ASME B31.3 "Hill side connections" & ASME VIII Div 1 3

[Clareok]

Scenario: Design Code B31.3. Branch connection to pipe run is hill side.

Code Clause: 304.3.1 (b) (4) “the axis pf the branch intersects the axis of the run”

Problem: B31.3 does not consider hill side branch connections.

Solution: Refer to 304.7.2, but this does not allow calculation to ASME VIII Div 1 which would be the logical method.

Can someone please tell me why one cannot use UG-37 (VIII, Div 1), understand 31.3 doenst allow it, but why?

Surely this is a common connection in the industry with no simple solution?

 

[moltenmetal]

Some would argue that B31.3 is a rules-based code, so you must follow the rules- period- even when they essentially say "you can't design something which meets the functional requirements". I'd argue that this is giving the code a little too much credit. It is not intended to eliminate the need for engineering judgment- it is intended to set rules of good practice and to permit people who do not have sufficient engineering judgment to build piping that is more or less safe.

Practical people know that the rules which render an ASME VIII-1 pressure vessel safe, can also be applied to the design and fabrication of piping- not blindly, but judiciously with proper engineering judgment and commonsense.

B31.3 doesn't distinguish between a piping branch connection, which must remain safe against potentially very large forces and moments which may be applied on the run pipe by that piping branch, and a non-moment instrument or tubing connection. ASME VIII does make this distinction, allowing instrument branches to be designed differently.

Speak to the owner- I have met few owners who will not permit special connections in piping to be designed and fabricated per ASME VIII. Our own specs spell this out in detail.

 

[XL83NL]

Excellent post mm, a star for you. Do you have a reference to the relevant VIII-1 section that differentiation for instrument (nozzle) connections?

 

[moltenmetal]

ASME VIII-1 UW-16(f)(5) and (6) give the circumstances under which a standard fitting such as a half coupling or flange may be attached to the wall of a vessel by means of a single fillet weld made from the outside. That these connections will be used for the connection of instruments, tubing or the like (which will not transmit substantial moments to the connection) is not spelled out in the language of the code, but it is certainly implied in the nature and limitations of the rules.