When I perform a calculation for large nozzle (diameter nozzle ≈ diameter shell) with the option "Use Appendix 1-10 instead of UG37" turned of, but with the "Asme large nozzle calc option" on "use 1-10" than the results for “results of nozzle reinforcement area calculations” are given for both the design as the external situation.
If the option "Use Appendix 1-10 INSTEAD OF UG37" is turned on with the same nozzle input I get to see only the external results.
In my opinion both calculations are based on Appendix 1-10 and should therefor give identical results. Why do I get in one case the design results, and in the other case only external results?

if nozzle diameter/ vessel diameter is greater than 0.7,then Appendix 1-10 does not apply, Beyond the scope of Appendix 1-10.

UG-2 (g) should be used to carry out stress analysis.

Thank you holizhang, but I don't understand your answer. The code says (asme 8 div 1 2015): Properly reinforced openings in cylindrical and conical shells are not limited as to size except with the following provisions for design. The rules in UG-36 through UG-43 apply to openings not exceeding the following: for vessels 60 in. (1 500 mm) inside diameter and less, onehalf the vessel diameter, but not to exceed 20 in. (500 mm); for vessels over 60 in. (1 500 mm) inside diameter, one‐third the vessel diameter, but not to exceed 40 in. (1 000 mm). (For conical shells, the inside shell diameter as used above is the cone diameter at the center of the opening.) For openings exceeding these limits, supplemental rules of 1-7 shall be satisfied in addition to the rules of this paragraph. Alternatively, openings in cylindrical or conical shells exceeding these limits may be designed for internal pressure using the rules of 1-10 [see (c)(2)(-d)].

In my case I exceed this limit and therefore I should use Appendix 1-7 or 1-10. I used appendix 1-10 with the results as mentioned above.

Hello Ruzel

The limit on size as stated in UG-36 is a rule. Let me explain the issue. As you may recall, a cylinder subjected to internal pressure experiences two stress. One is the hoop stress, and the other is the longitudinal or axial stress. I happens that the hoop stress magnitude is twice that of the longitudinal stress. This causes the nozzle to 'open up' in the hoop direction and try to go into a conical shape. Now, in the case of a nozzle in a sphere or head, you can have a nozzle of any size. Why? Simply because the stress are the same in all directions.

When I was a vessel engineer in South Africa, I actually had a nozzle open up on me, because I did not take the necessary precautions in performing the review of the design. The warning in UG-36 is there for a very good reason, and extreme caution should be exercised in designing large nozzles in cylinders. Another note of caution: Never design a protruding nozzle when it is considered as being large. Very large distortion stresses can be the result.

Thanks, I understand the reason of this limitation. In this case there will be no big problems with this. The vessel is in use for many years in similar shape without any problems. It is more or less an equal Tee.

But i didn't understand the reason of the difference in the output.

After a lot of comparing I understand the differences. Where I thought that the calculation should be equal in fact it isn't. appendix 1-10 is only for internal pressure, so in my case there is external pressure also. The table i have mentioned in my question is meant for the results from UG-37. In this case only the external pressure. the internal pressure is therefor not mentioned in the calculation. The other option calculations internal according to UG-37 and Appendix 1-10 and the external according to ug-37 therefore the table includes the design values.

Hi Ruzel

When a vessel has been in service for many years, that is proof enough. However the ASME Division 1 comprises rules, and you have to adhere to them. Division 2 allows the use of stress analysis, but that is going a bit far. A solution I have used is to insert tie bars inside the opening that act as bridge pieces to stich the sides of the hole together, but is not in accordance with ASME. The bars are placed in the hoop direction.

If you are designing a new vessel, that is the problem.

see figure

Hello Holizhang

I am not familiar with that diagram. Remember, the code does not give us the stresses in any particular situation. Rather, it has a rule that represents stress without really giving the actual stress. There is no method that can do that. For example, we have a formula for the hoop stress in a cylinder in ASME VIII, Division 1. That is not the stress that exists in a cylinder. The stress field is far more complicated than that.

What am I getting at? Simply this: Follow the rules that have been in existence for over 90 years, and we can stay out of trouble and sleep at night.

We can make diagrams, but they give only a vague idea of what is going on.

1.See ,(Dennis R.Moss and Michael M. basic) for details.

6: Special design.............................................393
procedure 6-1:design of large-diameter nozzle openings........394

Hello Holizhang

We have strayed far from the original narrative. The subject is large diameter nozzles. In my opinion I covered the principles that govern the restrictions. Engineering should be as simple as possible, and ASME Division 1 meets that criterion. The rules are easy to apply, and achieve safe results.