Minimum required thickness for nozzle

[karta013]

Dear all,
i am new here, please kindly to give your suggestion and guidance.
I am a little bit confuse about " minimum required thickness". Generally in shell and head calculation, the minimum required thickness is design thickness minus corrosion allowance, is that also same with wall thickness for nozzle or not? because in UG-45 stated that the thickness is for "minimum required thickness", so if i already get the thickness based on UG-45 in ASME code sect VIII div.1, is that means the thickness is minimum required thickness or just required thickness (same wit design thk)? if that value same with design thk i guest that i have to calculate that value minus corrosion allowance to get the minimum required thickness. So the point of my question is: is the thickness mentioned in UG-45 : design thickness or minimum required thickness.
i need your help to corrected of my understanding in this matter.
Thank you.

Regards-Karta

 

[racookpe1978]

I may be mis-understanding your words, but they seem incorrect.

Calculated wall thickness comes from pressure, service limits, metal choice, and the Code factors, primarily diameter and margins.
Minimum PV wall thickness is calculated wall thickness PLUS corrosion allowance PLUS wall fabrication (mill) tolerance.
Minimum Pipe wall thickness is almost always less than minimum PV wall thickness because the pipe diameter (nozzle diameter) is smaller than the vessel diameter.

Once every wall thickness and diameter is chosen, then you MUST go back to each nozzle and determine if the "opening" in the PV wall requires "additional reinforcement" around the opening to maintain vessel strength. Often, no additional reinforcement around the nozzle is needed. But you cannot make that assumption without checking.

 

[Jano6924]

Required thickness comes direct from ASME VIII-1 formulas, Design thickness is required thickness plus corrosión allowance added, nominal thickness is the thickness commercialy available. Yes, for pipe the mill tolerance shall be considered. See Appendix 3-2 for "definitions". Mínimum allowable thickness may come from UG-16(b) for example.

As racookpe1978 states, for nozzles you must check if each opening requires additional reinforcement, that will depend on design conditions and size of opening (nozzle). The fact is that UG-45 gives you the "mínimum required thickness" for a nozzle neck which may be, or not, enough for opening reinforcement.

Hope this helps.

 

[SnTMan]

Regardless of all other considerations, the nozzle shall not be less that the UG-45 thickness.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[karta013]

Dear all,thank u for your explanation, i think thickness in ug45 is same with design thickness since it contain corrosion allowance in it's calculation. So if i want to get the minimum required thickness, i have to exclude corrosion allowance from calculation, am i right?