B31.3 Flange Issue

[anolan23]

Nowhere in the B31.3 code does it state that I cannot directly attach a B16.5 WN flange to an extruded outlet header. Can I get away with omitting the branch pipe that would typically be used between extruded outlet header and flange?

 

[TGS4]

As you said, such a configuration is not prohibited. So...

 

[anolan23]

Thanks for your input!

 

[pennpiper]

How many times will we be required to answer this same elementary question?

Any Flange or fitting can be directly welded to any other Flange or fitting providing they are both the same NPS (the same OD and ID within reason). In this case the Extruded Outlet Branch takes the place of a TEE fitting.
A pipe pup piece is NOT required between your Extruded Outlet and the Flange (unless you need a specific stand-off dimension).

Sometimes its possible to do all the right things and still get bad results

 

[anolan23]

Ok. Now that I know that I can do the above, how does this affect the 304.3.4 Reinforcement calculations?

Am I right to say that A₃ will be zero since there is no branch pipe now?

What about A₄? Since there is no thickness of the branch, T_b, is A₄ not calculable? THANKS

 

[KevinNZ]

Pennpipers reply applies to welding WN flanges to fittings. But welding SO or SW flanges to fittings is more difficult as the part of the fitting that you are welding to may not have parallel sides.

An extruded outlet reinforcing calculation uses part of the extrusion and part of the attached pipe for the calculation of A3. Since you would only be welding a WN flange to the extrusion I would use part of the flange weldneck in the A3 calculation.

 

[MJCronin]

anoland....

IMHO, the phrasing of your question, reveals another deeper problem

Somehow, the perception of all US Codes and standards has incorrectly shifted from "a book of approved criteria, materials, methods and recommendations" to one of "a list of things that I can't do".

This prompts angry questions such as "Show me where in the code it says that I can't do X ?????"

This is a fundamental misunderstanding of the nature of the document.....

While ASME B31.3 Piping Code contains some limitations on material usage, pressure ratings and the like, it is primarily a book of approved and time tested methods of design, fabrication, inspection and testing.

Anyone else ?

MJCronin
Sr. Process Engineer

 

[anolan23]

Thank you KevinNZ,

when calculating t_b in A₃ (the pressure design thickness of branch), do I calculate this as a straight pipe even though it is a WN flange?

 

[anolan23]

Anyone? This is a hot topic for me right now