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Anonymous Poster

Allowable Stress: High Pressure Pipe Design

08/22/2010 10:07 AM

As per chapter IX of ASME B31.3, Allowable stress is calculated 2/3 of yield stress only;

I wonder why allowable stress for high pressure piping is calculated based on yield stress only and why no credit for ultimate tensile stress?

As per ASME section VIII div-1 and div-2, allowable stress is calculated based on yield as well as tensile stress then why it is different in ASME B31.3.

Can someone through some light on this subject.
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Anonymous Poster
#1

Re: Allowable Stress: High Pressure Pipe Design

08/23/2010 12:32 AM

The properties of material will calculate base yield, when u see the diagram the elastisitas start at yield st. that mean mechanical properties start change also that way choosing yield st.
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PWSlack
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#2

Re: Allowable Stress: High Pressure Pipe Design

08/23/2010 4:08 AM

As the UTS is greater than the yield stress, would it make any sense to extend the piping beyond its yield stress, thereby eliminating any prospect of its returning to its original shape when the pressure is reduced <rhetorical question>?

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MrGeneRall
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#3

Re: Allowable Stress: High Pressure Pipe Design

08/26/2010 3:19 PM

I believe Section VIII deals with pressure vessels in general.

It would be my guess that a change in the volume of a pressure vessel could cause a harmful situation. When you hit the yelid strength, you enter a region where you plastically deform the object and, as a consequence, you increase the volume.

My bet is they are using the yelid strength because they want to guard against a change in volume.

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