Difference in allowable stresses in ASME Secton II part D & B31.3 1

[Meck91]

I went through some of the relevant threads with respect to above and found useful info. from seniors on this, but i would like to know the reason for this difference in allowable stress for material listed in both Secton II Part D & B31.3, for example Material SA 516 Gr. B can be used for Pressue Vessel as well as for piping but at all times if i am designing piping i have to use values from tables available in B31.3. Why i can't use values from Part D.
From some info. available at net, i found that it has something to do with safety factor. Would highly appreciate respone in little bit more detail if this is the case.
Thanks,
Meck 91

 

[fegenbush]

SA-516 does not have letter grade numbers and is a plate spec.

Please correct, and I will try to assist as much as I can.

 

[Meck91]

Sorry, its a typo. Let's cnsider any grade of SA-516. All can be used in ASME Section VIII Div. 1 & B31.3.
Thanks.

 

[metengr]

but i would like to know the reason for this difference in allowable stress for material listed in both Secton II Part D & B31.3, for example Material SA 516 Gr. B can be used for Pressue Vessel as well as for piping but at all times if i am designing piping i have to use values from tables available in B31.3.

Each Standards Committee is charged with maintaining their code book. This means use of material, safety factors, welding requirements, fabrication requirements, service loads, and yes, allowable stresses.

 

[fegenbush]

I don't think I could have answered it better, metengr.

 

[stanweld]

The safety factors are different. 3:1 on UTS per B31.3 & 3.5:1 on UTS per ASME VIII, Div.1.