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RT technique ellipse vs superimpose

RT technique ellipse vs superimpose

Postby mohd » Mon Dec 09, 2013 4:25 pm

Dear team,

By mistake the RT crew of NDE contractor has taken 20 joints with superimpose technique instead of ellipse that was client's requirement. The client has asked re-shoot of all joints but NDE contractor has not accepted it.

Is there any way to resolve that problem?

regards,
mohd
mohd
 
Posts: 74
Joined: Mon Jul 08, 2013 2:17 pm

Re: RT technique ellipse vs superimpose

Postby Ballbearing » Mon Dec 09, 2013 10:22 pm

mohd,
What code, what diameter pipe, how many films per joint ? - more info needed.
If it was a client requirement (clearly stated in the contract or specifications) then they must be reshot at the NDT contractors expense.
Cheers,
BB
Ballbearing
 
Posts: 76
Joined: Wed Jun 12, 2013 10:11 pm

Re: RT technique ellipse vs superimpose

Postby mohd » Tue Dec 10, 2013 9:14 am

Dear BB,

Codes: ASME B31.3/ASME IX/ASME V.

case 1: 2" pipe SA-106 Gr B with thickness 5.54 mm (13 joints)
case 2: 2" pipe 316L with thickness 3.91 mm (7 joints)

number of film using ellipse technique: 2
number of film using super impose technique: 3

regards,
mohd
mohd
 
Posts: 74
Joined: Mon Jul 08, 2013 2:17 pm

Re: RT technique ellipse vs superimpose

Postby Ballbearing » Tue Dec 10, 2013 11:17 am

Mohd,
When you say "clients requirement" - what did you mean ?
Does the project specification state they must be ellipse or they must be in accordance with ASME V ?
Cheers,
BB
Ballbearing
 
Posts: 76
Joined: Wed Jun 12, 2013 10:11 pm

Re: RT technique ellipse vs superimpose

Postby mohd » Tue Dec 10, 2013 2:49 pm

Dear BB

Thanks,

I just want to know what is the advantage of the ellipse technique with respect to the super impose technique. Most of project specifications of our projects require ellipse technique for diameter 2" or less.

regards,
mohd
mohd
 
Posts: 74
Joined: Mon Jul 08, 2013 2:17 pm

Re: RT technique ellipse vs superimpose

Postby Ballbearing » Tue Dec 10, 2013 10:03 pm

Mohd,
Both elliptical and super-imposed techniques are acceptable as per ASME V.
Elliptical is definitely the preferred method - generally the only time super-imposed is done is if there are problems with access (cannot get the required stand-off for the ellipse) or the RT technicians are too lazy to set up an ellipse.
Economics wise you are paying for one extra film (in your case 20 extra films) and adding additional time for 3 shots with super-imposed rather than 2 shots for elliptical.
Identifying the exact location of defects with super-imposed can be a little more difficult than elliptical due to the fact you are "blowing" the near side weld straight on top of the far side weld (that is why 3 shots are required).
Hope that helps,
Cheers,
BB
Ballbearing
 
Posts: 76
Joined: Wed Jun 12, 2013 10:11 pm

Re: RT technique ellipse vs superimpose

Postby mohd » Wed Dec 11, 2013 8:29 am

thanks BB.
mohd
 
Posts: 74
Joined: Mon Jul 08, 2013 2:17 pm


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