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08:09 Jun-03-2009
Jega
TOFD In lieu of RT as per ASME B 31.3

Gentlemen,

I was asked to carry out TOFD on piping in lieu of RT. The applicable code is ASME B 31.3

My first question is whether ASME B 31.3 allows the usage of TOFD in lieu of RT?

When checked ASME B 31.3 para 344.6.1 (Method of ultrasonic examination), it says UT shall be as per ASME SEction V Article IV. Now I can see Mandatory Appendix III describes TOFD weld examination requirements. Can I tell the client that we can use TOFD based on this mandatory appendix and prepare cal block as per Fig III-434.2.1(a) & (b)?

I understand that 344.6.2 refers to case 181 for alternative UT acceptance criteria which inturn allows the usage of TOFD. Now should I proceed with Case 181 and make cal blocks or follow mandatory appendix of Section V for TOFD isnpection?

Do I need to make cal blocks for diff dia and thickness range of piping?

Your help is much apprecaited

Jega

 
13:22 Jun-03-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1196
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Jega at 08:09 Jun-03-2009 (Opening).

Jega, B31.3 has always permitted either UT or RT as the method for volumetric assessment of pipe welds. Therefore, you are not actually doing UT in lieu of RT. The reference that B31.3 makes to ASME Section V therefore allows you to use whatever UT technique is appropriate. If you agree to use TOFD there are guidelines in Article 4. There you will see that calibration of TOFD may be done on the material being inspected (see III-463.1) and obtain a grain grass level of about 10%. But also note III-471.9, which basicaly makes TOFD auxilliary to a pulse-echo examination (required) for near surface and far surface coverage to overcome the deadzones.
TOFD is an excellent detection and sizing tool! However, with thin wall piping you may find its application with the pseudo-fracture mechanic's based acceptance criteria in CC181 much more conservative than the workmanship option in 344.6.2 of B31.3.

 
16:24 Jun-03-2009

Luis Ganhao

Engineering,
USA,
Joined Sep 2008
25
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Jega at 08:09 Jun-03-2009 (Opening).

Jega, the code case 181 permit the use of AUT (TOFD & PA) in lieu of RT, but you have to select the most appropriated setting for the examination, I mean you need to check the thickness and after that select de frequency, probe sizes and angles. Regards to the calibration block ASME Sec V and BSI-7706 or ENV-583-6 given to you the chance to perform the calibration for TOFD on the pipe material to be inspected in such sense you do not need a calibration block but for shear wave yes (this technique is necessary to check the dead zones of TOFD). I have carried out many inspections on pipelines with TOFD in lieu of RT, whose thicknesses were in the order of 9-11 mm, inclusive I could detect cracks generated by service (gas). I will send to you an image where you can observe the quality of the image and the crack detected.

 
20:05 Jun-03-2009
Jega
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Luis Ganhao at 16:24 Jun-03-2009 .

Dear Ed, Dear Luis,

Thank you so much.

Please correct me if I am wrong with following statements.

1) If I use mandatory Appendix III of ASMe B 31.3, I should make cal blocks (on plates)
based on the thickness ranges given in the appendix.

2) If I follow ASME Sec V and BSI-7706 or ENV-583-6 I can perform the calibration for TOFD
on the pipe material to be inspected in such sense I do not need a calibration block

(Of course both the above methods will be supported by Pulse Echo to get maximum
coverage)

3) The acceptance criteria of non-primary defects ( crack, LF & LP/IP) will be based on the
ASME B31.3 UT acceptance criteria

Thanks,

 
21:06 Jun-03-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1196
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Jega at 20:05 Jun-03-2009 .

Jega:
You seem to be mixing codes and requriements here.
1. Mandatory Appendix III is from Section V Art. 4 (not B31.3) and calibration blocks would be made using pipe (not plate). Appendix III permits the use of targets or grass level.
2. If you are working to ASME B31.3 there is no reference to EN583-6 or BS 7706. And since you are required to use pulse-echo in addition to TOFD to comply with ASME V Art. 4 Appen III you will still need a complete set of pipe (one for each diameter and thickness tested) to calibrate the pulse-echo setups.
3. The acceptance criteria are based on your contract speification. The criteria MAY be the workmanship you quoted or it MAY be the pseudo-fracture mechanics criteria issued in Code Case 181. Check your contract details for this. As the service provider YOU do not generally get to decide.

 
00:32 Jun-04-2009
Jega
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Ed Ginzel at 21:06 Jun-03-2009 .

Dear Ed,

Many thanks again, but mandatory appendix states piping cal blocks are not applicable!

I am confused as I cant find anything on the mandatory appendix states that we have to make TOFD blocks based on diameter where as thickness requirements are clearly stated

 
08:05 Jun-28-2009

sampeebles

Consultant,
BINDT,
United Kingdom,
Joined Jun 2009
8
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Jega at 00:32 Jun-04-2009 .

Gents,
We are currently using TOFD on carbon steel pipework to B31.3 along with conventional pulse echo to comply with ASME V app III, I as the client have understood the requirements to state we should have a complete set of blocks in same material as our pipe for each diameter but have a NDT contractor arguing that these blocks are only for when testing long seams and not when scanning parallel to the weld axis, sure I am right but would like some back-up if anybody has time.

Sam Peebles.

 
23:07 Jun-28-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1196
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to sampeebles at 08:05 Jun-28-2009 .

Sam, you are correct, but I thought I had answered this in my previous reply (point 2). Yes, ASME V, Art. 4 Appen III does allow TOFD to be calibrated on the test piece. However, since you are also required to use pulse-echo for the near and far surfaces this will require the standard notched calibration pieces for the pulse-echo setups. Since these are pipe welds the same Article requires calibration pieces be made of the same diameter and schedule as being tested.

 
23:33 Aug-17-2009

Bill Chestnut

NDT Inspector,
Self Employed,
United Kingdom,
Joined Mar 2006
3
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Ed Ginzel at 13:22 Jun-03-2009 .

Ed, thanks for your well informed responses on this topic, please forgive me if I have missed the point but does not III-463.2 refer to the method for setting gain using the lateral wave (40-90%) or when not suitable grass at 5-10%, is this not specific for non-piping only as III-464 (for piping)states that the requirements of III-464 are not applicable to the tofd technique.

As I see it sensitivity must be proved for piping on the SDH's or the notches (fig L432 non mandatory appendix)

please pardon me if I have mis-interpreted the standard but I think this was the issue that was confusing some of the guys,

 
17:14 Aug-18-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1196
Re: TOFD In lieu of RT as per ASME B 31.3 In Reply to Bill Chestnut at 23:33 Aug-17-2009 .

Bill:
I think you have made a good observation. Prior to the addition of Appendix III in Art. 4 the provision for non-distance amplitude methods (TOFD) were described for piping too! T-464.2 gave the same sort of options for either calibration blocks or material (grass) for piping. This paragraph should PROBABLY have been deleted when Appen III was added (a formal querry to ASME could resolve this...anyone interested in sending it in?). Then the same sort of description SHOULD have been made for lateral wave and grass level as options for Piping as well as non-piping.
I believe it was the intent of the Appendix to allow TOFD on piping welds in the same way as it is used on non-piping welds.
But if T-434.3 does not apply (as per III-434.3) there is no calibration block for TOFD.
And if T-464 does not apply (as per III-464) there is no TOFD calibration option for piping!

It was my initial understanding that the ASME requirements for the non-piping welds were to apply to piping welds. I do not think that, effectively, prohibiting TOFD on pipe welds was the intent of ASME in this case. However, that is not how the links read as you have appropriately pointed out!
TOFD is as effective on a pipe butt weld as it is on a non-piping butt weld! But that is my opinion after using it very successfully on piping for nearly 20 years. However, the ASME TOFD committee members may have a different idea.

But in all cases, the concern for the putative dead zones promted the extra requirement in III-471.9 for pulse-echo coverage of the root and cap areas.

Again, good observation Bill!!

 


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