B75/B359 C12200 Finned Tube

[stanrick]

A manufacturer says his finned tube is "produced in alloy C12200 to meet mechanical, chemical, and testing requirements of ASTM B75/B359".

If I want to do Sect VIII Div 1 UG-28 calculations for this tube, do I use the External Pressure Chart NFC-1 or NFC-7 in Sect II Part D? (I am referring to lines 4 & 5 on page 186 of the 2008a addenda of Sect II, Part D.)

Thanks,
Rick

 

[gr2vessels]

I don't have yet a copy of the 2008 addendum to Sec II-D, but unless the addendum declares the ASME II-D null, void and totally obsolete, including ASME VIII, then the UG-28 remains valid and applicable to your tubes, including also the external pressure charts. I'm sory, I could not comment on the misterious lines 4 and 5 of addendum.
Cheers,
gr2vessels

 

[doct9960]

stanrick,

A manufacturer says his finned tube is "produced in alloy C12200 to meet mechanical, chemical, and testing requirements of ASTM B75/B359".

I guess what your manufacturer is saying is that he can provide you with 2 classes of finned tubes:
1. tubes with integral fins that meets the requirements of ASTM B359;
2. tubes with non-integral fins where the tubes meet the requirements of ASTM B75.
(If the finned tubes are for ASME VIII-1 construction, the material designation should be ASME SB-359 or SB-75)

If I want to do Sect VIII Div 1 UG-28 calculations for this tube, do I use the External Pressure Chart NFC-1 or NFC-7 in Sect II Part D? (I am referring to lines 4 & 5 on page 186 of the 2008a addenda of Sect II, Part D.)

For SB-359 Alloy C12200 Temper H55 or O61, use External Pressure Chart NFC-1.
For SB-75 Alloy C12200 Temper O50, use External Pressure Chart NFC-7. If the Temper is H55 or H80, use NFC-6.
(My above reply is based on the 2007 Edition of ASME II Part. I still don't have a copy of the 2008 Addenda. Check your 2008 Addenda and see what it says there.)

 

[stanrick]

Thanks for your responses, gr2vessels & doct9960. For what it's worth, I also got some feedback from the tube manufacturer. According to UG-8(b)(4), I need to do internal & external pressure calculations for both the finned and unfinned portions of the tube. The tube manufacturer tells me that I should use SB359 C12200 H55 for the finned portion, and SB75 C12200 050 for the unfinned ends of the tube. (I suppose this is because the process of forming the fins changes the material properties.) He also point sou that the Code is conservative, and that many people will opt for Appendix 23 and UG-101 tests instead of the calculations.

This is consistent with the guidance provided by the folks who certify our facility. Namely, the UG-27 & UG-28 calculations were developed for simple cylindrical bodies under pressure. Once you start adding fins (which I suppose can either be stiffeners or stress-concentrators) the calculation results lose accuracy, and actual test results become the more reliable method for finding allowable pressure.

All of this is quite interesting, and I am grateful to those who help enlighten me to the many intricacies of the code.

Rick