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- since 1996 -
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Technical Discussions
Sungeun, Joo
R & D, UT
Prognosis Diagnosis Team, South Korea, Joined Jun 2013, 11

Sungeun, Joo

R & D, UT
Prognosis Diagnosis Team,
South Korea,
Joined Jun 2013
11
11:04 Jun-18-2013
PAUT calibration(esp. TCG)

Hi, there

In case of testing the pipes using PAUT.

I think it's impossible to draw the TCG on the pipe, so I using the plate.
Is it alright? and if need a compensation, how can i compensate?

If you have any idea for drawing the TCG(on pipe), please give me a any inform.

Thanks a lot.

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
14:42 Jun-18-2013
Re: PAUT calibration(esp. TCG)
In Reply to Sungeun, Joo at 11:04 Jun-18-2013 (Opening).

Sungeun, there has been similar discussion on a different thread, See http://www.ndt.net/forum/thread.php?admin=&forenID=0&msgID=46949&rootID=43819#46949
If you can make a block with a curved surface to match the pipe you are testing and use side drilled holes you should be able to demonstrate equal or greater sensitivity than that afforded by the notches. Difficulties arise when you try changing the wedge from flat (for the TCG calibration on the plate) to curved (for scanning on the pipe).

 
 Reply 
 
Sungeun, Joo
R & D, UT
Prognosis Diagnosis Team, South Korea, Joined Jun 2013, 11

Sungeun, Joo

R & D, UT
Prognosis Diagnosis Team,
South Korea,
Joined Jun 2013
11
02:35 Jun-19-2013
Re: PAUT calibration(esp. TCG)
In Reply to Ed Ginzel at 14:42 Jun-18-2013 .

Dear. Ed Ginzel

Thanks for your kindness reply.
and also I checked your previous answer.

but, still I don't know whether I understand you or not,

how can I compensate two different wedges(Between Flat wedge for the TCG calibration on the plate and Curved wedge for scanning on the pipe).

Sorry to disturb you,but I really wonder about that.
Thanks.

 
 Reply 
 
Swadesh Singh
Saudi Arabia, Joined May 2012, 60

Swadesh Singh

Saudi Arabia,
Joined May 2012
60
08:42 Jun-19-2013
Re: PAUT calibration(esp. TCG)
In Reply to Ed Ginzel at 14:42 Jun-18-2013 .

Hello Mr. Ed,

I agree that SDH gives higher sensitivity than notches, since SDH's are omnidirectional reflectors whereas notches are highly dependent on angles(sometimes i have experienced it's really a tough task to draw a TCG using notches especially for higher angles around 70 deg).

But, i wonder then why ASME code states to use notches for pipes and SDH's for plates.

Is there any technical explanation for it?

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
13:34 Jun-19-2013
Re: PAUT calibration(esp. TCG)
In Reply to Swadesh Singh at 08:42 Jun-19-2013 .

Swadesh, I think there is a distinct advantage in making a simple and repeatable target in a section of pipe having the same dimensions and material as that being tested. The notch is especially convenient for pipe since SDHs are not easily put into them (and for small diameters it is not possible to make a SDH that is long enough).
For a single element probe, as we use in manual UT, there was less of an issue because the DAC has you compare the response of the same angle at different soundpaths on the notch. But for a sectorial scan, construction of a TCG does 2 things...it equalises the response along the soundpath, but it also attempts to equalise the response of every angle as well.
I suspect that the ASME requirement was reasonable when we used single element probes with manual UT. It has been the introduction of the sectorial scan that has cause the issues we are now discussing.

 
 Reply 
 
Mrinal Maity
NDT Inspector,
Sigma Inspection pvt ltd ., India, Joined Oct 2014, 2

Mrinal Maity

NDT Inspector,
Sigma Inspection pvt ltd .,
India,
Joined Oct 2014
2
18:39 Jun-05-2017
Re: PAUT calibration(esp. TCG)
In Reply to Ed Ginzel at 13:34 Jun-19-2013 .

Dear Ginzel sir..
Our job 6 inch 21.44(AS) mm.For wedge delay calibration what block we used..IIW V1/ same diameter& thick . Notch block. plz discuss this topic.

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
14:58 Jun-10-2017
Re: PAUT calibration(esp. TCG)
In Reply to Mrinal Maity at 18:39 Jun-05-2017 .

Mrinal, wedge delay calibration for a phased-array setup is what is used to calculate the correction in time to correctly position an indication in the test material. You only need a target of a known fixed depth in the material tested (e.g. a SDH) and the intent is then to maximise the signal from each delay-law pulse and use trigonometry to calculate the distance in the material with a pre-determined acoustic velocity. It can get a bit tricky with the math being used because the incident point in the wedge is changing (both incident angle and point of impingement). The ultrasound instrument is using units of time so it must apportion some of the time to the travel in the wedge and some in the tested material. If you have correctly entered the velocity of the test material and wedge material, the computation of the distance in the test material for a specified angle can be calculated and this is subtracted from the total time that the pulse is clocked at from the time zero of the initial pulse. When done correctly for an S-scan the compensation for wedge time makes the displayed position of the SDH correct for all angles used.
Because a notch can result in the maximum response occurring at an angle other than the refracted angle that connects to the corner, it should not be used for wedge delay.

 
 Reply 
 

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