05:09 Jun-19-2009 Danfer Engineering Peru, Joined Jun 2009 11
Acceptace Criteria with AUT TOFD with Code Case 2235
I not understad acceptace criteria in Code Case 2253 for plate 1in thickness, because in table 1 said for subsurface maximum lenght is 0.25 in, but in para. (4)(2) said maximum allow flaw is 4T.
Why is diferent acceptace criteria for subsurface indication.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Danfer at 05:09 Jun-19-2009 (Opening).
Dear Danfer if your plate thickness is 1 inch your acceptance criteria will be based on Table 2, Table 1 acceptance criteria is for Less the 1 Inch. if your plate thickness is 25 mm then acceptable sub surface flaw upto 100 mm with an height upto 1.7 mm is accepted, if you need further clarification u can contact me.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Abbas Bombaywala at 10:25 Jun-19-2009 .
Thank you for you faster answer.
But, I like understad the accptace criteria for plate less the 1in.
for indication subsurface. Table 1 said maximum leght is 6.4 mm, but in par.(4)(2) maximum allow is 4T.
00:46 Jun-20-2009 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1211
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Abbas Bombaywala at 21:31 Jun-19-2009 .
The issue of length in Table 1 of the CC2235-9 is an interesting topic. We have worked with Fitness-for-purpose acceptance criteria in Canada since the 1980s. The tabulated values in CC2235 have been very awkward compared to the curves we have been accustomed to for the past 20+ years. However I have managed to assemble Excel charts that allow the easier treatment of the tabulated values by converting them to the more typical curves with flaw height versus allowed length. When we use the curves it is easy to locate the flaw as either above or below the curve (see typical curve in Figure 6 in http://www.ndt.net/article/apcndt2006/papers/71.pdf). If below the curve the flaw is acceptable and if above it is rejected.
Table 1 in CC2235-9 makes it very difficult to apply the "above and below the curve" concepts; however, I think they still apply. In all FFP cases the primary dimension of concern is flaw height. Therefore for CC2235 Table 1 indicates the allowed height limit as a ratio of a/t (column 1) and if that height is exceded the allowed length is given in column 2 (6.4mm). Some people seem to think that EITHER criteria exceded constitutes an unacceptable state. But such treatment contradicts the well-established treatment given in fracture mechanics where we have been using curves. Even the API 1104 method can be seen to use the concept of the curve, but attempts to simplify the process by using 2 steps in the curve.
The clause i) (c) in 2235-9 does not state that it is restricted to just tables 2 and 3. And this fact should also add credance to the use of the "curve concepts" to Table 1. To be consistent with tables 2 and 3 in ASME CC2235 (and other codes such as BS 7910, CSA Z662 and API 1104, that use curves) I have interpreted Table 1 to mean that a flaw exceeding the allowed height is permitted a maximum length of 6.4mm. Further, any flaw exceeding the evaluation level but less than the maximum allowed height for a subsurface flaw is not to exceed 4t in length. This then makes the clause i) (c) consistent throughout the entire range addressed.
There are still shortcomings in ASME CC2235-9.
Not stated in ASME CC2235-9 is how to treat a surface flaw that is less than the allowed flaw height (regardless of which table you use). I would suspect that some maximum length would also be imposed but it is not defined in the document.
Also not indicated in the tables in CC2235 is the maximum flaw height above which no length is allowed. In the other Codes I mention above this is typically 50% wall.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Ed Ginzel at 00:46 Jun-20-2009 .
Dear Ed The clause of acceptable flaw length of 4t suggest that any indication with the length more then 4 times the thickness is rejected regardless to the values of table 1 2 & 3, So from where i think this clause is to make the rejection rate more stingent,
I had this same question in my mind before and when i asked my Level III he told me that we will first follow the values of table 1, 2 & 3 and if the values are below acceptable limit then only we will go for that caluse,
So in this case if my plate thickness is 20 mm the acceptable length of the indication is 6.4 only upto the height of 5.72 and not 80 mm if the height is below 5.72. And if my plate thickness is 50 mm the acceptable length is 200 mm upto the height of 3.40, indication with length of 201 mm is rejected regardless to its height.
This is my views
I would like to have your opinion on this.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Abbas Bombaywala at 09:51 Jun-21-2009 .
Here is a link to a program Ed and I put together to help people with this code case in flaw evaluation using these tables. AMSE really needs to re-evaluated this code and how it is written because it can be interpreted in many different ways; for example: When running the calculations for subsurface flaws, you should use the 1/2 height flaw value (a) and not the full height value (2a) which a lot of people are doing. The table asks for (a) only, so if you have a sub surface flaw of 0.100", you use the value of 0.050" for (a). This is not explained in the code and needs to be illistrated more clearly and maybe implement some examples so that people can get a better understanding of how this code works.
Here is the link:
You will need to be connected to the internet to install this program.
23:55 Jun-25-2009 Larry Mullins Consultant NxtNdT, USA, Joined Apr 2006 7
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Bill Blanshan at 15:58 Jun-25-2009 .
ASME Codes are written as minimum standard to be met for (new) construction of pressure retaining items to which they apply. Most government and insuring agencies have seen fit to adopt them into regulation or law. It is the not the authority of any group non-ASME or non-jurisdictional individual to do this. Dissenting persons need to work either with ASME or with the regulator to change the rules, and not to rewrite rules as seen fit.
Some people may not recognize that NDT Forum is a place of well-intended opinions - many very good ones, but none that will hold up in court. It may also be a grand source for spreadsheets and programs intended to aid interpretation, but the examiner and the vessel manufacturer retain responsibility.
ASME Section VIII Div 1 and the B31 documents are not sophisticated analytical engineering standards they are rules-based Codes with simple and conservative engineered minimums. They provide neat and compact rules for design, materials, fabrication, examination, test and inspection. Analysis can be used to add requirements. It cannot delete requirements. When minimums are not met the item does not meet Code and it may become a SPECIAL item, subject to alternative certification outside Code stamping.
The purchaser of an ASME stamped item has the right to assume all requirements are met. Anything less is unacceptable and violates ASME rules and possibly state, federal or provincial regulations. ASME and their adopting jurisdictions expect rules to be followed. ASME will formally interpret questionable Code areas. When there are Code questions, seek Code answers.
One further comment there are few if any mandatory in-service inspection programs for non-nuclear ASME applications. ASME, in the absence of an assured in-service program must assume the vessel will not be monitored during its lifetime. If in-service exams could be assured ASME might be able to reduce conservatism, but this is not the case. Therefore the flaw size at construction must be small enough to last the vessel lifetime.
And a further, further comment. For a standard ASME vessel the only required and assured lasting documentation it the nameplate. If the vessel is registered with the National Board there should be a Manufacturers Data Report but it is reasonable to assume that vessel pedigree will be lost except for the nameplate the point is, much if not all of the documentation for the vessel will likely be lost with time, so traceability to analysis and assumptions beyond those of the Code of record will be lost to future users nameplate integrity must be retained Code compliance must be complete.
15:26 Jun-28-2009 John O'Brien Consultant, - Chevron ETC , USA, Joined Jan 2000 278
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Larry Mullins at 23:55 Jun-25-2009 .
CC 2235-9 is a flawed document if you excuse the pun and this thread is one of only many I have seen regarding the lack of clarity on the CC and problems that arise in interpretation in use. This is actually supported by the fact that I believe ASME is now preparing a guide to interpreting the CC (why they don't just fix the CC I don't know).
It would be an ideal opportunity to supply all comments to ASME as soon a spossible so these might be addressed. I believe Michael Moles at Olympus may be heavily engaged with this work or write/email directly to ASME but don't wait or we will go more years with an inadequete interpretation around te industry.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to John O'Brien at 15:26 Jun-28-2009 .
John: You are correct as usual. ASME is writing a new "code case" for AUT, but it will be a Mandatory Appendix in Section V. One of the problems with CC 2235 - from an NDE perspective - is that the Code Case comes from ASME Sections I and VIII, not V, so Section V cannot amend it. But, as you point out, relief is at hand. ASME is working on an Interpretation Manual, and we will have Mandatory AUT Appendices soon.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Michael Moles at 16:52 Jun-28-2009 .
Mr Moles, would you be welling to put something together on this thread which can be used as an aid for everybody on the do's and dont's of this codecase? Waiting for the new code does nobody anygood at this time and it will also cost money if a purchase the latest ASME code is needed. I think it is about time a "how to manual" be plublished on this code case free to the plublic. Same request goes to Mr Ginzel if interested......Let us know. Thanks.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Bill Blanshan at 22:29 Jun-28-2009 .
Your Software is giving following error message
"Unable to Locate the label view Run-Time Engine"
"UT Weld Flaw Potter requires a version 8.5 (or compatible) labview run time -engine. Please contact the vendor of UT Weld flaw potter to correct this problem"
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Bill Blanshan at 14:31 Jun-29-2009 .
I made a slight change to the 2235 flaw calculator; the graph had default X and Y axis labeling showing "time" and "Amplitude" so I removed them so it would not be confusing (a Labview thing). Here is the updated software for download:
If anybody out the has any more suggestions or comments, please feel free to share them with me so we can make this code case much more user friendly to the technicians using it.
11:43 Jul-17-2009 gajendran NDT Inspector India, Joined Jul 2009 4
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Abbas Bombaywala at 07:17 Jun-29-2009 .
Good day to you. I am having problem to understand the acceptance criteria TOFD ASME 2235-9 table 1, 2 and 3. Its too complicated. I understood about the table calculation.
1. The acceptance criteria not straight forward. Its base on height and length of the indication. Can you please let me know how to apply these acceptance criteria?
2. TOFD indication usually we crosscheck using pulse echo. Most of the indication signal we received from TOFD scans are not defect when crosscheck with pulse echo. How to solve this problem? What we suppose to answer the client if they question us that TOFD scans got indication but not in pulse echo?
3. Can we finalize the indication without crosscheck with pulse echo? If they didnt found any indication base on TOFD scans when repair, it will be a problem for us.
4. Please refer to the attach scans. There are a lot of indication appear in the scans. How to interpret this scans base on ASME 2235-9 TABLE 2?
Please help us to understand. Your co-operation very much appreciated.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to gajendran at 11:43 Jul-17-2009 .
TOFD is an amplitude based techinque, it is the most sensitive UT Technique, The small pores also shows off with an high amplitude, The scan which u have shown seams that there is a indications near to the top surface of your scanning side if u have an access from other side u can scan it from other side and easily interpretate it.
You cant mix any other NDT Techniques for acceptance and rejection, you can always use other method for cross checking it.
In TOFD the only problem is Near Field due to Near Field the upper 6 to 7 mm of thickness is merged in the Lateral Wave. To get rid of these u can use the high frequency probe with a steeper Angle, or u can use Creep wave probes to get rid of this problem.
In your image it clearly indicates that the indications are in upper 1/3 of the weld.
14:18 Jul-17-2009 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1211
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to gajendran at 11:43 Jul-17-2009 .
As noted, Table 2 in the CC2235 is a bit complicated to use, but the software noted by Bill Blanshan can help sort out that aspect.
In your second point you state "Most of the indication signal we received from TOFD scans are not defect when crosscheck with pulse echo." The advice by Abbas is correct in that TOFD can be a VERY sensitive technique. When you "cross-check" with pulse-echo and it is based on Art. 4 pulse-echo sensitivity levels you will have an evaluation threhold. TOFD has no such threshold so you are obliged to evaluate every signal displayed. However, both TOFD and pulse-echo have the same assessment requriements in the acceptance tables; i.e. you are to determine if the critical flaw height has been exceeded. Near the test surface this will be difficult for the TOFD due to the small time-separations. Therefore pulse-echo options may be necessary. Remember, CC2235-9 also requires that you have demonstrated your technique to be capable of detecting (and sizing) flaws of the critical size on both surfaces as well as the subsurface. So in answer to your third question, yes, you can use the pulse-echo to "size" the indications detected by TOFD. If they are less than the size in the chart you can accept them.
No doubt you will have no problems sizing the 2 flaws seen on the far surface just less than half way across the scan from the left in your image. Only after they are sized can you decide if they are acceptable indications or rejectable Defects.
The CC2235 allows you to use "whatever works", but it also builds into the wording the obligation that you have demonstrated the ability to Detect critical sized flaws on both surfaces and the subsurface. It also makes provision that other "manual" sizing techniques may be used. If your technique does not accomplish the detection and sizing requirements then you may need to correct the technique.
Many users of the CC2235 are now finding that the combined TOFD and pulse-echo provides the best results. In fact, Art. 4 in ASME V "requires" that you augment TOFD with pulse-echo to address the dead-zone regions associated with TOFD. Some might then argue that there is therefore no reason to use TOFD if you still must use pulse-echo. Perhaps, but I have analysed thousands of welds with both techniques. When I have a scan that is just pulse-echo and the TOFD data is not present, I am constantly wondering if signals I am looking at originate from flaws or geometric sources. TOFD has been a great benefit to eliminate unnecessary repairs because it is generally free from the annoying signals from root and cap geometries!
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Ed Ginzel at 14:18 Jul-17-2009 .
I would like you to clear my doubt regarding using different NDT Techniques for acceptance and rejection. Once we were performing ToFD on a reactor. When we performed ToFD on the circ seam there was a lots of defects we cross checked with RT and Manual UT and those deffects were coming in acceptable range for RT and Manual UT. We told the client that we can accept this joints as per RT & Manual UT and the joints are unacceptable as per ToFD. Client told us that NDT method was decided and demonstrate before the manufacturing started for Reactor, and was approved by the End User and now we cant use other NDT Technique just because its unacceptable in the approved technique.
Because when we are performing ToFD we are repairing the repairs which really does not have much effects on the Weld strength. Most of the weld failures are in HAZ area and when we are performing repairs we are damaging the intergrity of HAZ area. So i think that any weld should be properly examined by different techniques before repairing it. Please let me know any code reference which allows us to use different NDT Techniques and size the correct deffects and then decide wether to repair it or not.
Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to Abbas Bombaywala at 12:35 Jul-17-2009 .
Abbas, I do believe you meant to say that TOFD is a NON-Amplitude based inspection technique. You are dealing with both reflected and diffracted signals so it is near impossible to do a "amplitude" based TOFD inspection where as diffracted signals are a lot weaker than reflected signals therefore you will have varying results. Furthermore, I also believe you meant to say "Near surface deadzone" rather than "near field", just so there is not confussion.
Gajendran , The problem with non-amplitude based inspections using TOFD is what do you do when you detect faint diffracted signals as seen in the image you provided (the ones located in the upper 1/3 of the weld). 99 out of 100 times, these faint flaws will not be detected with an Art. 4 weld calibrated manual pulse echo technique and if you are inspecting a weld to 2235, you cannot use other pulse echo acceptance criteria to clear the weld. So what do you do? Well, in non amplitude based inspection, you have to follow the rules and if anomalies were detected with lengths greater than the investigative lengths specified in the 2235 criteria (i)(b), you must investigate the flaws further. In this case, the term investigate only refers to characterization, location and sizing of the flaws using the same technique or other techniques such as manual UT; however this supplemental examination must be qualified during the demonstration process, but you still cannot change the acceptance criteria and you have to use the charts provided in the code. Base on the scan image, unfortunately you WILL have to size each of the upper third flaws detected by TOFD and grade them per the 2235 chart criteria even though in reality they may be very minute in comparison with manual UT criteria; this is the down side to non-amplitude based inspection techniques.
One thing I did notice in the scan image is that this weld appears to be a heavy-wall weld therefore two or more zone scans should have been performed; say one on the upper third of the weld and one focused at the lower third of the weld. The upper third scan would have depicted the flaws better and would make sizing and evaluation a lot easier. The upper 1/3 exam would require higher frequencies probes with smaller diameter crystals to provide better spatial resolution and clarity, and most likely higher refracted angles due to the size of the weld cap.
The flaw the concerns me the most is the one located at or near the I.D. If you have access to the ID surface, you will need to perform a surface examination (MT, PT, ET) to determine if it is indeed surface connected; this supplemental examination will aid in how you grade the flaw using the charts.
21:55 Aug-27-2011 massimo carminati Consultant, AUT specialist IMG Ultrasuoni Srl, Italy, Joined Apr 2007 691
Re: Re: Acceptace Criteria with AUT TOFD with Code Case 2235In Reply to gajendran at 11:43 Jul-17-2009 .
there are a lot of information missing in you image:
thickess and scan length first, angle and PCS second.
You cannot evaluate any TOFD scan without these primary information.
This makes the "relevant to non relevant discrimination" impossible and this is based on length, according to the code; length measuremet has to be demonstrated on discrete length planar defects and then applied, for every tofd pair used.
In addition, it looks that this evaluation is complicated by the quality of the scan you provided: First of all the requirement of signal duration of ASME code is not fulfilled and this makes the height discrimination based on TOF difference from tips impossible on small defects. Second, it appears to me that the surface condition is not enough smooth. If you have a good scan in terms of signal and scancondition, then you can primarily and safely exclude from computation and cross check evaluation the non relevant indication, otherwise not.
Last point, it seems to me you might have a transverse defect close to outer surface at the beginning of the scan.