where expertise comes together - since 1996

Web's Largest Portal of Nondestructive Testing (NDT)
Open Access Database (Conference Proceedings, Articles, News), Exhibition, Forum, Network

All Forum Boards
Technical Discussions >
TOFD
Career Discussions
Job Offers
Job Seeks
Classified Ads
About NDT.net
Articles & News

4095 views
05:44 Mar-03-2005

Ananthan

Consultant,
RAA Tech Solutions,
India,
Joined Jun 2000
36
TOFD

Dear Friends,

I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?

Thanks

S S Ananthan


 
00:54 Mar-03-2005

Ton Kooren

NDT Inspector, -
NRG Nuclear Research and consultancy Group,
Netherlands,
Joined Mar 2002
3
Re: TOFD Dear Mr. Ananthan,

ToFD is an accepted NDT-technique for the inspection of butt welds in low-alloyed carbon steel in lieu of radiography having wall thicknesses between 12.7 mm (½”) and 304.8 mm (12”) and even larger, according the ASME Code Case 2235-6.

Best regards,

RTD Quality Services
Ton Kooren

----------- Start Original Message -----------
: Dear Friends,
: I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: Thanks
: S S Ananthan
------------ End Original Message ------------




 
09:12 Mar-03-2005

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
246
Re: TOFD ----------- Start Original Message -----------
: Dear Friends,
: I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: Thanks
: S S Ananthan
------------ End Original Message ------------

Is your requirement coming from a need to use Co 60 on this thickness?
If so have you considered using Computed RT using Iridium? Now accepted by ASME Code Case.



 
05:18 Mar-04-2005
Ed T.
Re: TOFD ----------- Start Original Message -----------
: : Dear Friends,
: : I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: : Thanks
: : S S Ananthan
: Is your requirement coming from a need to use Co 60 on this thickness?
: If so have you considered using Computed RT using Iridium? Now accepted by ASME Code Case.
------------ End Original Message ------------

I don't think TOFD is reliable enough to be used as a stand alone examination. You compromise your near surface resolution for one thing.
You could use Automated UT (AUT) with TOFD capabilities. There are many companies that provide this service.



 
03:11 Mar-04-2005
Simon Amallraja
Re: TOFD ----------- Start Original Message -----------
: : : Dear Friends,
: : : I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: : : Thanks
: : : S S Ananthan
: : Is your requirement coming from a need to use Co 60 on this thickness?
: : If so have you considered using Computed RT using Iridium? Now accepted by ASME Code Case.
: I don't think TOFD is reliable enough to be used as a stand alone examination. You compromise your near surface resolution for one thing.
: You could use Automated UT (AUT) with TOFD capabilities. There are many companies that provide this service.
------------ End Original Message ------------

You can discuss with Force Technology, Denmark for Automated UT with TOFD facilities. If the reqt is in India we are the Technical Co Ordinators for Force.
You can contact me: Mobile: 09866343309 / 04027818928
Mahindra Intertrade Ltd.


 
00:08 Mar-05-2005

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
Re: TOFD The first two questions you need answered are

a) Does the code of construction permit such substitution
b) Does the end user approve of such substitution.

If the answer to both is Yes then you can consider the merits and limitations of TOFD. As other answers have indicated ASME have applied acode case on this issue for pressure vessels and piping and there is a similar substitution in API 650 for storage tanks. In all cases the substitution is for computer based UT examination and TOFD happens to fill those parameters.

Many people find TOFD acceptable as a screening tool understanding the limitations at the surface. However it does have limitations on sizing and may need to be employed in use with Pulse Echo sizing techniques. You may also need to perform a surface/near surface NDE technique to ensure all possible flaws have been covered.

The subject is extensively used and discussed over the Internet but be aware interpretation of TOFD images requires training and experience and that is often the biggest limiting fcator.




 
02:10 Mar-07-2005

Michael Moles †2014 *1948

,
Joined

Re: TOFD ----------- Start Original Message -----------
: Dear Friends,
: I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: Thanks
: S S Ananthan
------------ End Original Message ------------

Anantha:

Technically you can replace RT with UT on 120 mm wall specimens, and this has been done through ASME Code Case 2235. With this code case, you will need to show that your procedure works using a Performance Demonstration. Of course, you will also need your client's approval. Both TOFD-based systems and pulse-echo type can be compatible with ASME CC 2235. We do not recommend using TOFD alone, as this will leave you with dead zones at the OD and ID; these zones can be covered off with pulse-echo probes as well. With ASME CC 2235, you will need an encoded scan and full data storage.

If you are interested, R/D Tech makes a variety of equipment for weld inspections, including phased arrays and conventional TOFD-based systems. Either contact me, or our agents in India - Blue Star Industries.

Michael Moles



 
05:36 Mar-11-2005

James Gauthier

NDT Inspector, Operations Manager
GE Inspection Services,
USA,
Joined Nov 2007
25
Re: TOFD TOFD is a great tool for weld inspection. I agree with the comment that TOFD requires experience and training with regards to analysis, however I don't think I have ever discussed sizing limitations with anyone. One of the advantages is that TOFD has better sizing capabilities than other techniques. I would not say it is a limitation.

I do agree with the use of other pulse-echo techniques when performing TOFD. You do have a "blind" zone in the upper cap of the weld that may mask defects. This limitation can be more extreme if the diameter of the object under test is small. There also may be limitations with the I.D. area of the weld. This too can be solved using a pulse-echo technique to provide coverage in these areas. I would suggest a mechanized Automated Ultrasonic Inspection using TOFD for the entire weld volume, backing that up with a couple of 45 degree shearwave transducers which are focussed on each side of the O.D. cap, and a 60 degree Shearwave transducer focussed at the root.

You may also want to think of Phased Array. Phased Array is another Ultrasonic technique that provides encoded imaging and can provide volumetric coverage of the entire weld. If you would like further information, please contact me at any time.



 
06:29 Mar-14-2005
Jim Knowles
Re: TOFD I agree with James Gauthier TOFD is a great tool when used correctly and with the provision to include Pulse Echo as another method to confirm your findings. Limitations are, near surface indications close to or within the lateral wave, which may cover the diffraction indication, but most TOFD software has the facility for "Lateral Wave removal" which may aid or uncover the indication. Also look within the shear component for a repeat or indications.

: TOFD is a great tool for weld inspection. I agree with the comment that TOFD requires experience and training with regards to analysis, however I don't think I have ever discussed sizing limitations with anyone. One of the advantages is that TOFD has better sizing capabilities than other techniques. I would not say it is a limitation.
: I do agree with the use of other pulse-echo techniques when performing TOFD. You do have a "blind" zone in the upper cap of the weld that may mask defects. This limitation can be more extreme if the diameter of the object under test is small. There also may be limitations with the I.D. area of the weld. This too can be solved using a pulse-echo technique to provide coverage in these areas. I would suggest a mechanized Automated Ultrasonic Inspection using TOFD for the entire weld volume, backing that up with a couple of 45 degree shearwave transducers which are focussed on each side of the O.D. cap, and a 60 degree Shearwave transducer focussed at the root.
: You may also want to think of Phased Array. Phased Array is another Ultrasonic technique that provides encoded imaging and can provide volumetric coverage of the entire weld. If you would like further information, please contact me at any time.
------------ End Original Message ------------




 
07:17 Mar-14-2005

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1197
Re: TOFD TOFD, like other NDT methods, has its pros and cons. Everyone seems to now know about the lateral wave dead zone issue. The spatial resolution and backwall dead zones are apparently less well understood. I recall a company claiming to be able to use TOFD to size, and assess for backwall interaction if not surface connected, flaws to 0.3mm high in 38mm wall butt welds. The flaws them selves are not separable from the backwall under most TOFD conditions, never mind trying to determine if surface breaking or not!

A good reference for understanding and quantifying the limitations of TOFD can be found in EN-583-6. Par. 10.1.5 and 10.2 provide equations that will be informative to quantify the limits. I have checked them against the field results and the equations provide values that are VERY close to the values obtained from the scan data.

Under some conditions it may be seen that pulse-echo tip diffraction provides better resolution than TOFD. Pulse-echo has the advantage that the depth resolution is a constant for all depths whereas TOFD has increasing resolution with increasing depth.

As James Gauthier noted, TOFD is a tool, but there may be other tools in yout UT toolbox. Find the one that works the best for the problem at hand.

----------- Start Original Message -----------
: I agree with James Gauthier TOFD is a great tool when used correctly and with the provision to include Pulse Echo as another method to confirm your findings. Limitations are, near surface indications close to or within the lateral wave, which may cover the diffraction indication, but most TOFD software has the facility for "Lateral Wave removal" which may aid or uncover the indication. Also look within the shear component for a repeat or indications.
: : TOFD is a great tool for weld inspection. I agree with the comment that TOFD requires experience and training with regards to analysis, however I don't think I have ever discussed sizing limitations with anyone. One of the advantages is that TOFD has better sizing capabilities than other techniques. I would not say it is a limitation.
: : I do agree with the use of other pulse-echo techniques when performing TOFD. You do have a "blind" zone in the upper cap of the weld that may mask defects. This limitation can be more extreme if the diameter of the object under test is small. There also may be limitations with the I.D. area of the weld. This too can be solved using a pulse-echo technique to provide coverage in these areas. I would suggest a mechanized Automated Ultrasonic Inspection using TOFD for the entire weld volume, backing that up with a couple of 45 degree shearwave transducers which are focussed on each side of the O.D. cap, and a 60 degree Shearwave transducer focussed at the root.
: : You may also want to think of Phased Array. Phased Array is another Ultrasonic technique that provides encoded imaging and can provide volumetric coverage of the entire weld. If you would like further information, please contact me at any time.
------------ End Original Message ------------




 
08:05 Mar-15-2005

S S Ananthan

Consultant,
RAA Tech Solutions,
India,
Joined Jun 2000
36
Re: TOFD ----------- Start Original Message -----------
: : Dear Friends,
: : I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: : Thanks
: : S S Ananthan
: Is your requirement coming from a need to use Co 60 on this thickness?
: If so have you considered using Computed RT using Iridium? Now accepted by ASME Code Case.
------------ End Original Message ------------

Dear Mr. Dent McIntyre,

What is Computed RT using Ir 192 for a thickness of 120 mm ? Can you pl elaborate ?

S S Ananthan



 
02:39 Mar-15-2005

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
246
Re: TOFD ----------- Start Original Message -----------
: : : Dear Friends,
: : : I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: : : Thanks
: : : S S Ananthan
: : Is your requirement coming from a need to use Co 60 on this thickness?
: : If so have you considered using Computed RT using Iridium? Now accepted by ASME Code Case.
: Dear Mr. Dent McIntyre,
: What is Computed RT using Ir 192 for a thickness of 120 mm ? Can you pl elaborate ?
: S S Ananthan


Exposure times might be long but it can be done. With 100 Ci and 15" SPD exposure time is about 6 hours.

Dent

------------ End Original Message ------------





 
08:40 Mar-16-2005

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
174
Re: TOFD In addition to the reply by Ed Ginzel I want to add some more information on the use of TOFD.

In February 2005 a new European Technical Specification has been published on TOFD:

CEN/TS 14751
Welding - Use of time-of-flight diffraction technique (TOFD) for examination of welds
(available also in French and German language).

Based on European Standard ENV 583-6 the new TS gives guidance on the specific capabilites and limitations of TOFD for the detection, location, sizing and characterization of dicontinuities in fusion welded joints.
Four examination classes are defined.
A table for recommended probe-set-ups is included for the thickness range from 6 mm up to 300 mm (steel).
With a lot of TOFD-images the correct and inappropriate use of TOFD is illustrated.

Some personal remarks:
TOFD imaging is based on diffracted signals from discontinuities. These signals in general are more than 26 dB weaker (factor 1/20) than reflected signals. Therefore the application of TOFD needs a material where scattering from the grain structure is much lesser than the diffracted signals, e.g. with fine-grained steel.
Cracks open to surface which act like retro-reflectors give a signal which is more than 30 dB better than diffracted ones. So with reflected signals in general you get much higher signal-to-noise ratio than with TOFD.
Therefore TOFD cannot replace all well known detection techniques on welds.

Kind regards
Udo Schlengermann
GE Inspection Technologies GmbH, Huerth, Germany

----------- Start Original Message -----------
: TOFD, like other NDT methods, has its pros and cons. Everyone seems to now know about the lateral wave dead zone issue. The spatial resolution and backwall dead zones are apparently less well understood. I recall a company claiming to be able to use TOFD to size, and assess for backwall interaction if not surface connected, flaws to 0.3mm high in 38mm wall butt welds. The flaws them selves are not separable from the backwall under most TOFD conditions, never mind trying to determine if surface breaking or not!
: A good reference for understanding and quantifying the limitations of TOFD can be found in EN-583-6. Par. 10.1.5 and 10.2 provide equations that will be informative to quantify the limits. I have checked them against the field results and the equations provide values that are VERY close to the values obtained from the scan data.
: Under some conditions it may be seen that pulse-echo tip diffraction provides better resolution than TOFD. Pulse-echo has the advantage that the depth resolution is a constant for all depths whereas TOFD has increasing resolution with increasing depth.
: As James Gauthier noted, TOFD is a tool, but there may be other tools in yout UT toolbox. Find the one that works the best for the problem at hand.
:
: : I agree with James Gauthier TOFD is a great tool when used correctly and with the provision to include Pulse Echo as another method to confirm your findings. Limitations are, near surface indications close to or within the lateral wave, which may cover the diffraction indication, but most TOFD software has the facility for "Lateral Wave removal" which may aid or uncover the indication. Also look within the shear component for a repeat or indications.
: : : TOFD is a great tool for weld inspection. I agree with the comment that TOFD requires experience and training with regards to analysis, however I don't think I have ever discussed sizing limitations with anyone. One of the advantages is that TOFD has better sizing capabilities than other techniques. I would not say it is a limitation.
: : : I do agree with the use of other pulse-echo techniques when performing TOFD. You do have a "blind" zone in the upper cap of the weld that may mask defects. This limitation can be more extreme if the diameter of the object under test is small. There also may be limitations with the I.D. area of the weld. This too can be solved using a pulse-echo technique to provide coverage in these areas. I would suggest a mechanized Automated Ultrasonic Inspection using TOFD for the entire weld volume, backing that up with a couple of 45 degree shearwave transducers which are focussed on each side of the O.D. cap, and a 60 degree Shearwave transducer focussed at the root.
: : : You may also want to think of Phased Array. Phased Array is another Ultrasonic technique that provides encoded imaging and can provide volumetric coverage of the entire weld. If you would like further information, please contact me at any time.
------------ End Original Message ------------




 
00:05 Mar-18-2005

Pramod Myakal

Consultant
AGM Techno consultants,
India,
Joined Jan 2003
22
Re: TOFD Dear Sir,

We offer Advance NDT inspection services in India. TOFD services also, for details pl revert this mail to mic_ndt@yahoo.com

Thanks


----------- Start Original Message -----------
: : : Dear Friends,
: : : I have a requirement to replace RT for 120 mm thick plate weld for structural applications with another NDT method. I have heard of TOFD. Can it replace RT in such a case ? Any experience on this ?
: : : Thanks
: : : S S Ananthan
: : Is your requirement coming from a need to use Co 60 on this thickness?
: : If so have you considered using Computed RT using Iridium? Now accepted by ASME Code Case.
: Dear Mr. Dent McIntyre,
: What is Computed RT using Ir 192 for a thickness of 120 mm ? Can you pl elaborate ?
: S S Ananthan
------------ End Original Message ------------




 
06:26 Mar-20-2005

mohd

Engineering
Universiti Kebangsaan Malaysia,,
Malaysia,
Joined Jan 2001
5
Re: TOFD I agree on all the comment.
In fact i've been using TOFD for several years already. It works well on thick material but having said that the operator has to know the pros & cons of the equipment & its capibility. The easiest way to do it is counter check any reportable flaw by TOFD using normal UT FLaw.
Rgds
TOFD Operator

----------- Start Original Message -----------
: In addition to the reply by Ed Ginzel I want to add some more information on the use of TOFD.
: In February 2005 a new European Technical Specification has been published on TOFD:
: CEN/TS 14751
: Welding - Use of time-of-flight diffraction technique (TOFD) for examination of welds
: (available also in French and German language).
: Based on European Standard ENV 583-6 the new TS gives guidance on the specific capabilites and limitations of TOFD for the detection, location, sizing and characterization of dicontinuities in fusion welded joints.
: Four examination classes are defined.
: A table for recommended probe-set-ups is included for the thickness range from 6 mm up to 300 mm (steel).
: With a lot of TOFD-images the correct and inappropriate use of TOFD is illustrated.
: Some personal remarks:
: TOFD imaging is based on diffracted signals from discontinuities. These signals in general are more than 26 dB weaker (factor 1/20) than reflected signals. Therefore the application of TOFD needs a material where scattering from the grain structure is much lesser than the diffracted signals, e.g. with fine-grained steel.
: Cracks open to surface which act like retro-reflectors give a signal which is more than 30 dB better than diffracted ones. So with reflected signals in general you get much higher signal-to-noise ratio than with TOFD.
: Therefore TOFD cannot replace all well known detection techniques on welds.
: Kind regards
: Udo Schlengermann
: GE Inspection Technologies GmbH, Huerth, Germany
: : TOFD, like other NDT methods, has its pros and cons. Everyone seems to now know about the lateral wave dead zone issue. The spatial resolution and backwall dead zones are apparently less well understood. I recall a company claiming to be able to use TOFD to size, and assess for backwall interaction if not surface connected, flaws to 0.3mm high in 38mm wall butt welds. The flaws them selves are not separable from the backwall under most TOFD conditions, never mind trying to determine if surface breaking or not!
: : A good reference for understanding and quantifying the limitations of TOFD can be found in EN-583-6. Par. 10.1.5 and 10.2 provide equations that will be informative to quantify the limits. I have checked them against the field results and the equations provide values that are VERY close to the values obtained from the scan data.
: : Under some conditions it may be seen that pulse-echo tip diffraction provides better resolution than TOFD. Pulse-echo has the advantage that the depth resolution is a constant for all depths whereas TOFD has increasing resolution with increasing depth.
: : As James Gauthier noted, TOFD is a tool, but there may be other tools in yout UT toolbox. Find the one that works the best for the problem at hand.
: :
: : : I agree with James Gauthier TOFD is a great tool when used correctly and with the provision to include Pulse Echo as another method to confirm your findings. Limitations are, near surface indications close to or within the lateral wave, which may cover the diffraction indication, but most TOFD software has the facility for "Lateral Wave removal" which may aid or uncover the indication. Also look within the shear component for a repeat or indications.
: : : : TOFD is a great tool for weld inspection. I agree with the comment that TOFD requires experience and training with regards to analysis, however I don't think I have ever discussed sizing limitations with anyone. One of the advantages is that TOFD has better sizing capabilities than other techniques. I would not say it is a limitation.
: : : : I do agree with the use of other pulse-echo techniques when performing TOFD. You do have a "blind" zone in the upper cap of the weld that may mask defects. This limitation can be more extreme if the diameter of the object under test is small. There also may be limitations with the I.D. area of the weld. This too can be solved using a pulse-echo technique to provide coverage in these areas. I would suggest a mechanized Automated Ultrasonic Inspection using TOFD for the entire weld volume, backing that up with a couple of 45 degree shearwave transducers which are focussed on each side of the O.D. cap, and a 60 degree Shearwave transducer focussed at the root.
: : : : You may also want to think of Phased Array. Phased Array is another Ultrasonic technique that provides encoded imaging and can provide volumetric coverage of the entire weld. If you would like further information, please contact me at any time.
------------ End Original Message ------------




 


© NDT.net - The Web's Largest Portal of Nondestructive Testing (NDT) ISSN 1435-4934

Open Access Database, |Conference Proceedings| |Articles| |News| |Exhibition| |Forum| |Professional Network|