UG-16(c) not good enough for AI?
UG-16(c) not good enough for AI?
(OP)
An AI is threatening to reject vessels made of SA-516 (i.e. subject to SA-20 tolerances) plate which are delivered within tolerance but thinner than the required thickness. I think I'm covered by UG-16(c), but I'm new to Sec VIII. Will someone double check my logic before I make a fool of myself?
E.g. Vessel requires 0.495 after considering pressure and corrosion. I specify SA-516 Gr 70 at 0.500in. Mill delivers 0.01in under, or 0.490in. This is less than the required thickness, but within the tolerance of 0.01in.
The way I read it, UG-16(c) applies and I can use the plate to the full design pressure for the thickness ordered.
SA-20 limits the under tolerance to 0.01in. 0.01in is less than 6% of 0.5in. So the tolerance is not more than that required for UG-16(c) to apply. Ergo, so long as the delivered plate is within spec, I can use it!
[Conversely, if my PO inexplicably loosened the under-tolerance to 0.011in, I would be SOL and the AI would be justified in rejecting the material.]
E.g. Vessel requires 0.495 after considering pressure and corrosion. I specify SA-516 Gr 70 at 0.500in. Mill delivers 0.01in under, or 0.490in. This is less than the required thickness, but within the tolerance of 0.01in.
The way I read it, UG-16(c) applies and I can use the plate to the full design pressure for the thickness ordered.
SA-20 limits the under tolerance to 0.01in. 0.01in is less than 6% of 0.5in. So the tolerance is not more than that required for UG-16(c) to apply. Ergo, so long as the delivered plate is within spec, I can use it!
[Conversely, if my PO inexplicably loosened the under-tolerance to 0.011in, I would be SOL and the AI would be justified in rejecting the material.]





RE: UG-16(c) not good enough for AI?
Of course there's always App 32.
RE: UG-16(c) not good enough for AI?
As weldtek has mentioned, your spec may be a little close for comfort, but hey maybe your fabrication practices are top notch and you can spec on the limit to win jobs. Well done.
RE: UG-16(c) not good enough for AI?
RE: UG-16(c) not good enough for AI?
RE: UG-16(c) not good enough for AI?
How is cutting it this close on nominal wall vessels any different than cutting it even closer on mill run minimum wall vessels?
In my short time in vessels, I've seen several such vessels. In my piping experience, min wall pipe was common, even in piping requiring an ASME stamp from an AI.
All this is from the point of view of a specifying engineer. I've not been with the actual fabricator seeking the stamp.
RE: UG-16(c) not good enough for AI?
RE: UG-16(c) not good enough for AI?
I guess not much, but over the years I've seen several situations where designing too close resulted in issues for the shop. In one case on a very heavy wall vessel, just rolling it on turning rolls deformed a local section on the shell thinning it just enough to cause a problem. Why go there?
BTW, should you need the info for your A.I., there's at least two interpretations on this subject. VIII-1-86-67 and VIII-1-04-92.
RE: UG-16(c) not good enough for AI?
Regards,
Mike