## Allowable Stress % of yield

## Allowable Stress % of yield

(OP)

Can anybody give a detailed answer as to why the allowable stress of carbon steel (A 106) is 50% of its yield strength and the allowable stress of stainless steel is 70% of its yield strength?

B 31.3 also specifies for flanges that when we are dealing with stainless steel the allowable can be set high. By the look of it i assume it has to do with SS having greater ductility but would appreciate somebody elaborating on this.

B 31.3 also specifies for flanges that when we are dealing with stainless steel the allowable can be set high. By the look of it i assume it has to do with SS having greater ductility but would appreciate somebody elaborating on this.

## RE: Allowable Stress % of yield

ASME BPVC Section II Part D MANDATORY APPENDIX 1 BASIS FOR ESTABLISHING STRESS VALUES IN TABLES 1A AND 1B.

as referred to in B31.3:2008 302.3.2 Bases for Design Stresses footnote 2.

## RE: Allowable Stress % of yield

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"The problem isn't working out the equation,

its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

## RE: Allowable Stress % of yield

the allowable stress is based on the yield right? our use of allowable stress is to ensure that the material doesnt yield.I understand the fact that utlimate tensile is greater for SS but if allowable for SS is kept high, the room between allowable and yield is less for SS which makes it more likely to locally yield at a point?

## RE: Allowable Stress % of yield

At least that's my idea. I don't have a copy of the BPV reference above, so it would be interesting to compare my understanding of things with what that says.

**********************

"The problem isn't working out the equation,

its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

## RE: Allowable Stress % of yield

Sometimes, the 2/3 yield governs, and sometimes the 1/3 ultimate governs.