Re: Preliminary Nozzle Loads

From: <Christopher>
Date: Fri Dec 02 2005 - 11:32:00 EST

On Dec 2, 2005, at 8:16 AM, Ken Nisly-Nagele wrote:

> What approach do members use for determining preliminary allowable
> loads
> (forces and moments) on carbon steel pressure vessels?
This is very much an ad hoc thing, because of differences in vessel service. For that reason the assessment of other loading is is given pretty much a lick and a promise in UG-22 and comparable parts of the other Code sections because standard loadings don't exist. It's made the responsibility of the owner or his representative, which is another way of say the designer or the guy who writes the specs. When a question comes up I use FEA, which is pretty easy with pressure vessels--much easier than manual methods like WRC-107 or the follow-on reports. FEA is really the only productive way to address dynamic loading or thermal loading.

There are references in the Codes to certain specifics, like the Zick analysis for saddle supports or WRC-107 and other bulletins based on the same methodology. If wind of seismic loading is a question, there's an example problem about how it's addressed in Appendix L but only large standing equipment placed outdoors will be subject to such loading. In small vessels experiencing high pressure the dead weight and attachment loading is usually minor compared to the internal pressure. Hydrostatic test loading may or may not be important, although I worked on a project once where the whole thing was driven (the owner eventually saw reason) by loading due to hydrostatic testing. It was a large wind tunnel circuit, several hundred feet in length with an average diameter of about 13 feet. You can imagine the weight of water needed to fill it for a one time test.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=Lj4e1l6JdTIDGLGyLCcVYoJk0Vnemzeq787yfrCpICFRQxO9yWFDp9xe33DPEvbr8oIsiq2G3PlpbA">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 Fri Dec 02 11:32:00 2005