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Technical Discussions
Rene
El Salvador, Joined Apr 2019, 2

Rene

El Salvador,
Joined Apr 2019
2
01:05 Apr-06-2019
DAC calibration using curved Block

Hi guys

I have a question

For UT shear wave weld inspection of butt weld on 2'' diameter piping, i can use basic calibration block given in ASME ,Figure T-434.3-2 for DAC curve, right? i will use the same material specification group P1.
Later, do a i need the dac offset curve al 6db and 12db for rejection criteria? or with the principal curve dac is enough?

thanks

    
 
 
Paul Holloway
Consultant, UT Level 3
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 171

Paul Holloway

Consultant, UT Level 3
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
171
22:21 Apr-06-2019
Re: DAC calibration using curved Block
In Reply to Rene at 01:05 Apr-06-2019 (Opening).

Hi Rene:

Yes, absolutely you can use the alternative block shown in Fig. T-434.3-2. You will need to generate a DAC/TCG, and then add 6dB of scanning gain as per T-471.4.1.

The rejection level (re: your 6dB or 12dB offset from reference) will depend on the code that you are inspecting to. If they are ASME B31.3 (process piping) welds, then the rejection level is actually the reference level (i.e. unless the indication breaks DAC, ignore it).

1    
 
 
Rene
El Salvador, Joined Apr 2019, 2

Rene

El Salvador,
Joined Apr 2019
2
03:48 Apr-07-2019
Re: DAC calibration using curved Block
In Reply to Paul Holloway at 22:21 Apr-06-2019 .

Thanks Paul,

I will examine a 1/4" thick overheating pipe, can i generate the DAC curve only with a 1mm side drill hole at half the thickness as reference level?

    
 
 
Paul Holloway
Consultant, UT Level 3
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 171

Paul Holloway

Consultant, UT Level 3
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
171
10:39 Apr-07-2019
Re: DAC calibration using curved Block
In Reply to Rene at 03:48 Apr-07-2019 .

Unfortunately you won't be able to use a SDH. ASME states that the hole must be 38mm (1.5“) long and you simply won't be able to drill that on a 2" OD and 1/4" thick pipe. There's not enough material.

    
 
 

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