Re: Re: Nozzle Flexibility factors and stiffness

From: <Christopher>
Date: Thu Jul 17 2003 - 10:04:00 EDT

>My
>question is on those nozzle joints that are commonly installed in
>the header or tanks or vessels meeting the Code requirement using
>the "area replacement" method and not subjected to cyclic loading as
>defined in the Code.

There is no general rule. Significant external loads on nozzles are to be included according to UG-22. It's up to the designer. The area replacement rule is intended to cover pressure only. I think what you will find is that vessel walls are a good deal stiffer than the attached piping and very often the external loading is negligible, but never, ever simply assume that the Code 'takes care of it.'

>By
>the way if failure do happen (nozzle under high stress load)wouldnt
>the probabale scenario be leak before break?
Not necessarily. It depends on the material, the stress level and the nozzle detail. Just for my own curiosity, what leads you to think that leak-before-break is applicable? There's nothing about leak-before-break calculations or methodology in the code. There's plenty of material requirements to insure reasonably tough steel, but nothing baout critical crack dimensions. I'm not sharp-shooting, I'm just curious how many people think there's some sort of underlying design criteria to limit crack growth.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=qILZAQoFJAqrtq-wGbhy4Nx0qo2cJ1Mc_XPIWDm_r6PtOGxjyMUkNUT6MXWD2M_ha1PEjtoBF3fQig">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 Jul 17 10:04:00 2003