The allowable stress for A 106 Gr-B pipe is 17,100 psi (-20º to 650ºF) as per ASME B 31.1- Addenda (which we have a copy). I gather the allowable stress for same material as per ASME VII Div 2 (which we do not have a copy and can't actually check) is 24,300 psi ?
Can somebody confirm me if that is correct and if so, why are the allowables different in the codes and which one should be used for piping design?
Must be a very silly question to people more familiar with the codes and materials. Thanks in advance for educating.
which one should be used for piping design?
Well, one would usually use the
piping code for
piping and the
vessel code for
vessels. But are you sure that B31.1 is the right application for your piping and not one of the other B31.x codes? Perhaps this is going into a refinery or maybe its for a pipeline?
If your application is for a vessel, you'll need to decide whether to go VIII Div. 1 or Div. 2. Since you're asking this question, may I strongly suggest Div. 1 rather than Div. 2?
jt
sbnz,
Obviously you have to verify the applicable/contractual Design Code as all have already told you
Anyway the values they indicated you for Allowable Stress of A 106 Gr.B according to ASME VIII and listed in ASME II part D are wrong.
The values are Psi up to 300°F (design according ASME VIII div.2) and PSI up to 650°F (Design according to ASME VIII div.1), PSI up to 400°F (ASME B.31.3).
I neaver heard of an allowable stress value for A 106 Gr.B greater than Psi...........but i don't know all Design codes...........but it sounds very strange.
B31.4 & 8 put it at 30,000
The different codes address typical conditions prevalent in each specific industry, hence allowables and methods of anlaysis and other provisions can quite logically vary accordingly.
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
Big Inch,
I'm not used with the codes you mentioned becouse my experience is mainly based on Downstream (my code is ASME B.31.3) but i didn't find evidence of that you wrote.
ASME B.31.8 doesn't refer to a ''Allowable Stress Value''but uses the minimum Yield Strength ( in our case), which is a mechanical property of the material as indicated in the relevant product specification (e.g. ASTM A 106), for wall thickness calculation but the formula includes both a temperature-derating factor and a Design limiting (0.4-0.8) factor.
It's true that ASME B.31.4 gives a very high allowable stress for ASTM A 106 Gr.B but it's not psi and the values is limited to 120°C.
I'll say again i'm not used to this Codes, if is there i didn't consider or i misunderstood, please correct me.
Giuss