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Technical Discussions
Cesar Tovar
NDT Inspector, Quality assurance Representative
Toronto Transit Commission, Mexico, Joined Sep 2014, 7

Cesar Tovar

NDT Inspector, Quality assurance Representative
Toronto Transit Commission,
Mexico,
Joined Sep 2014
7
19:47 Oct-19-2018
How to validate a PAUT test within the AWS D1.1?
Download Virus Scan recommended!

I have been hearing several ways to use the PAUT technique, in order to validate the AWS D1.1 code...
An expert said that, using the phasor XS and calibrate sensitivity with 55° can apply the code directly...using the table 6.3......this must be a joke.... How he can compare the sensitivity using 55° and validate with 70°. someone who can explain this?
Please take a look to the attached.

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

J Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
22:25 Oct-19-2018
Re: How to validate a PAUT test within the AWS D1.1?
In Reply to Cesar Tovar at 19:47 Oct-19-2018 (Opening).

Cesar

Paragraphs 6.34 and 6.35 in the 2015 D1.1 Code provide requirements for PAUT and TOFD. If Phased Array is used, then what would be the acceptance criteria. Well, you would need to use the sector scan to find the flaw and then rate it per the 70, 60 or 45 degree beam per the tables. Or, you could use Annex S which allows for DAC/TCG, if the engineer approves it.

I developed the Phased Array Annex K for AWS D1.5 2015 Code. In Annex K is a procedure for Phased Array with an Acceptance Criteria which basically follows old "Annex S", fom back in the 80s).

I just returned today from the AWS Code Meetings in Colorado. Phased Array for D1.1 will hit the 2020 AWS Code.

To answer your question, there is no way to accept or reject a flaw per the tables unless it is a 70, 60 or a 45 beam in accordance with the table.

Mark Davis
ASNT UT Level III
Founder of the University of Ultrasonics



2    
 
 
Cesar
NDT Inspector, Quality assurance Representative
Toronto Transit Commission, Mexico, Joined Sep 2014, 7

Cesar

NDT Inspector, Quality assurance Representative
Toronto Transit Commission,
Mexico,
Joined Sep 2014
7
01:54 Oct-21-2018
Re: How to validate a PAUT test within the AWS D1.1?
In Reply to J Mark Davis at 22:25 Oct-19-2018 .

Hi J. Mark, thank you for your reply, here the question/issue is this:
Is it valid to calibrate sensitivity with 55° and change the angle with the knob to 70° and accept whatever they find...?
I´m going to get the Annex K for D1.5 and check the information...thank you so much!

    
 
 
Paul Holloway
Consultant, UT Level 3
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 169

Paul Holloway

Consultant, UT Level 3
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
169
17:13 Oct-21-2018
Re: How to validate a PAUT test within the AWS D1.1?
In Reply to Cesar Tovar at 19:47 Oct-19-2018 (Opening).

zoom image


Attenuation at 60deg for AWS search unit

Hi Cesar,

Would like to chime in with a couple things here. Much of this you may already know but perhaps it will be of some benefit to others.

First off, the expert you quoted is definitely incorrect. The AWS D1.1 code and the acceptance tables 6.2 and 6.3 are based on indication ratings with calculated (not measured) attenuation. The assumption is an attenuation of 2 dB/in, which is more or less correct if the search unit parameters remain within the strict limits in 6.21.7, and attenuation is averaged over extremely long sound paths (~ 400 mm). This is illustrated in the attached image for 60 degrees from a paper presented at the 2017 NDT in Canada Conference. The calculated attenuation at 55 degrees will be less than at 70 degrees, simply due to the difference in sound path. Right off the bat, the assumption that picking a median angle like 55 degrees and applying the result across all angles is simply wrong.

Secondly, the echo amplitude at 55 degrees will be different than at 70 degrees. The original AWS D1.1 tables were developed in 1969, and were based on the assumption that 70 degrees would be the most desirable angle. There are arguments against this, and few if any other codes in the world favour 70 degrees. Each angle (45, 60 and 70) has different acceptance levels, so you can't apply one to the other. Earlier this year, the Canadian code CSA W59 addressed this by the addition of Annex X, permitting manual UT and manual PAUT and calibration with a DAC/TCG, and issued adapted acceptance tables that held to the same quality levels but *without* angle dependence. Clause 8.2 in the W59 code remains relatively unscathed, so those that want to stick to the old ways can do so for the time being.

Mark Davis is correct... you must evaluate at 45, 60 or 70 degrees. Adding to the complication is that the acceptance tables 6.2 and 6.3 are angle dependent. The lower angles (45 and 60) do not apply unless you get into relatively thick welds. All welds 1.5" or less have only a 70 degree column, so without columns for 45 and 60 you have no choice. This is regardless of weld type and bevel geometry.

These limitations were major driving factors to recent changes in CSA W59 for 2018.

Hope this helps,
Paul
3    
 
 
Rick Cahill
Rick Cahill
09:56 Oct-22-2018
Re: How to validate a PAUT test within the AWS D1.1?
In Reply to Cesar Tovar at 19:47 Oct-19-2018 (Opening).

Mark and Paul's responses are well stated and correct. Also, it is important to remember that the probe's acoustic aperture is critical too. The virtual probe aperture that is created with the phased array probe must comply with the AWS standard otherwise the amplitudes that are recorded will not be a one-to-one comparison to the standard.

    
 
 

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