It is true that Annex W does not compute the membrane stress at the attachment edge. In the same time, I think it is clear enough that Annex G considers that the membrane stress contains intensified stresses due to the presence of the hole. However, by engineering background, one can remember that this may be necessary when the subject is fatigue, but may not be necessary where this condition does not obtain.
This is confusing and contradictory and in my opinion Annex W is wrong just because does not follow the "spirit" of Annex G of PD 5500 and the missing calculation brings unsolved questions. But adopting the concept of stress concentration factor give you the opportunity to be on the safe part, isn't it? and this is one argument that cannot be ignored.
I guess that's why in PV Elite Coade/ Intergraph put the option to check the membrane stress at edge as an attempt to solve this endless dilemma- must be checked? may be missing?
To check it, you must activate Print the membrane stress. You are right- this is confusing, too (I mean it seems that my choice would be to print it rather than to compute it)- but is the approach of Coade/ Intergraph to put software options in a strange ways and places... at least this is my perception.
Only a guess about your consultant.... For many years the primary method for computing the stress in nozzles that have a mechanical loading has been WRC-107. The stresses computed with this procedure were then compared with the ASME Code allowables. WRC-107 does not classify the stresses. General practice in many industries has been to compare only the Primary plus Secondary (P + Q) Stress Intensity due to the mechanical loading to 1.5Sm. While the membrane stresses are computed, they are not always compared separately with the 1.5Sm criterion. Maybe your consultant was so immersed in this approach that he/she tends today to extend it automatically to PD 5500!
What I try to say is that an educated and old enough engineer may be reluctant to enthusiastically adopt the concept of Stress concentration factor at the attachment edge just because for many years limiting only (P + Q) Stress Intensity as per ASME was satisfactory when worked with WRC, while checking the local stress may be missing.
And a final question... Why one would think that considering a PD5500 concept that is close to fatigue subject shall address a real issue, whereas the same PD 5500/W does not calculate it for a regular case?
But it may be something more than I tried to guess. Your consultant may have a deep knowledge on some articles and/ or may have experience on FEA works.
Recalling ASME now (because the reader would be more familiar with), it is clear that well away from the nozzle the General Primary Membrane stresses in both the shell and nozzle are to be below Sm. In fact, as a measure of how close to the nozzle we can be before the membrane stress is allowed to exceed Sm, we can take guidance from ASME Section VIII, Division 2 Appendix 4, where there is the definition for Local Primary Stress. So beyond the limits of Local Primary stress, the General Membrane should be kept below Sm and this is a valid rule. But for Local stress, it is the exception rather than the rule when a conventionally designed nozzle will meet the local membrane criterion (1.5Sm) at the junction-ring if the bending loads are included and for this reason so many engineers are happy accepting the status-qvo. Simply said, this criterion is told to be inappropriate and must be replaced with something more realistic. Or we may accept it keeping in mind is conservative.... The same may be said about PD5500 and the reference to ASME I've done is for similitude only.
In the end I will mention a paper which has the title A Proposed Method for Finding Stress and Allowable Pressure in Cylinders with Radial Nozzles. It does not bring light to your query but it is interesting to know it for "historical" reasons. PVP-399 is a ASME Pressure Vessel and Piping conference publication and is from the 2000 presentation. Therein was Mr. Bildy’s first presentation of an alternate analysis method for nozzle openings. This paper was later adopted as a Code Case for the ASME Boiler & Pressure Vessel Code (Code Case 2398). And Code Case 2398 was later adopted into ASME Boiler & Pressure Vessel Code Section VIII Division 1 as Appendix 1-10. Moreover, Code Case 2398 was later adopted into the ASME Boiler & Pressure Vessel Code Division 2 "rewrite" of the 2007 Edition. It is available at [link Point to another website Only the registered members can access]
A valuable guidance more linked to your case may be found on [link Point to another website Only the registered members can access]
My best regards.
Marian
PS I am not fighting for a gift, it is just an attempt to answer giving my understanding on your query. I'm sure that, when you'll conclude that is worth to upload PD 5500 - 2015 you will proceed in this way, giving the gift to everybody.
Thanks to you and many others (I just hope that I do not offense them not mentioning their names!) we have access through a prohibitive turnpike of engineering, where "the Corpogods" ask for incredible high amount to access by. True, they must sustain their activity but when put such pressure of pecuniary difficulties on engineering shoulder must recall in mind the Laffer curve (or in words "increasing taxes does not increase revenue"). True again, this sentence is not to legitimate infringing copyright and it is not a moral matter to be solved in this forum.
Actually, what I want to say is just "Thank you again" because what you folks uploaded here help me improving my engineering knowledge.
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