Appendix 1-7 calculation

[McJe]

Hello,

I do not understand the definition of the limits stated in appendix 1-7 of the ASME code. It seemes there are 2 different limits of reinforcement used for calculation of formulas (1) and (2) of 1-7(b), and formules (3)-(4)-(5) of 1-7(b) which also differ from the limits used in UG-37.
I tried some hand calculations, and I get different values then I get from our old DOS-calculation program and from an example calculation I found on the internet (not from Compress). The 2 examples I wanted to check my calculation against, are also not compatible. So I now have 3 different interpretations of the code.

I would like to ask if someone would like to send me a Compress calculation of a large opening, calculated with appendix 1-7. All I would like to see in the calculation is a shell and a large opening + nozzle, and it's calculations.
It would be nice to have the metric values. The PDF output would be very nice.

We do not have Compress over here at this moment, but we are evaluating several options. Our boss still needs to decide which software he will buy.

Thanks a lot!
Jeroen.

 

[PeeVeeGuru]

I found this on Codeware's website:

Question:

How does COMPRESS determine which nozzles fall under the category of "large openings" subject to the rules of Appendix 1-7?

Answer:

For shells under 40" diameter, UG-36(b)(1) specifies that rules for reinforcing of nozzles per UG-36 through UG-43 apply to openings not exceeding one-half the vessel diameter.

Appendix 1-7(b) applies to nozzles that exceed the limits of UG-36(b)(1). We interpret rules (a), (b), and (c) of 1-7(b)(1) to apply individually (ie: a nozzle meeting any of these size criteria must meet the rules of Appendix 1-7(b)(2),(3), and (4)). If the nozzle Rn/R also exceeds 0.7 as specified in 1-7(b)(1)(c), COMPRESS performs the stress analysis of Appendix 1-7(b)(2),(3), and (4) and then reports that the Rn/R ratio exceeds 0.7 and additional analysis is required per U-2(g).


However, I believe this document is not up-to-date with the analysis performed for large openings with ratio of radii greater than 0.7 . Currently, when Rn/R exceeds 0.7, compress will perform the Appendix 1-10 or Division 4.5 analysis even if the checkbox to perform section 1-7 analysis is selected.

 

[PeeVeeGuru]

More of an answer to OP's question:

The analysis of a simple case of a nozzle is summarized below:

1) Use UG-40 to calculate the limits of reinforcement both in the parallel and outer normal directions(inner limits not supported by 1-7 last I checked).

2) Area available per UG-37 is calculated, summed, and compared to 'A' required from the same section.

3) Next the opening is checked per 1-7. Now only 2/3 of A from UG-37 is required, but it must lie within 75% of the parallel reinforcement limits from UG-40. Essentially A_1 is re-calculated by replacing d with (2*parallel-UG-40-limit - d) in the equation shown under fig UG-37.1 for case b.

4) Now the modified area that was calculated is compared to 2/3 of A from the second step.

5) This is where I think you are confused? -- the 2nd term in the calculation of Sm is not [t + t_e + sqrt(Rnm*tn)], but rather [t + smaller(t_e + sqrt(Rnm*tn), Lpr] where Lpr is the distance the nozzle protrudes from the vessel surface, and I believe this may also be limited by an attached flange. Calculate Sb as well.

6) Finally check your allowables...

Note that I skipped summarizing any weld requirements above and there seem to be different code interpretations especially for the more complex nozzle configurations, so I would recommend contacting Codeware's customer support directly to discuss a specific sketch if you still have questions.

 

[McJe]

Thanks for the explanations.

Nevertheless, if someone should have some spare time, I would be very interested in a Compress output pdf of such a large opening. In this way, I can easily check my calculation spreadsheet against the output Compress generates.

Jeroen.

 

[DeZego]

Jeroen,

My company doesn't use COMPRESS anymore, but we now have a program called PVElite, by COADE. I recently used PVElite to analyze a large nozzle, so I have attached a PDF of the calculations. Hopefully it will shed some light on Appendix 1-7 for you; it certainly helped me.

My only caveat is that I am not sure the program correctly calculated the available area in the shell for 1-7(a). The program is using the smaller of the two limits defined in 1-7(a)(1). The 2001 version of the code says to use the larger of the two limits, but I don't have the 2007 code so I don't know if that has changed.

Richard DeZego, Jr.
Mechancial Engineer
www.bisfei.com