UG-27 & 28 Calcs for Finned Tube 1

[stanrick]

I have a finned tube made of SB-359 C12200 H55. The ends without fins are .745" OD x .047" nom wall. The unfinned ends are completely contained within the tubesheet. The finned portion is 0.611" ID x .028"nom/0.025"min wall, with .037" fins projecting according to the mfgr drawing. The fins are essentially a knurl, so I don't believe there is a stiffening ring effect.

Question: When doing Section VIII, Div 1, UG-27 & UG-28 calculations, is it proper to use the .611+.028+.028=.667 OD , or the manufacturer's nominal dimensions of 0.745 OD?

This seems like a no-brainer to me, but I've been wrong before.

Thanks.

 

[vesselfab]

what is the real (actual) diameter that is containing the pressure?

 

[unclesyd]

You can get two very good publications from Wolverine Tube on the use of finned tubes. The pdf's you download have links to each chapter or section in the index.

http://www.wlv.com/products/index.html

 

[stanrick]

The actual diameter that holds the pressure is the 0.611 ID X .028 Wall. As I said, this seems like a no-brainer. But more experienced engineers (no longer at my company) than myself chose consistently to use the outer diameter of the fins, rather than the outer diameter of the actual pressure-containing wall. I'm looking to understand the rationale behind this.

Also, thanks for the directions to the Wolverine website. There seems to be a goldmine of information for me.

 

[SnTMan]

stanrick, see UG-8(b)(4), Appendix 23

Regards,

Mike

 

[knstar]

as per UG-8(4)