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UT - vertical space requirements?

UT - vertical space requirements?

UT - vertical space requirements?

I got a contractor's RFI today, regarding a steel frame being fabricated in a shop. The fabricator's approved shop drawings showed 100% UT on most of the groove welds. Now, that they've gotten to one weld detail, they're saying that there isn't enough vertical space to correctly UT. And they would like to 100% MT this detail, instead. (picture below)

I'm not all that familiar with NDT and was hoping to get some feedback...

1. I'm having trouble visualizing how there isn't enough vertical space. For the "T-connection", is there just not enough height for the beam to refract fully and properly for good readings?

2. These are just horizontal keeper bar welds, which I don't see as being all that critical, but there are high vertical loads (100's of kips). How significant is the loss of "accuracy" when switching from UT to MT in a shop environment?


RE: UT - vertical space requirements?

The sketch is completely un-readable on my 15 in laptop. Saving the sketch to my desktop and opening in a viewer wasn't any help. I wonder how big a monitor one would need.



The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: UT - vertical space requirements?


RE: UT - vertical space requirements?

Not butter, but readable. You may now get some useful info from a UT expert here. I'm not one of 'em.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: UT - vertical space requirements?


As a minimum you will need the base metal to extend beyond the weld by the weld thickness plus 1/2". That will get you a half node test. Ideally you should have 2 to 3 times the weld thickness of base metal beyond the weld seam.


RE: UT - vertical space requirements?

Many times I have come across this situation.
If it is approved by you the report will have a note stating "Partial Test Only due to limited access" or words to that effect with a sketch showing what area has not been UT tested.
Two things to consider.
Has the fabricator made a mistake in assembly and "blocked" a weld when it could have been 100% UT tested before assembly ?
NDT is all about confidence - if the weld in question has been performed by a welder with no repairs and all other welds tested previously were repair free then you can have confidence the weld you cannot test will be OK.
On the other hand, if there were welding issues with other welds tested you would have less confidence.
Hope that helps,

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