Re: pressure test thoughts

From: <Christopher>
Date: Sun Sep 11 2005 - 18:05:00 EDT

On Sep 11, 2005, at 8:41 AM, John Luf wrote:

> In general they cannot be re-rated (FEA has been used
> by some for this but frankly I am a strong dissenter
> in such practices...

There's and interesting distinction I hadn't thought about. The ANSI flange ratings are pretty conservative because the gasket loading assumed in design is high and the rating, ie. CL 600 applies to a pretty high temperature. I wouldn't have any qualms about using a CL600 flange at a higher pressure than 600 psi if the ASME Code App 2 calculations worked out. I don't think that's re-rating, though.

BTW, I heard from someone in an authorized inspection agency who knows for sure about such things, and the 're-rating' process he describes is what I've always thought it was--repairs or alterations done in accordance with the NB Code. That Code requires that the vessel carry an NB 'R' plate alongside the original Code plate, with the new pressure and temperature rating. Anyway that's how his agency does it.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=U7VDVlMd6DvKQGMuwKEnKlpSQMseKz705VgZPfTUPct_YjYTNsFbuwsNRe-CTN20LV_PmlAmHs7pMbUtiQ">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 Sun Sep 11 18:05:00 2005