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Technical Discussions
Muhammad Azhar
Muhammad Azhar
06:43 Aug-02-2011
aws d1.1

kindly, plz help me to use the table 6.3 of aws D1.1.
1)I have set my reference db at 80% b=54.2 db
indication level a= ?
give any numerical example to calculate indication level.

2) attenuation factor c=(soundpath-1)*2
kindly give numerical example to calculate c. & sound path.

3)after calculating these values.I m facing difficulty in understanding table 6.3.

a)scanning level table is given at the bottom.what is the purpose of it?? & how to use it.give numerical example plzz

b)how to read and use table 6.3.plz help me by considering any umerical values.so that i can understand it properly.plz help me. I am in a very bad situation.I m level II and i have to perform ut of cyclic structure & i m unble to understand it.help me .

    
 
 Reply 
 
Ed T.
Ed T.
07:03 Aug-02-2011
Re: aws d1.1
In Reply to Muhammad Azhar at 06:43 Aug-02-2011 (Opening).

Yoy need to tell us your indication dB level before you set it at 80%. What was it originally?

    
 
 Reply 
 
Gowrisanthosh Palika
NDT Inspector,
Royscan engineering pte ltd, Singapore, Joined May 2008, 52

Gowrisanthosh Palika

NDT Inspector,
Royscan engineering pte ltd,
Singapore,
Joined May 2008
52
08:34 Aug-02-2011
Re: aws d1.1
In Reply to Muhammad Azhar at 06:43 Aug-02-2011 (Opening).

Hi
AWS D1.1 UT evaluation is some difficulty comparing other codes/standards but if u understand it once it is so easy.
a-b-c=d is the key of our evaluation
Where
"a" is indication level dB (indication set at reference level 80%, note dB from your screen. For numerical example 50)
"b" as you know reference dB (from1.5mm SDH V1 , for example 45)
"c" is attenuation rating, can calculate from the formula c=(BP-25.4)x0.079 (beampath taken from indication level dB beam path, example c=(50-25.4)x0.079 > c= 1.94. )
"d" is mentioned clearly in table6.3
Now use values in formula
a-b-c=d
50-45-1.94=3.06
Then go through table6.3 and evaluate
And lastly scanning levels given in tables, add to reference dB and scan according to beampath( for example if u want to scan 10 mm thick, for 70degree half beampath is nearly 30. Then follow scanning level table)
May helpful to you.
Regards
Gowrisanthosh

    
 
 Reply 
 
azhar
azhar
14:23 Aug-02-2011
Re: aws d1.1
In Reply to Gowrisanthosh Palika at 08:34 Aug-02-2011 .

thnaks for helping me out .....it was realy helpfull but kindly elaborate how to use table 6.3 plz give any numerical example .plzzz

    
 
 Reply 
 
mahesh
India, Joined May 2011, 5

mahesh

India,
Joined May 2011
5
14:22 Aug-18-2011
Re: aws d1.1
In Reply to Gowrisanthosh Palika at 08:34 Aug-02-2011 .

Dear all

But I have some doubts

1) In formula C =(BP-25.4)x0.079 why we have to deduct 25.4 and multiply by 0.079 ?
I mean to say that what is 25.4 and 0.079.

2) In AWS D1.1 its showing like below

The “Attenuation Factor C on the test report shall be attained by subtracting1 in.
[25 mm] from the sound-path distance and multiplying the remainder by 2. This factor shall be roundedout to the nearest dB value. Fractional values less than1/2 dB shall be reduced to the lower dB level and thoseof 1/2 dB or greater increased to the higher level.

Please explain

thanks

    
 
 Reply 
 
Musali
Musali
06:39 Aug-19-2011
Re: aws d1.1
In Reply to azhar at 14:23 Aug-02-2011 .

Dear Mr. Azhar,

I will try to explain with an example for the Table 6.2 which is very similar to 6.3.

For example if you have a thickness 25 mm which is falling in the range of 20 to 38 mm thick in the table and you will choose automatically 70 deg angle probe for scanning.

after scanning and calculating the d value (d=a-b-c ) and length of defect will become the deciding factor for accept/reject criteria.

1. If the d value is 2 or lower then the discontinuity severity comes under the Class A and it is eligible for rejectance irrespective of length.

2. If the d value is +3 then it comes under the Class B. In this case if the length of the discontinuity is more than 20 mm then it is rejected.

3. If the d value is +4 then it comes under the Class B. In this case if the length of the discontinuity is more than 50 mm then it is rejected.

Note:
- If the length of the defect is 10 mm and it is located at less than 20 mm from
the end then Class B & Class C welds are eligible for rejectance.

- If the length of two discontinuities is 10 mm and 15 mm respectively, and it is
separated by more than 30 mm, then it is acceptable

4. If the d value is +5 and higher then the weld is under Class D, and irrespective of length of discontinuity it is acceptable.

Scanning Levels:

For example, if you are scanning 10 mm thick with 70 deg probe, then the half sound path distance will be 30 mm approximately. This 30 mm comes in the range < or = 65 mm and you need to add 14 db for the reference db.

Reference db can be found using the 1.5 mm hole dia in the calibration block and for example if it is 45 db, then the scanning db will be 45+ 14 = 59 db.

Hope this clarifies

    
 
 Reply 
 
gnanaguru manickam
gnanaguru manickam
10:08 Feb-15-2012
Re: aws d1.1
In Reply to Gowrisanthosh Palika at 08:34 Aug-02-2011 .

thanks for your explanation of aws d1.1, its very helpful to me

    
 
 Reply 
 
john
john
16:18 Feb-15-2012
Re: aws d1.1
In Reply to Muhammad Azhar at 06:43 Aug-02-2011 (Opening).

The first thing that was done incorrectly is your reference level. As i see on this post quite often, 80%FSH is incorrect, "...results on the display between 40% and 60% FSH...". 50% in what is normally used. If you start off with 80% FSH, the scanning level to use for a particular sound-path is made even higher resulting in even more "noise" on the screen.

The second critical thing that I see wrong is that the "Qualification Requirements" don't appear that they are being followed. If followed correctly, you would not have these questions and the reference level would be correct. "....the qualification of the UT operator shall include a specific and practical examination which shall be based on the requirements of this code. This examination shall require the UT operator to demonstrate the ability to apply the rules of this code in the accurate detection and disposition of discontinuities."

I do hope your questions are in regards to training, and not an actual inspection that you are performing.
I don't mean to be harsh, but proper adherence to the codes being used is critical to the tables and acceptance/rejection criteria working properly to insure the safety of the public.

Regards

    
 
 Reply 
 

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