Posted by: leehc
PD5500 - Annex G (Local Stress Analysis) - 03/18/04 07:12 PM
Dear Sir,
I have another question here. For "hub and self-reinforcing" selection, I notice that the PVElite is concerning the nozzle neck thickness for nozzle OD instead of the nozzle hub thickness for calculation. In my opinion, I think that the calculation should base on hub thickness for nozzle OD since this is the portion that contact between nozzle and shell. Please correct if I am wrong.
Thank you.
Regards,
Lee
Posted by: Scott_Mayeux
Re: PD5500 - Annex G (Local Stress Analysis) - 03/22/04 05:04 PM
Dear Lee,
You are indeed correct. Look for a build annoucement later this week. This problem has been corrected and will be reflected in the March build of PVElite.
Posted by: leehc
Re: PD5500 - Annex G (Local Stress Analysis) - 03/24/04 01:49 AM
Dear Scott,
Actually, I have a major problem with Annex G. The load given seem like failing all my vessel. I have to increase my vessel thickness around 10mm. I have try to use the same load on WRC107 and my current vessel thickness is ok. This Annex G really conservative and killing me.
Is there any loop hole in Annex G that I can make it less conservative? In para G.2.3.6.1 note 6, it stated that the pressure has been omitted for simplicity. Is that mean I am allow to ignore the pressure in local loading calculation? Please advice. Thank you.
Posted by: Ray_Delaforce
Re: PD5500 - Annex G (Local Stress Analysis) - 05/21/04 08:21 AM
Hello leehc
To get a better handle on the problem, it would be good to send me the file at: support@coade.com.
PD 5500 is very conservative. One of the major problems is the fact that the pressure stress which is the hoop stress multiplied by the stress concentration factor (scf) is added to the membrane componen differently from the way it is done in WRC107. In effect, this pressure stress gets added twice. Also, you will notice that in WRC107 there are a number of blanks in their table, and PD5500 fills in all the blanks.
To see which load is causing the major problem,you could try and see what happens when the pressure is reduced to zero. Also, the circumferential moment can cause a problem.
In Annex W of PD 5500, there is a sample calculation of a nozzle with a re-pad installed in a cylindrical shell, and you will see there how the stress components are added.