minimum thickness for nozzle necks

[simchuck]

I do not have access to the BPVC itself, but I do have a summary in an engineering text which describes the criteria for required thickness of a nozzle neck as the largest of:

(1) the thickness computed from the loadings (internal pressurization, reactions, etc.) plus an allowance for corrosion

(2) the required vessel wall thickness (based on E=1) plus an allowance for corrosion

(3) the minimum thickness of standard pipe (considering a 12.5% manufacturing tolerance) plus an allowance for corrosion

(4) 1/16 in (1.6 mm)

Can somebody tell me whether this information is accurate, and if so, what is meant by the second criterium? It seems to suggest that the nozzle thickness is affected by that of the larger pressure vessel, although this does not seem intuitive.

Thanks

 

[Christine74]

That summary is <i>close</i> to what Sect. VIII-1 requires, but it's not quite correct.

The nozzle necks must be at least as thick as the values found in (1) and (4), but they only need to be at least as thick as the <i>smaller</i> of the values computed in (2) and (3).

What I've described above is for vessels under internal pressure only.

-Christine

 

[WBH]

Consideration must also be given to the material stress values and appropriate temperature for the stress values. Higher temperatures will reduce the stress values for the selected material, with an increase in thickness required. Stress values will be different for various components of the same material.

Minimum nozzle neck thickness can not be derived from internal pressure calculations alone (see UG-22 for loadings) proper reinforcement of the nozzle opening must also be provided by either additional nozzle neck thickness, weld size, reinforcement pad or combination of the above (if requred by calculations)

See UG-36, UG-37, UG-40, UG-41 and UG-45 regarding minimum wall thickness of a nozzle neck and reinforcement of nozzle openings. If possible you need to reference Section VIII Div. 1 to ensure the thickness of your nozzle neck will meet requirements.


WBH

 

[deanc]

The first two replies have addressed this well. If you notice they both address Code paragraphs.

A caution here for a student. Never work from memory. Never do your actual work from references other then the Code,unless you can refer to U-2(g). Always use the currnt edition and addenda. See U-2(e)the AI may ask how you arrived at your answers. Be ready to back up any of your work.

 

[deanc]

A lighter note-have a look at UW-16. What is a fitting? Can it be a piece of pipe machined to a socket on one end? If so,what is the min. wall of the nozzle required to be? Refer to the interps. before you anwer. Have fun.