Hi TP
While I do as little stress analysis as is humanly possible, I would have
thought that the sudden change in section normally encountered at a vessel
would suggest a more cautious design approach than in the "floppy"
connecting pipe. As an analogy, think of the pipe as the irresistable force
and the vessel is the immovable object.
Agree with your second paragraph, although I do note that secondary stresses
in thin walled members tend to be lower.
Hope this helps, although I doubt it.
Cheers
Steve McKenzie
-----Original Message-----
From: Tony Paulin [mailto:tony@paulin.com]
Sent: Monday, March 31, 2003 2:35 AM
To: <a href="/group/PipingDesign/post?postID=2BPzSrl_FJzM3KSXevXnITOgvF_1fbxfJL6T8imLQuBfipv7tWreuavDwDGTtxluQin0P1QSujDC8QRuu737nt1Irg">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] Re: Wrc 107
Re: WRC 107 Nozzle Load Check
We wonder what is the difference between a nozzle load in a vessel and a nozzle load in a pipe. If we don't have to take one seriously, then I don't think that we should have to take the other seriously either. The situation is, I believe, that fatigue at low cycles is not a problem for either. Most designers have not experienced load problems because they have not designed systems that cycle heavily, i.e. more than about five times a week continuously over the component's life. Once this number of cycles is reached, the safety factor on through-wall cracking (if the actual load is the design load condition), will be approximately two, with a variance of about 20% depending on how the welder felt on the day that he made the pressure containment weld on the nozzle.
Additionally, calculations are made so that the intended safety factor of the applicable Code is maintained. Just because a component does not fail, does not mean that a required safety factor is achieved. With more aggressive Codes, and thinner materials in a more competitive world extra care in a cyclic system may be warranted.
> I have wrestled with WRC and even coded a lil routine using the
> HP41. For a non cyclic type of loading where the nozzle details meets
> the the B31 reqt say for the branch reinforcement (ditto to pressure
> vessel) is it really necessary? I mean are there any documented
> failure attributed to damage to the nozzle not meeting the WRC req't -
> never heard one.
>
> Most of the desing procedure that i come across to regarding piping,
> storage tank and pressur vessel rarely even consider it. I would like
> to see a raise of hands for those designer who does go to WRC menu in
> CII during a nozzle load check.
>
>
>
> --- In PipingDesign@yahoogroups.com, "Mark Upston" <mmwind@c...>
> wrote:
> > An Excellent guideline to the use of the WRC codes
> > Published by the Pressure Vessel Research Council of the Welding
> Research
> > Council.
> > Tel : (212) 591-7956
> > <a href="http://www.forengineers.org/wrc/">http://www.forengineers.org/wrc/</a>
> >
> >
>
>
>
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Your use of Yahoo! Groups is subject to <a href="http://docs.yahoo.com/info/terms/">http://docs.yahoo.com/info/terms/</a> Received on Mon Mar 31 03:27:00 2003
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