Re: B31.1 SV Nozzle Design

From: <Christopher>
Date: Tue Feb 13 2007 - 23:36:00 EST

On Feb 13, 2007, at 9:42 PM, John Luf wrote:

> "I have been told that the nozzle design must
> also be adequate for 6000 psi moment of thrust from valve discharge."
> Moments are Force x Length therfore there is no such a thing as a PSI
> moment.

Absolutely right. I should have mentioned it then so I will now--what does the 6000 psi figure apply to? Is it a stress limit or an actual moment with the units wrong? It's also not clear how the moment is applied. The relief valve discharge wouldn't exert a moment if it were applied normal to the center-line of the pipe, but if the outlet were directed at 90 deg the offset load would produce a moment.

I'll stick to my guns on calculating the stress. You'll need to calculate a value for the SIF applicable to the moment and concentrated radial load. The SIF for pressure isn't correct for externally applied loads. WRC-107 is one way of doing it.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=Y0ymJrlg94FLYss3vXcAuMksHcRJdAvC-RDwI6IkOb6JjdvrpjJ88QIdc4lsI470kfS8qUqQWuIiPHZUxbk">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 Tue Feb 13 23:36:00 2007