I think this has drifted slightly off topic. I am not looking to justify single run + error = accurate solution.
If the solution, to the problem on which you are working, is to be compared to a limiting stress then would it not be a reasonable approach to use the error estimation to estimate an...
There is always a simple practical answer. I don't subscribe to the notion that design by analysis methods must involve any black art/touchy feely/mumbo jumbo techniques. From what you suggest I think that the ERR option is somewhat redundant. Mesh convergence is the tried and tested method. I...
Can anyone explain to me the basis of the stress error when plotted using the ERR option.
Specifically, is this reporting the error in the energy norm or a more tangible error such as actual "stress" or a percentage error?
I can't find anything in the user manual that explains this.
Kenyi,
Some of the openings on the header look to be quite close to each other. You may also need to check mutiple openings for interaction. Does this system operate at elevated temperature? If yes then the expansion stresses may be a controlling condition.
Kenyi,
If the purpose is fluid collection and onward transmission it sounds more like a piping application. If the design limitations in ASME B31.3 304.3.1 are exceeded then the alternatives in 304.7.2 (additional stress analysis/proof testing) would be painful so I would agree with CodeJackal...
This "head" sounds more like a header as it's 10m long.
Kenyi, you seem to be looking for a suitable application standard. It would help us to understand more if you could describe the equipment that you are designing and its purpose/application. Is this a pipework system or perhaps a boiler...
CodeJackal,
Thanks for all your your input. I believe that your suggestion to remove the debatable item from the ASME VIII scope is the best plan. The AI, after discussing the point, is as much a victim of code clarity as the rest of us and interpretations take more time than is commercially...
Thanks for the quick response CodeJackal. The main question related to the minimum thickness required by UG-45 and in particular the reference to Note 25. If a tube is supplied to a specification that, for the sake of argument, lists 0.06" as the standard thickness for a particular diameter does...
The footnote to UG-45 refers to a material specification that does not use schedule weights acc. to B36.10M. In this case the specification's own 'regular' pipe weight should be used as the minimum thickness even when less than standard weight pipe.
This may be a stretch but can this be used...
Can I suggest the following:-
1) Use a design procedure for cylindrical shells under external pressure (e.g. ASME VIII Division 1 Section UG-28, PD5500 section 3.6).
2) If this is not suitable use another recognised method (e.g. Roark's Formulas for Stress & Strain, 6th Edition Table 32) but...
Thanks for that link unclesyd.
The 20/30 year old designs you mentioned are interesting. I believe that wind or seismic loading and its effect on the nozzle reinforcing calculation is easier to consider today due to developments in available software.
The 1979 revision of WRC107 included Appendix B - Stress Concentration factors for Stresses due to External Loads. This Appendix has curves for the evaluation of Kn & Kb values.
Also, you may find the WRC107 article published in the COADE June 2000 newsletter useful. You can find this at...
Thanks for the quick responses,
prex - we are in agreement.
warrenw - as a design consideration, yes, wind and pressure would be taken as concurrent loadings. This thread is a code interpretation question more than anything else. The 1/2" requirement comes from the formula t=(0.5PR+F/S-0.5P)...
I would be grateful for any opinions/experience on this issue.
In the design of tall towers/columns it is possible that either wind or seismic loading will induce longitudinal stress levels in the shell which can control the shell thickness. Within ASME VIII Div 2 this is covered in section...
