PD 5500 - Max Nozzle Size on Vessel

Question

PD 5500 - Max Nozzle Size on Vessel

hockchong (Mechanical)

(OP)

9 Mar 04 22:20

Hi,
I have a case here.
Design Code PD 5500 Cat. 1
Design Press = 271 barg
ID = 1000mm
T/T = 3600mm
Thickness = 85mm

There problem is I have a 24" manway. From my calculation, the required nozzle thickness for reinforcement is 250mm. OD of the nozzle is 1110mm and the OD of the vessel is 1170mm. The sofware (PVElite) give an error message. What I need now is a clause in PD 5500 code book that stated that this size is violating the code so that I can convince them to change the size of the nozzle.

I really need answer urgently. Can somebody plaese let me know. Thanks a lot in advance.

Regards,
Lee

prex (Structural) · Answer 1 · 2004-03-10 02:27:02

I have an old BS5500 copy: if D/T_a≤200 as in your case, there is no limit on the permissible diameter of a flush nozzle (if not flush the limit would be one third of D,mean shell diameter).
Sorry for not being able to help you in your goal, as I agree that your situation is an odd one.
As I hope the nozzle is inserted through the shell, I can't see how the weld is designed, as the OD of nozzle is higher than the ID of shell.

prex

http://www.xcalcs.com
Online tools for structural design

hockchong (Mechanical) · Answer 2 · 2004-03-10 02:38:17

Prex,
Thanks for your reply. Unfortunately, the nozzle is flush and even in the latest PD5500 written that there is no limit on the permissible diameter.
The main problem is my client don't accept my explanation on fabrication problem. Anyway, I still hoping somebody here can give me an answer.

waskillywabbit (Mechanical) · Answer 3 · 2004-03-24 11:53:14

From those conditions I did a quick CodeCalc calculation and it seems that your vessel wall thickness is insufficient for that pressure, unless I missed something, so that could be the source of your error. Also, you might check into updating your software, as I have used CodCalc over the past few years I myself have found several errors in their formulations that were later corrected in later versions.

Brian

hockchong (Mechanical) · Answer 4 · 2004-03-24 20:52:05

Wabbit,
Do you mean that my vessel shell can't stand for 271 barg? I have run the calculation using latest PVElite and it show no problem for other small nozzle. Can you plaese check whether you are considering Cat 1. BTW the c.a. is 3.0mm. Thanks.

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PD 5500 - Max Nozzle Size on Vessel