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374 views
00:27 Sep-25-2002

Miguel Suarez Arana

Engineering
Servipetrol,
Bolivia,
Joined Sep 2002
1
ASME B&PV Secc V Art. 2 and 22

There is a possible misunderstanding in the interpretation for the appropriate IQI selection when using double wall-double image technique which states in the Art. 2 that the IQI selection has to be done based in the single wall and a sketch showing this is contained in the 95 Ed. and in the 98 Ed. Add. 2000, while in the former this was cleared in the Art. 22 (e 747) stating to be careful when exposing DW/DI there has to be selected the IQI bases in the double wall, the latter edition does not states this, probably for the respect to the original ASTM standard (the title also was changed here).
Our concern is that , being well versed in the RT technology, we consider that omitting a clear up confusess some inspectors not familiar with the RT in this special case.
We would appreciate very much if you agree with us in using the IQI based in the double wall thickness only for the DW/DI technique


 
00:10 Sep-27-2002

Juan Amado

Engineering, Inspection
Arco Industrial, S.A.,
Panama,
Joined Nov 2001
44
Re: ASME B&PV Secc V Art. 2 and 22 We have performed many RT inspections utilizing the DW/DI technique, and have always managed to comply with the IQI wire diameter apropiate for the single wall thickness. Furthermore, it makes sense that the IQI selection be based on the single wall thickness because since the weld being evaluated is equivalent to only one wall of the pipe, the indications to be detected must be in the range of only one wall thickness. The difficulty with the method stems from the fact that there is added distance between the side of the pipe that is far from the film thus making it more difficult to show the appropiate wire image on the radiograph. The only way to mitigate this effect is to increase the source to object distance. For tubes of 2" to 3" nominal diameter we have found a 24" to 30" source to object distance yields good results.

: There is a possible misunderstanding in the interpretation for the appropriate IQI selection when using double wall-double image technique which states in the Art. 2 that the IQI selection has to be done based in the single wall and a sketch showing this is contained in the 95 Ed. and in the 98 Ed. Add. 2000, while in the former this was cleared in the Art. 22 (e 747) stating to be careful when exposing DW/DI there has to be selected the IQI bases in the double wall, the latter edition does not states this, probably for the respect to the original ASTM standard (the title also was changed here).
: Our concern is that , being well versed in the RT technology, we consider that omitting a clear up confusess some inspectors not familiar with the RT in this special case.
: We would appreciate very much if you agree with us in using the IQI based in the double wall thickness only for the DW/DI technique
.



 


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