A 106 Gr B allowable stress 1

[sbnz]

The allowable stress for A 106 Gr-B pipe is 17,100 psi (-20º to 650ºF) as per ASME B 31.1- Addenda 2005 (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.

 

[insult2injury]

If the piping is non-boiler external piping, then B31.1 would be the applicable code as identified that document.

I2I

 

[tickle]

sbnz

Answer in part

ASME VIII div 1 applies contingency/conservatism by using lower stress values

ASME VIII div 2 applies contingency/conservatism by employing greater checking, testing (NDT) etc.

Hope that assists

 

[jte]

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

 

[Giuss]

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 20000Psi up to 300°F (design according ASME VIII div.2) and 17100PSI up to 650°F (Design according to ASME VIII div.1), 20000 PSI up to 400°F (ASME B.31.3).
I neaver heard of an allowable stress value for A 106 Gr.B greater than 20000 Psi...........but i don't know all Design codes...........but it sounds very strange.

 

[BigInch]

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.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[Giuss]

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 (35000 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 25200 not 30000 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

 

[BigInch]

You're right. It is SMYS that is given in the code, as allowable stress is found only after applying the class location design factor (always 0.72 for B31.4). And you're right about the 35000 yield. I just mentioned this to note that the resulting allowable stress is over 20,000 psi, for all cases except the 0.4 class location design factor given in B31.8

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain