A105 Lap joint flange limitations 1

[vipereng]

I have a question regarding the use of A105 / Aluminum Lap Joint flanges according to B31.3 in the following arrangement.
Design Temp: -320 deg F
Design Press: 100 PSIG

The actual 'stub end' of the connection is Aluminum (B247 6061-T6), the A105 portion is the backing flange that doesn't come in contact with the actual -320 process, it's only being used to mechanically connect the aluminum stub ends.

According to B31.3 where will I find this arrangement to be acceptable or unacceptable?

thanks in advance..

 

[stanweld]

Other than eliminating A-105 from -320 F consideration, B31.3 will not provide the info requested. The designer determines the design temperature conditions. If the Aluminum alloy stub ends experience the cryogenic temperature, you can be assured that the connecting flanges will as well. And, if so, your selection of material is inappropriate.

 

[racookpe1978]

Why would you expect the aluminum flange NOT be at your process fluid temperature within a few seconds of filling the pipe -320 degrees conducts through very, very quickly.

 

[TWP]

Follow the rules of ASME B31.3. Use Table A-1 for all individual pipe & flange components, incl. bolting. Gasket mat'l also to be checked.A105 is surely not suitable. Consult also ASME B31.3, Appendix L. Regards. Th Pl

 

[XL83NL]

Why not keep it simple and use an A182 F304/L as the backing flange? Unless you're dealing with a lot of flange connections (maybe in larger sizes) the added cost of F304 vs A105 may provide to be beneficial compared to additional engineering and testing when applying A105 flanges.
Furthermore, if the backing flange really gets around the design temp of -320 F, you'll know for sure A105 wont hold it.

 

[StressGuy]

At this point, wouldn't you guys think he'd be better off with a full weld neck flange? I can understand a lap joint when you need something exotic to handle the corrosive nature of a process and can then use cheaper carbon to give the mechanical strength for the connection.

Yet, as everyone else has observed, that's not going to work in this case unless the OP has discovered some heretofore unknown perfect insulator to slip between the stub and flange.

It's probably worth seeing the cost difference between and aluminum/ss lap joint combo vs. a full aluminum weld neck.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.