Stepping in here a bit late but:
I have seen a number of vessels/piping systems uprated in the natural gas
industry. Situation being that the original design had adequate strength/wall
thickness for some value. But the customer was only interested in a lower
number, so it was tested and stamped or certified for the lower rating. At a
later date, they wanted a higher rating. So, checked calculations, re-tested,
and re-certified at the actual capability.
George McKinney
On Sep 7, 2005, at 9:18 PM, jcluf wrote:
> I assure that I have been involved with and charged many profitable
> hours in re-rating piping systems.
I'll defer to your experience. In fact I've been asked to 're-rate'
vessels on occasion. I wouldn't touch it because I have absolutely no
idea of the vessel's actual service, and because it violates the
National Board rules, as I've mentioned. I think it violates most state
pressure vessel laws, too, although Minnesota makes allowances for the
use of non-Code vessels, so presumably other states do too. Your point
about spotty regulation is well taken, but it seems like you're talking
about loopholes in laws, not engineering practice.
I'm probably giving some offense here, but I've seen a few cases of
something very much like 're-rating,' one in particular where a
second-hand tank was put into service with the original code plate
chipped off and a scrapped code plate slipped into the little frame
where the flammability tag is placed. The vessel later blew up when the
botched welds over a patched inspection opening let go. Probably not
what you have in mind when you talk about re-rating, but this vessel
had supposedly been 'checked out,' too, and probably the guy who did it
charged some profitable hours, too. But the plant burned down, anyway.
That said, I suspect it's theoretically possible to re-rate a vessel,
provided you know enough. I've just never seen a vessel where anyone
actually knows enough. But I'll check out the piping Code appendix
anyway.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
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[Non-text portions of this message have been removed] Received on Thu Sep 08 13:06:00 2005
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