X-ray Slot Weld on Assembled Pressure Vessle?

[mae1778]

I have a pressure vessel made from 6061-T6 about the size of a small air compressor that’s undergone proof testing. I’d like to do nondestructive testing on it to verify no cracking occurred during the test. Particularly curious about some slot/plug welds that we have on internal bulkhead flanges to the skin.

Borescope results show that bulkhead flanges are not in intimate contact with the skin away from the weld. The skin is pulled into contact at the weld. My experts are telling me that this will make UTI unreliable and pretty much meaningless.

1). Is that true? Can I not get meaningful results with an experienced UTI Driver?
2). If true, can it be x-rayed? My same experts are telling me that the xray results will be inconclusive because there is no way to put a plate inside the assembly.

Is there seriously no way to do anything more than visual inspection and DPI? Any suggestions on how I should proceed?

 

[TED7]

If the cracking you're looking for is surface breaking, why would you not penetrant test?

If you can't put a plate inside the assembly, can you not put the plate outside and the source inside (it'll be gamma rays not x-rays but still RT)?

 

[Ron]

If you can't put a plate inside the assembly, can you not put the plate outside and the source inside (it'll be gamma rays not x-rays but still RT)?

Exactly. A gamma ray source tube (Ir 192) can be inserted into a hole that is about 1/2" or so in diameter. Film is then placed on the outside.


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[mae1778]

I could be wrong, but if we had a crack that didn’t actually make it to the surface, a penetrant inspection wouldn’t show anything would it? I have evidence on another part that suggests the crack would start on the IML and progrates outward, but does not go all the way.

Assume we don’t have easy access to the interior. In my simple mind, why can’t you just take an image at a 45,90,-45 angle with the source and plate on the outside or something along those lines?

 

[Ron]

You can. Do it....as long as the source is on the inside and the film is on the outside.


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[TED7]

You can attempt to shoot the whole component if it's small enough. Pipe welds are often shot at an angle (45° for example) with the source one side and the plate the opposite side. It gives an oval image of the entire weld but you might get depth of field issues with some of the image out of focus, plus you'll obviously have both sides of the vessel overlapping on the plate, you'll have to have some way of determining which surface the defect lies on.

If you've got a pressure vessel, surely you've got a nozzle or some other penetration that you can insert a source through?

If you've got legitimate reason to believe there may be a volumetric defect, DPI won't help you, it's just convenient sometimes to discover a surface breaking defect with 'spray paint' before you go through the whole process of radiography.

 

[DekDee]

You can do any of the above but it is time and money.
If you have no problem with those then go for it.
If you have a specific bulkhead you are worried about shoot from outside, film outside (2 shots).
One slightly off centre to one side, one slightly off centre to the other side.
Very hard to describe what I am trying to say - hope you understand.
Rather than us trying to describe to you - why not ask a reputable NDT company to come and explain what they can and cannot do ?

 

[Ron]

DekDee...yes, both source and film can be on the outside; however the shot times will be increased a lot, which will increase the cost of testing.


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