The different assessment criteria between access nozzles and process nozzles in UG-45.

[mechengineer]

Hi Exsperts,

What is the consideration point for the different assessment criteria between access nozzle wall minimum thickness [ta] and process nozzle wall minimum thickness [maximum of ta,tb] in UG-45? Appreciate if the code committee members may reply. As I know there is no such difference in P.R China Pressure Vessel Code GB-150.

Thanks.

 

[SnTMan]

mechengineer, I can offer absolutely no proof, but I always thought the requirement was to insure some degree of mechanical strength to the process nozzles.

Regards,

Mike

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

 

[TGS4]

SnTMan is correct. Process nozzles have attached piping, which will give rise to nozzle loads. Additional consideration is required for those beyond just pressure containment. Hence the different rules.

 

[mechengineer]

@Mike and TGS4,
Many thanks for your response.
May I understand in this way? The difference is just becasue the external nozzle loads on the process nozzles and the code has no provided a detail mehtod to consider the extrenal nozzle load (like WRC297 or FEA). Instead of that, code gives the different rules in UG-45.
1. Can we say that the UG-45 has taken external loads into account? If meet UG-45, should not it be required to do the local stress analysis again?
2. Now using WRC538/297 or NozzlePro to check the nozzle external load is a general pratice in the pressure vessel design. In this case, whether we may ignore maximum of [ta,tb] as the minimum nozzle wall thickness by GU-45?
3. Doulbe considerations for the nozzle loads by both UG-45 and WRC538/297 verification. It's practicable but a bit confusing.
Thanks.

 

[TGS4]

1. Can we say that the UG-45 has taken external loads into account? If meet UG-45, should not it be required to do the local stress analysis again?

No and no

2. Now using WRC538/297 or NozzlePro to check the nozzle external load is a general pratice in the pressure vessel design. In this case, whether we may ignore maximum of [ta,tb] as the minimum nozzle wall thickness by GU-45?

No. The UG-45 requirements are mandatory, regardless.

3. Doulbe considerations for the nozzle loads by both UG-45 and WRC538/297 verification. It's practicable but a bit confusing.

Note that WRC 537 makes no consideration for the stresses in the nozzle (only the shell). WRC 297 does consider the stresses in the nozzle. The Code Committee has considered this and has determined, in their judgement, that this is a reasonable approach. As a member of the pressure vessel community, you are always welcome to disagree, bring your concern and alternative to the Code Committees for consideration, and discuss. We always listen and give due consideration.

 

[mechengineer]

@TGS4,
Thanks for the clarification.
Yes, I know that both WRC 538 and WRC 296 have no consideration for internal pressure. The design engineer shall consider it. Most software, like Compress and PV Elite, has considered both external loads and internal pressure.
Hope the Code Committees will give the typical method for nozzles local stresses analysis due to the external loads and internal/external pressure as per the current pressure vessel engineering practice in VIII-2 near future. After that, UG-45 may be simplified.
Thanks.

 

[r6155]

I agree with SnTMan and TGS4
UG-45 says "access openings and openings used only for inspection"