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Hello all, I need to evaluate shell stresses at a nozzle attachment on a pressure vessel. PD5500 requires that the distance between the end of the cylinder and the edge of the attachment should be not less than r/2. Where 'r' is the radius of the shell. In my case the nozzle is less than r/2...

Codeeng, Thanks for your posting. As far as the code goes, I think you are correct. Would you suggest I consider the hoop stress on its own then, without combining it with any other stresses?

Thanks everyone. I guess I should summarise the basis for my investigation. ASME B31.3 is concerned with stresses due to the following four load combinations: 1. Hoop stress (due to Max P)- this is coincident with the max temperature. 2. Sustained (due to Gravity + Max P) 3. Expansion (due to...

Thanks everyone. I guess I should summarise the basis for my investigation. ASME B31.3 is concerned with stresses due to the following four load combinations: 1. Hoop stress (due to Max P)- this is coincident with the max temperature. 2. Sustained (due to Gravity + Max P) 3. Expansion (due to...

metengr, Thanks for your input. The pipe is designed to ASME B31.3 which has its own allowable stress tolerances different from ASME B&PV sect II. The allowable stress in B31.3 starts dropping from 400deg F (204deg C). I'm not concerned about accelerated corrosion. You see, the pipe is under...

codeeng, jt, Thanks for your input. Jt, you are correct. The pipe is under longitudinal compression and that's what complicates the matters. Under the combined load (pressure, longitudinal force, gravity, occasional load, etc.) the combined stress is higher than the code allowable. However, the...

Hello all, We are trying to assess fitness for service of a A106-B, 30 inch refractory lined pipe which is opearting at its max design conditions - 23barg (MAWP) and 150deg C temperature (designed to ASME B31.3). Thermographic examination has shown several hot spots of 200 to 270deg C. Is there...

Hello all, We are trying to assess fitness for service of a A106-B, 30 inch pipe that was originally designed to operate at 23barg MAWP and 150deg C temperature (to ASME B31.3). The piping is currently running at the max design pressure and temperature. Thermographic examination has shown...

Someone was quick to insert a (commercial) hyperlink into my thread. So annoying!!! Anyway, I've just found some inconsistencies in Appendix P.3. I hope jt will be able to comment. The "Upper limit (u)" presented in Tables P-2 through P-4 contain some errors. Some of the graphs representing the...

jt Thanks a lot for advice. That's exactly what I did - interpolated twice. As soon as I had a good look at the graphs it all made sense. However, I found that the “u” value for one of my nozzles was marginally outside the upper limit of the graph (one of the two). The graph ends at u=1 and my...

Hello all, Appendix P.3 (2003 addendum) now allows to evaluate stresses at nozzle-to-shell intersections due to external nozzle loads. Tank parameters (d/tn), (t/tn) and (u) determine equations (or curves) for calculating the stress factors. The three sample problems given in the code deal...

Arto, Many thanks for your input. However, Div 1 provides design by rules, not by analysis. Section 1-7(b)1 states that “the rules…do not include any analysis for stresses resulting from externally applied mechanical loads”. Div 2, on the other hand, is design by analysis but the dimensional...

Hello all, Can someone please advise what calculation procedure to use for evaluating stresses at nozzle attachments larger than half the vessel diameter? There is an existing shell & tube heat exchanger designed to ASME VIII Div 1. It will experience uplift in a seismic event thus causing...

codeeng, Thanks for your input. I just want to know what method caters best for large round attachments. If PD5500, Bijlaard or WRC 107/297 don't cover d/D>0.5 then what does? FEA is not an option as we don't have any in-house FEA software. Have to do it the good old manual way.

Hello all, Can someone please advise what calculation procedure to use for evaluating stresses at nozzle attachments larger than half the vessel diameter? There is an existing heat exchanger that was designed to ASME VIII Div 1 in the fifties. It will experience uplift in a seismic event thus...

Hello all, Can someone please advise what calculation procedure to use for evaluating stresses at nozzle attachments larger than half the vessel diameter? There is an existing heat exchanger that was designed to ASME VIII Div 1 in the fifties. It will experience uplift in a seismic event thus...

MJC, Thanks for your input. The tanks have been in service for over ten years now and the reason why we are checking the nozzle attachments is that the owner is now making some dramatic alterations to the pipework. As I mentioned above the tanks experience a lot of vertical movement due to...

Hello all I need to back check the design of an existing storage tank fitted with a pressure relief vent and a vacuum breaker (set at 5kPa and 0.5kPa respectively). This is outside the scope of ASME VIII Div.1 (External or internal pressure not exceeding 15psi). It is a vertical cylindrical...

jte, pmover, Many thanks for your input. We've just been told that the second tank (question 2 above) will be fitted with a pressure relief vent and a vacuum breaker set at 5kPa and 0.5kPa respectively. This is outside the scope of ASME VIII Div.1 (External or internal pressure not exceeding...

Hello all, I have two questions: 1) There are two existing bulk fuel storage tanks that require nozzle load checking. The tanks were originally designed to API 650 but it appears that no calcs were ever done for the max allowable nozzle loads imposed by the piping. The tanks experience a...