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Up Topic Welding Industry / Inspection & Qualification / Automated UT
- - By Shane Feder (****) Date 05-29-2007 23:05
Morning Gentlemen,
We are intending to replace radiography with UT on various tanks we are currently building to API 650.
As we are required to use automated UT we will be using TOFD.
Can anybody tell me if TOFD or automated UT has a separate qualification to manual UT.?
We currently have a Level 2 UT technician on site who is qualified to Cofrend (French) but we are unsure if his qualifications will satisfy the requirements of API 650.We are working in a French territory so most of our NDT technicians have French or European qualifications.
Any help would be greatly appreciated,
Regards,
Shane
Parent - - By g32141 (**) Date 05-30-2007 00:22
AUT has its own specifications just like manual UT does. TOFD is very sensitive. Most likely they have pulse echo probes looking at different zones of the weld with the TOFD used as a confirmation.

Usually a special calibration block is made from the actual job material based on the the wall thickness and bevel prep.

Sometimes more than one cal block is required depending on the different wall thicknesses or bevel preps.

The Europeans meet or exceed ASNT as far as qualifiactions are concerned. I am sure that your UT Tech is qualified to work on your tanks.
Parent - - By Shane Feder (****) Date 05-30-2007 00:45
g32141,
Thank you for your response.
What I was trying to ascertain was if he is qualified for manual UT does that mean he is qualified for TOFD or does he have to have specific TOFD qualifications.?
Regards,
Shane
Parent - - By CWI555 (*****) Date 05-30-2007 03:05
Being qualified for manual UT does not make you qualified for AUT in and of it'self. Standard A scan manual exams are no match for A,B,C,P,S, and the other myriad of data collection screens associated with AUT. The TOFD by it'self is limited to the middle thickness, supplemental transducers in the AUT system make up for what is missed by the TOFD. Which gets to the next issue. I can't think of an AUT system that doesn't have at least 4 channels, and more common 8 and more. All of these channels have to be tuned together into a system. If not done right, you end up with destructive interference, false echos, and in general crap data. This is by comparison to the single channel typically run with standard manual UT.
TOFD is only part of the equation in short.

My two cents worth.
Regards,
Gerald
Parent - By g32141 (**) Date 05-30-2007 03:27
The AUT system I work with has usually 20 channels.

Once you get the hang of it it becomes easier.

Quite a kick in the teeth when you are first trying to get your head around it. Tandem probes can do your head in if you let them.
Parent - - By g32141 (**) Date 05-30-2007 03:06 Edited 05-30-2007 03:32
If he is qualified by his company to do TOFD then he should be OK for what you need him to do.

As far as I know TOFD is company specific. You are trained how to interpret a specific TOFD setup. Usually the guys already have a 3rd party cert before they are even hired by an AUT company wether it be PCN, ASNT, CGSB or the European equivilant. EN 173 or some such I can't remember.

Some guys actually have gone through a 3rd party TOFD course. I don't think that there is a stand alone TOFD qualification.

If you want TOFD guys should look into the nuke field because those guys are really good. AUT TOFD and hand scanned TOFD are a little different. You are probably using grey scale TOFD on a computer screen. The nuke guys map out micro intergranular cracks with an A scan. I can't even think about doing that.

If you hired this company to do TOFD and he has a UT cert. than he is qualified to do your TOFD tests. If you have something personal or you don't agree with his calls that is something different.

Regards
Parent - - By CWI555 (*****) Date 05-30-2007 04:24
EN 473 was the one you where looking for.
Nuclear is where I got the experience with AUT. IGSCC is not actually that difficult once you get used to it.
Round trip tandem, delta, there are many tandem techniques. Personal never comes into it. They either know
what they are doing, and make the right calls, or they don't. At least thats my opinion for what it's worth.

Regards,
Gerald
Parent - By g32141 (**) Date 05-31-2007 04:13
I once saw a diagram that a nuke guy mapped out with TOFD and then I saw a cross section macro of the actual weld my jaw dropped. They were almost identical.

If I had to do that it would take me a week and I would still screw it up. Hats off to those guys.
Parent - - By NDTIII (***) Date 05-30-2007 04:28 Edited 05-30-2007 12:54
API 650 Para.6.3.2.2 states if UT is performed inlieu of RT, then you must follow the requirements of Appendix U. If it is performed "NOT" in lieu of radiogrpahy, then it must meet the requirements of ASME Section V, Article 5. Either way you must follow Article 5.

Article 5 now has it's own TOFD requirements in the new Mandatory Appendix III. The only real difference between App. III and other TOFD codes from what I can see is that ASME requires supplemental Shear wave examinations to cover the dead zones at the ID and OD surfaces. I believe most European Standards do not require this, but if you are working to ASME, then you must do it. That is until ASME removes it. I  have seen the far surface resolution qualified by detecting a 1mm notch in the root are of a weld, but the near surface has a 2-3mm blind spot due to the Lateral Wave.

I don't see any special requirements for Qualification and Certification of TOFD personel, but my experience shows me that the technicians should have experience with TOFD. At least a couple of years in addition to the UT experience.

As far as your French certified techncians go, they are most likely certified in accordance with a Program that meets the requirements of EN-473. EN-473 I believe is in line with ASNT's Central Certification Program, so that shouldn't be a problem.
I personally would like to see the technicians at least company qualified for TOFD in addition to UT.

You must qualify your procedure in accordance with ASME Section V, App. III.

When using Appendix U, there is an acceptance criteria already there. However, if it is conducted as part of the contract or purchase order the acceptance criteria must be as follows:

6.3.2.5 Acceptance standards shall be agreed upon by the purchaser and the manufacturer.

This is usually in the form of an ECA based acceptance criteria.

Most of the codes are beginning to recognize TOFD as a stand alone examination technique. There are some code cases based on ASME Code Case 2235. ASME B31.3 has one as well. It's called B31 Case 181.
Parent - By Shane Feder (****) Date 05-30-2007 20:40
Thanks guys, greatly appreciated.
Regards,
Shane
Parent - - By g32141 (**) Date 05-31-2007 04:35
TOFD is too sensitive too use it alone without pulse echo backup. It picks up everything less the higher portion of the weld which can be up to 6mm of depth.
Using TOFD alone in AUT might result in uneccessary repairs. I have used cal blocks that show root defects of 1mm in height. Depending on the setup sometimes they look massive like a slag line on a radiograph when in fact they are 1 mm in height. This could cause some confusion. The "crisper" the TOFD looks the better it helps.

I just use TOFD as a backup tool for the pulse echo channels. Some guys are keen enough to know when a TOFD indication might be caused by a copper touch in an automatic weld.

If my pulse echo channels see it my TOFD should as well depending on the depth of the defect. I won't reject a weld based on TOFD only unless it is really out of the ordinary.
Parent - - By NDTIII (***) Date 05-31-2007 07:27 Edited 05-31-2007 07:32
Yes I have seen those copper inclusions. They are straight vertical lines in the TOFD image.
Which system are you working with? The Shaw System or the PipeWizard? Pipelines?

The ASME codes are beginning to recognize TOFD as a stand alone technique, but I agree. It is extremely sensitive. However, ASME requires the use of Pulse Echo for examination of the Dead Zones. You can also confirm and size your indications using Pulse Echo Planar Flaw Sizing Techniques, but you would have to qualify it.
Parent - By g32141 (**) Date 05-31-2007 23:53
I worked with the Shaw system a few years ago. Now I work for a different company. I've never worked with the Pipewizard program.
I work mainly onshore pipelines now.

I have more accuracy using the TOFD to measure the height of a defect than the pulse echo. I'll leave it at that.
Up Topic Welding Industry / Inspection & Qualification / Automated UT

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