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Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

(OP)
I am looking at SA-193 and A-193 Grade B8 Class 2 (304 stainless steel) allowable stress values in B31.3 and B&PV Section II.

The diameter I am looking at is < 3/4".

Does anyone know why the allowable stress values are different in B31.3 vs. B&PV Section II?  The codes appear to use the same rules for determining allowable stresses from reading the passages in the corresponding codes for how the stresses are calculated.

RE: Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

Because they are different Standards, service applications, conservatism and different committee volunteers.

RE: Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

I've heard repeatedly that gaskets leak if you limit your bolts to Section II allowables. Therefore explaining a fanatical insistence, in my neighbourhood anyway, that the bolts are always part of the piping system, not part of the vessel.

This is hearsay. I've never experimented nor researched this myself.

RE: Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

You can have flanged pressure vessel halves and the bolts would be Section VIII.

RE: Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

And you can attach piping to that vessel and the bolts are per B31.X.

What is curious is if the vessel Metengr mentions operates below -20F, Section VIII allows you to use A193 B7 to hold the vessel together while B31.1 makes you use A320 L(7, 47, and several other choices) to attach piping to it.  Go figure.

I wish the committes would call a joint session and get on the same page.

rmw

RE: Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

rmw;
It would be like herding cats.
 

RE: Why are bolting allowable stresses different in B31.3 vs. B&PV Sec II

grin...

rmw

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