a/t or l) then it is unacceptable. Any other interpretation of the criteria leads to the conclusion that a complete through-wall rupture of 6,3mm length is acceptable as it is less than 6.4mm This cannot be the case. Thus a defect greater than 6.4mm but meeting the remaining fraction wall thickness requirement of Table 1 is also rejectable. The Owner should be aware that using 2235 on thinner materials does not mean a relaxation of maximum allowable flaw sizes.
Interested to hear how you experience the application of 2235 acceptance criteria.
20:07 Mar-14-2009 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1210
Re: Interpretatio of code case 2235In Reply to Nigel Armstrong at 18:58 Mar-14-2009 .
Notable expert...Hmmm. Thanks Nigel.
Actually there is a clause in CC2235-9 that indictes an absolute maximum and that is the limit I have assumed is to be used regardless of flaw height. The Code Case document is divided into several "sections" with the main sections "lettered" in lower case". The one identified as (i) is Data analysis and acceptance criteria. (i)4(c) addresses subsurface flaws and states "Subsurface Flaws. Flaw length (l) shall not exceed 4t."
Therefore for amplitude-based techniques any flaw over 20% reference is investigated and if it has a legth greater than 4t would be unacceptable. As for non-amplitude-based techniques (like TOFD) the identification of ANY flaw with length greater than 4t is unacceptable. TOFD is a great technique for easy analysis but there can be a severe penalty for the wide beam it uses. Small intermittent flaws can be blended together in TOFD if the spacing is small making an intermittent flaw that could be acceptable to pulse-echo unacceptable to TOFD. e.g. small aligned pores 1mm diameter separated by 4-5mm COULD appear like a continuous indication.
Assuming Table 1 acts the same as Table 2 then the first column decides whether you apply the second column. Therefore if your a/t ratio is >0.143 then your l cannot be over 6.4 mm.
4t is an additional criteria to the tables. Therefore for an 1" length could not be 4". Since anything over an 1" on the 4t applys. Does it make practical sense to reject a 0.25" on a 1", when 4" length reject is allowable on an 1 1/8" thick material?