Re: pressure test thoughts

From: <Christopher>
Date: Thu Sep 08 2005 - 15:12:00 EDT

On Sep 8, 2005, at 1:37 PM, George McKinney wrote:

> I have run into this a number of times - a mfr. might have a vessel
> designed and possibly built, but not tested. Customer wants a vessel
> NOW, and didn't need the full MAWP. So, it was tested and stamped for
> something less than its actual capability.
I don't mean to be obtuse, but I still don't see why. The manufacturer won't cut his price for an already built vessel, so there's no cost or delivery advantage. Chances are the manufacturer already has the Code plate ready; the test costs what a test costs--no advantage to testing the vessel for a lower pressure. I've run into cases where there was a slight cost advantage in not radiographing a vessel and simply reworking the calculations with a lower MAWP from the lower joint efficiency, but the only savings would be a few hundred dollars in NDE expenses and such a vessel couldn't be re-rated higher down the line, because the corresponding NDT wasn't met. We're not talking about API or UL storage tanks, are we? We mean real pressure vessels with Code plates?

I've been working with ASME Code vessels and Code Committees since 1968, and this is the first time I've ever run into such a thing. I've run into questions a lot and every time I've talked to the AI or some Committee about it I always got the same answer. The code plate means it was built in a certain way and the Code plate means only that. Once it's shipped, the only mods you can use to maintain the Code plate need to comply with the National Board Repair Code. The NB Code says the best you can do is bring it back to compliance with the original Code. I know each jurisdiction can make some exceptions, but the ASME Code is the standard. I'm sure there are a few states who haven't adopted the ASME Code as the technical basis of the pressure vessel laws, and probably more states like Minnesota which will permit non-Code vessels, provided you jump through some hoops to show that it complies with the Code, including annual testing, but I swear to God, upgrading is a new one on me. I'd really like to hear more, but get set for some involved questions.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=nY_45NJZ3w0wE7gV1hpcjQotoZKsyqf-VQUPqi4aKGECXxWYCouz2qIG-7u3YdXAQmHKC16DKoGN">chrisw@skypoint.com</a> | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a> Received on Thu Sep 08 15:12:00 2005