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Technical Discussions
Peter
Singapore, Joined Jan 2012, 122

Peter

Singapore,
Joined Jan 2012
122
09:00 Nov-03-2014
SELECTION OF REFERENCE HOLE-ASME
zoom image



Dear Experts,


In accordance with ASME SECTION V, 20” and above shall use basic calibration block for sensitivity settings. It’s clearly stated that 38mm reference block can cover up to 50mm weld thickness. Our usual practice to choose first hole for sensitivity setting will be 1/4t. t is the thickness of the base metal of the weldment that we planned to inspect. For example:-


DAC Block 38mm.


a) Nominal thickness = 30mm
1/4t = 7.5mm so I can choose 9.5mm side drill hole in the block

b) Nominal Thickness = 48mm
1/4t = 12mm so I can choose 19mm side drill hole in the block



1. Am I selecting the reference sensitivity holes correctly?
2. Why we are choosing sensitivity based on 1/4t? Any explanation?
3. Can I apply the same for phased array inspection?


Help me on this matter. Thanks in advance.


Peter.





 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 869

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
869
13:39 Nov-03-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Peter at 09:00 Nov-03-2014 (Opening).

Peter,

The sensitivity of your inspection is not based on 1/4 T. It is based on the thickness of your weld. If you look at Fig. T-434.2.1, it tells you that for material thickness up to 1 inch (25mm); the hole diameter on your block shall be 3/32 inches (2.5mm); between 1 and 2 inches (25-50mm) it shall be 1/8 inches (3mm) and so on.

The holes location (1/4 T and 1/2 T) have been selected to allow you to make your DAC curve. After setting the amplitude of your holes (1/4 and 1/2 T), your turn your block over and will obtain your amplitude for the 3/4 T beam path. This way, you will obtain a three point DAC curve.

 
 Reply 
 
John
John
20:52 Nov-03-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Peter at 09:00 Nov-03-2014 (Opening).

Someone is after the ever elusive 1 point DAC

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
23:32 Nov-03-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Peter at 09:00 Nov-03-2014 (Opening).

zoom image

MUT Scanplan

Peter,
Selection of first SDH in the reference block depends on your scan plan and weld geometry.for example if 70 degree probe close to the weld cap it can scan the weld body at minimum thickness of weld metal in half skip.In the picture that is attached to this post you :
D= depth of first SDH in reference block to make DAC.
d= minimum depth of weld metal that is possible to scan by angle beam probes.
There is some thump rules:
1.D ≤ d
2.d 70 degree probe < d 60 degree probe < d 45 degree probe.
finally you choose optimum SDH on reference block to draw DAC.
you can apply same method to do the TCG calibration for Phased array.But depth of last SDH for TCG is equal or more than 2 times(when scan plan cover the weld volume plus HAZ at Full skip or leg II) or more than 3 times( Leg III if you are using) of Weld metal thickness.

 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 869

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
869
23:35 Nov-03-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Ali at 23:32 Nov-03-2014 .

Ali my friend,

You have to work to code!!!!

 
 Reply 
 
Peter
Singapore, Joined Jan 2012, 122

Peter

Singapore,
Joined Jan 2012
122
02:57 Nov-04-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Michel Couture at 23:35 Nov-03-2014 .

Hi Michel,


Thanks for the advice. Actually i am not doing 1 point DAC and would like to know the first side drill hole to set the sensitivity. The selection of first side drill hole is important. Using a DAC block 38mmand setting a sensitivity on first 1/4t hole located at 9.5mm and second side 1/2t side drill hole located at 19mm is totally different. Sensitivity setting on 19mm side drill hole is hire compare with 9.5mm.I am posting this to understand whether am i selecting a correct first side drill hole for sensitivity settings or not.

Peter

 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 869

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
869
14:21 Nov-04-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Peter at 02:57 Nov-04-2014 .

Peter,

I don't see what your problem is. ThacASME code is pretty straight forward when it comes to making a calibration block. I think your problem is that you don't know how to do a DAC! Is this possible?

 
 Reply 
 
Dent
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 250

Dent

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
250
15:00 Nov-04-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Michel Couture at 14:21 Nov-04-2014 .

If you read ASME Sect V Article 4 Par T463.1.2 it tells you to use the hole that provides the maximum response in the area of interest

 
 Reply 
 
Peter
Singapore, Joined Jan 2012, 122

Peter

Singapore,
Joined Jan 2012
122
05:29 Nov-05-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Dent at 15:00 Nov-04-2014 .

Hi Michel,


I dont have any single problem plotting DAC. My question is the selection of first hole for reference sensitivity. Let me put in this way. For example i am using DAC block 38mm where the holes located at stated below. I set my first DAC point on 1/4t and followed by 1/2t and 3/4t and if possible the forth point at fullskip distance. With this DAC curve am i able to detect all indication for thickness between 25mm up to 50mm as stated in ASME ? If select 9.5mm side drill hole as by first reference point, am i able to detect a toe crack located at fullskip distance for 50mm thickness material?




1. 1/4 t = 9.5mm
2. 1/2t = 38mm
3. 3/4t = 28.5mm

Peter

 
 Reply 
 
peter
Singapore, Joined Jan 2012, 122

peter

Singapore,
Joined Jan 2012
122
05:31 Nov-05-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Peter at 05:29 Nov-05-2014 .

Hi Michel,


Second hole located at 19mm.


Peter

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
08:32 Nov-05-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to peter at 05:31 Nov-05-2014 .

Peter,
You can detect that defect at the end of full skip if time base rang was wide enough .But you cant evaluate it to 3mm SDH reference level.
I think your problem is how to select the last SDH for DAC to evaluate amplitude of toy crack.
Thickness of reference block is optional according to ASME Sec V article 4 you can select reference block same as weld metal thickness (t) or 38 mm.
But ,if your are using 38 mm reference block,it should be long enough to make DAC at full skip.
it is better to make two DAC , one for half skip with 1/4, 1/2t, 3/4t, 5/4t(1/4 at leg II), 6/4t(1/2t at leg II) SDH ,and another DAC for full skip start with 6/4 t up to 11/4 t(3/4 t at leg II).
your first SDH for DAC could be 1/4t or 1/2t for half skip distance as I'm mentioned above.



 
 Reply 
 
John
John
12:27 Nov-05-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Ali at 08:32 Nov-05-2014 .

1) this I'd getting silly, if this is for a code inspection, follow the code as written. You don't "select" which holes to use.
2) suggestion, if you would like to get responses from Americans using an American code, don't put the question entirely in metric
3) Ali. Really? Build two dacs?

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
16:47 Nov-05-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to John at 12:27 Nov-05-2014 .

John,
It is recommendation of BS EN 583-2(unfortunately I dont have BS EN ISO 16811- ed 2014) to split the DAC if any echo from SDH is out of 80%-20% FSH ,and make another DAC with different gain setting to improve signal visualization of defect at the end of V path.

 
 Reply 
 
John
John
17:25 Nov-05-2014
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Ali at 16:47 Nov-05-2014 .

Ali
The original question was regarding ASME CODE. Let's keep it simple

 
 Reply 
 
David Baeley
Engineering,
Australia, Joined Dec 2014, 17

David Baeley

Engineering,
Australia,
Joined Dec 2014
17
11:42 Jan-13-2015
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Peter at 09:00 Nov-03-2014 (Opening).

In my suggestion you can attach pipe with drilling rigs and equipments.

 
 Reply 
 
sujith rajagopal
India, Joined Jun 2015, 9

sujith rajagopal

India,
Joined Jun 2015
9
11:38 Mar-06-2017
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Michel Couture at 13:39 Nov-03-2014 .

Dear peter,

What about the length of SDH or in other words ,how much depth it should be driiled into the material. i think in ASME sec V it is stated that minimum 1.5 inches. Is there any serious problem , if it is less than 1 inch.

 
 Reply 
 
Mario Talarico
NDT Inspector,
Italy, Joined May 2010, 423

Mario Talarico

NDT Inspector,
Italy,
Joined May 2010
423
12:02 Mar-07-2017
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to sujith rajagopal at 11:38 Mar-06-2017 .

Sujith,
bad situation! If the design of the reference block does not comply with code an inspector has good cause to reject your control.

For your question, to parity of every other condition, it is clear that if the length of the hole is less than the width of the beam at the depth of the hole, the sensitivity of the control will certainly be reduced.
greetings
mario

 
 Reply 
 
sujith rajagopal
India, Joined Jun 2015, 9

sujith rajagopal

India,
Joined Jun 2015
9
05:52 Mar-08-2017
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to Mario Talarico at 12:02 Mar-07-2017 .

Dear Mario,
Thanks for reply.
So i think 38 mm will be the perfect length.

 
 Reply 
 
Mario Talarico
NDT Inspector,
Italy, Joined May 2010, 423

Mario Talarico

NDT Inspector,
Italy,
Joined May 2010
423
18:39 Mar-08-2017
Re: SELECTION OF REFERENCE HOLE-ASME
In Reply to sujith rajagopal at 05:52 Mar-08-2017 .

One less problem!
greetings
mario

 
 Reply 
 

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