RE: Transient stresses

Mr. Wright,
I am the person who addressed the question to the forum people. My concern is with transient thermal stresses. Specifically I must evaluate the transient thermal stresses that arise in a pump discharge piping system when the pumping product is changed from propane at -41oC to butane at -5 oC. This is an 18" OD header of 1 mile long. As butane displaces propane I realize that there will be local stresses in the "butane front" and there will also be expansion stresses as the system is changing its temperature. I know that the Code can not treat every single aspect of every system as this is the designer job. The Code gives the concepts of what must be considered. The purpose of my question is to know if anyone of the forum has done this type of analysis how he, or she, did it in general sense. I do not pretend to be explained in detail as this is not the object of this forum. Thank you very much for your cooperation.

Anibal Arias
  SEMTEC
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De: <a href="/group/PipingDesign/post?postID=TozoWSexPxZGq523iKxaBq3V_9DvYhTAX-I2VXr4RcnX3fddodFvaygqb6pv-8PcYPBoHr3QqWxK5bAgyu46E3rljiSGYbI">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=TozoWSexPxZGq523iKxaBq3V_9DvYhTAX-I2VXr4RcnX3fddodFvaygqb6pv-8PcYPBoHr3QqWxK5bAgyu46E3rljiSGYbI">PipingDesign@yahoogroups.com</a>]En
nombre de Christopher Wright

Enviado el: Domingo, 11 de Noviembre de 2007 05:11 p.m.
Para: <a href="/group/PipingDesign/post?postID=TozoWSexPxZGq523iKxaBq3V_9DvYhTAX-I2VXr4RcnX3fddodFvaygqb6pv-8PcYPBoHr3QqWxK5bAgyu46E3rljiSGYbI">PipingDesign@yahoogroups.com</a>
Asunto: Re: [PipingDesign] Transient stresses

On Nov 11, 2007, at 7:58 AM, sviswan@technip.com wrote:

> Does the design code describe how transient stresses are to be
> treated.
The codes only prescribe criteria for particular stress categories.
These are pretty clear. Analysis methods or construction of system
loadings are the left up to the designer or the owner.

Remember there are lots of different tyes of transient loading--start-
up, shut down and seismic loadings come to mind first. Most of these
are unique to a particular site or system, so there's no practical
way for all possible transients to be specified quantitatively in a
Code, beyond basic system response criteria.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a>

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