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Technical Discussions
ut tech
ut tech
08:53 Feb-23-2010
basemetal indications

Level 2 ut tech finding several non-lamilar indications in the basemetal outside of the heat effected zone. Scanning to aws D1.1 with manual sherwave and can not find accept/reject criteria for this. The code talks about lamilar indications but there is no info on n on lamilar. They can't be rejected with a straight beam transducer.

    
 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 819

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
819
13:19 Feb-23-2010
Re: basemetal indications
In Reply to ut tech at 08:53 Feb-23-2010 (Opening).

It would appear the metal is of pour quality. What I suggest is to find the ASTM stardard pertaining to the metal and quality you or your customer is suppose to have and see what the acceptance criterias are.

    
 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
09:41 Feb-24-2010
Re: basemetal indications
In Reply to ut tech at 08:53 Feb-23-2010 (Opening).

The problem is that when you are conducting a weld examination, the object of the examination is to check for weld defects. In order to do this satisfactorily you have to scan through the base metal with angle probes (search units). The reason for the base metal examination, prior to the weld examination, is to ensure that the base material is homogeneous and therefore allows the ultrasound to pass through.

So, the base metal examination is only to determine whether there are inhomogenities present that will interfere with the weld examination. This means in practice, if the indications are large enough to interfere with the weld examination, you report this to your client. Now, he won't be very happy because 1. his weld hasn't been examined. 2. His plate material might be useless.

The next step would be to carry out a lamination examination of the plate material and this examination uses a different code which does include accept/reject criteria.

Horses for courses!

    
 
 
ut tech
ut tech
10:32 Feb-24-2010
Re: basemetal indications
In Reply to Jon Wallis at 09:41 Feb-24-2010 .

The problem is that the indications do not show up with the lam scan. They are only detected with an angle beam shear wave transducer. The material is relativaly thin when looking at AWS D1.1 so the alternative scans dont really help either. The problem that we need to solve is wether we reject them and scrap or repair the areas or if we provide as much info about them as possible and leave them alone. They are also not rejectable to ASTM 578 (I believe that is what we needed to look at but dont have the info in front of me rt now).

    
 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
12:44 Feb-24-2010
Re: basemetal indications
In Reply to ut tech at 10:32 Feb-24-2010 .

Ok, I should have read your original question better, sorry.

It looks like you have randomly orientated inclusions in the base metal material. If the code requires you to examine only with a straight beam (sorry I don't have the AWS code at hand - not much call for it in my sphere of ops.) then stick to the code for reporting purposes and report verbally to the client the problem.

Maybe you need to get a sample of the plate analysed or speak with the construction engineers as to fitness. Are the indications surface breaking? If so, it may be cracking!!!

    
 
 
ut tech
ut tech
02:53 Feb-25-2010
Re: basemetal indications
In Reply to Jon Wallis at 12:44 Feb-24-2010 .

They aren't surface breaking and not crack. Maybe silica builups but have a rejectable rating but are/out of the weld an d haz.

    
 
 

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