nozzle bore

[picasa]

In a refinery setting, is it typical for the bore of pressure vessel piping to match the bore of nozzles to which the piping is connected? Nozzle schedule is determined per code based on design conditions and external loads etc. Does piping schedule need to be changed to match the nozzle bore? What does code say about this issue? If nozzle bore is smaller (wall thicker) can you taper it down to pipe bore to match it?

Are there any other considerations on this issue? Like type of flow, type of fluid, pressure, temperature etc.?

 

[codeeng]

Its pretty normal for the nozzle to be thicker than the attached piping due to Code minimum thickness requirments. This small step should not be an issue since the pressure drop would be the equivalent of typically one extra fitting. Note that the vessel Code does not cover attached piping.

 

[jte]

codeng's response is right for flanged connections (which is probably 99% of the connections). The only time I'd demand matching the bore is for a welded piping to nozzle connection in which case I'd have the (thicker) vessel nozzle tapered to match the (thinner) piping per VIII-1 UG-13(g).

jt

 

[codeeng]

jte, where does UG-13 come from? I'm not sure where its specified but as I recall taper boring would not be required where the difference in wall is less than 1/8".

 

[jte]

Ummm... would you believe UW-13?

jt

 

[CodeRef]

Codeeng, you are thinking of UW-9(c)? (tapered transitions)

..............A tapered transition having
a length not less than three times the offset between
the adjacent surfaces of abutting sections, as shown in
Fig. UW-9, shall be provided at joints between sections
that differ in thickness by more than one-fourth of the
thickness of the thinner section, or by more than 1?8
in. (3.2 mm), whichever is less..............

for transitions to piping attached to ASME Code Vessels, follow the Code specified for the piping, and for transitions within the scope of the vessel (ASME Sec. VIII), the transition may be formed by any process that will provide a uniform taper and alignment should be that specified in table UW-33. Use good engineering practice for the piping to nozzle connection if not specified in a code and that would suggest a taper bore in my opinion.