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Technical Discussions
Rolf Diederichs
Director,
NDT.net, Germany, Joined Nov 1998, 608

Rolf Diederichs

Director,
NDT.net,
Germany,
Joined Nov 1998
608
03:11 Sep-29-1999
How many Probes TOFD uses?

In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
The correct answer should be "2".
However, one quiz participant wrote to us
"In the question 6 i'm not agree.....
I'm Using TOFD with 1 transducer...".

Is that possible?

Rolf Diederichs



    
 
 Reply 
 
Robert (Rocky) A. Day
Engineering
Milky Way Jewels, USA, Joined Nov 1998, 40

Robert (Rocky) A. Day

Engineering
Milky Way Jewels,
USA,
Joined Nov 1998
40
00:29 Sep-30-1999
Re: How many Probes TOFD uses?
Yes any number of probes may be used in TOFD. The geometry of the diffraction can be arranged to allow using one probe pulse echo, so that a second probe can be avoided. One probe is usually smaller and easier to use. Some types of part/crack geometries may not allow this which is a disadvantage in those cases. It is really a good idea to do diffraction calculations to determine the best geometry to use when not employing one of the 'canned' applications. My address and phone numbers have changed.

Regards,
Robert (Rocky) A. Day
220 Gates Street
San Francisco, CA 94110
(415) 647-0625
Fax: (415) 641-4947

: In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: The correct answer should be "2".
: However, one quiz participant wrote to us
: "In the question 6 i'm not agree.....
: I'm Using TOFD with 1 transducer...".

: Is that possible?

: Rolf Diederichs




    
 
 Reply 
 
Robert (Rocky) A. Day
Engineering
Milky Way Jewels, USA, Joined Nov 1998, 40

Robert (Rocky) A. Day

Engineering
Milky Way Jewels,
USA,
Joined Nov 1998
40
00:34 Sep-30-1999
Re: How many Probes TOFD uses?
Yes you can do TOFD with one probe in pulse-echo. It is my impression that this is the most common application. You can have diffraction in forward and backward directions in most situations. Diffraction calculations can be a good idea to get an idea of the optimum order and direction to use.

: In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: The correct answer should be "2".
: However, one quiz participant wrote to us
: "In the question 6 i'm not agree.....
: I'm Using TOFD with 1 transducer...".

: Is that possible?

: Rolf Diederichs




    
 
 Reply 
 
Jan Verkooijen
Director,
Sonovation, Netherlands, Joined Nov 1998, 29

Jan Verkooijen

Director,
Sonovation,
Netherlands,
Joined Nov 1998
29
07:05 Sep-30-1999
Re: How many Probes TOFD uses?
You are absolutely right in saying that in many cases you will have forward and backward scattered
diffraction signals, and therefore you could use 1, 2 or many probes to capture the diffraction
signal. However, in industry the general consensus is that with 1 probe it is referred to as
"tip-diffraction" of "back-scattering", whereas TOFD is the method using two probes in a through
transmission mode. This definition is also used in the two main standards on TOFD, prEN 583 pt 6
and BS 7706, where also a reference set up is indicated with two probes in through transmission,
or if you like forward scattering mode. Therefore I think Rolf has rightly made the two probe
answer the correct one.

Jan Verkooijen


: Yes you can do TOFD with one probe in pulse-echo. It is my impression that this is the most common application. You can have diffraction in forward and backward directions in most situations. Diffraction calculations can be a good idea to get an idea of the optimum order anddirection to use.

: : In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: : The correct answer should be "2".
: : However, one quiz participant wrote to us
: : "In the question 6 i'm not agree.....
: : I'm Using TOFD with 1 transducer...".

: : Is that possible?

: : Rolf Diederichs




    
 
 Reply 
 
Jairo Humberto Guzman
NDT Inspector, NDT researcher
Ecopetrol ICP, Colombia, Joined Nov 1998, 6

Jairo Humberto Guzman

NDT Inspector, NDT researcher
Ecopetrol ICP,
Colombia,
Joined Nov 1998
6
07:59 Sep-30-1999
Re: How many Probes TOFD uses?
: In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: The correct answer should be "2".
: However, one quiz participant wrote to us
: "In the question 6 i'm not agree.....
: I'm Using TOFD with 1 transducer...".

: Is that possible?

: Rolf Diederichs

You can use one probe for TOFD and a good the standard will tell you wich is the eco pulse and the difracted wave.
Some times the material does not permit to diferenciate the two signals so you have to use two or more probes.



    
 
 Reply 
 
Robert (Rocky) A. Day
Engineering
Milky Way Jewels, USA, Joined Nov 1998, 40

Robert (Rocky) A. Day

Engineering
Milky Way Jewels,
USA,
Joined Nov 1998
40
06:59 Oct-01-1999
Re: How many Probes TOFD uses?
Thanks, I am unfamiliar with these standards. There does seem to be some differences in terminology over here (US) as TOFD is usually used to refer to one transducer 'tip-diffraction' methods. More correctly 'back-scattered,' although both terms are unclear as to the number of transducers. So I suspect all the US quiz takers would have missed this question not having much contact with EU standards. Maybe we need more alphabetic abbreviations? No, No, I didn't say that!

: You are absolutely right in saying that in many cases you will have forward and backward scattered
: diffraction signals, and therefore you could use 1, 2 or many probes to capture the diffraction
: signal. However, in industry the general consensus is that with 1 probe it is referred to as
: "tip-diffraction" of "back-scattering", whereas TOFD is the method using two probes in a through
: transmission mode. This definition is also used in the two main standards on TOFD, prEN 583 pt 6
: and BS 7706, where also a referenceset up is indicated with two probes in through transmission,
: or if you like forward scattering mode. Therefore I think Rolf has rightly made the two probe
: answer the correct one.

: Jan Verkooijen

:
: : Yes you can do TOFD with one probe in pulse-echo. It is my impression that this is the most common application. You can have diffraction in forward and backward directions in most situations. Diffraction calculations can be a good idea to get an idea of the optimum order and direction to use.

: : : In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: : : The correct answer should be "2".
: : : However, one quiz participant wrote to us
: : : "In the question 6 i'm not agree.....
: : : I'm Using TOFD with 1 transducer...".

: : : Is that possible?

: : : Rolf Diederichs




    
 
 Reply 
 
Mark Davis
Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama, USA, Joined Mar 2000, 85

Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
00:14 Dec-02-1999
Re: How many Probes TOFD uses?
: In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: The correct answer should be "2".
: However, one quiz participant wrote to us
: "In the question 6 i'm not agree.....
: I'm Using TOFD with 1 transducer...".

: Is that possible?

: Rolf Diederichs





    
 
 Reply 
 
Mark Davis
Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama, USA, Joined Mar 2000, 85

Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
00:15 Dec-02-1999
Re: How many Probes TOFD uses?
: In question 6 of the TOFD Quiz we asked "How many Probes TOFD uses?"
: The correct answer should be "2".
:

You can use one for a backscatter technique or use two in forward scatter or pitch catch mode.



    
 
 Reply 
 
JOAO JAYME IESS
JOAO JAYME IESS
05:34 Jan-15-2001
Re.: CERAMIC PROBES FOR CEMENT KILNS
My is Joao Jayme Iess, technical manager for VOTORANTIM CIMENTOS, in Brasil. We are deeply interested to know companies that manufacture ceramic probes for utilizatin into cement kilns.


    
 
 Reply 
 
JOAO JAYME IESS
JOAO JAYME IESS
05:34 Jan-15-2001
Re: Re.: CERAMIC PROBES FOR CEMENT KILNS
: My is Joao Jayme Iess, technical manager for VOTORANTIM CIMENTOS, in Brasil. We are deeply interested to know companies that manufacture ceramic probes for utilizatin into cement kilns.





    
 
 Reply 
 

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