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Tolerance Consideration in Cylindrical Shell Thickness as per Div 1 2

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SmallInfo

Petroleum
Oct 30, 2017
104
Hi Experts!
I am designing a pressure vessel using PV Elite software which generated this report
post_kqelsk.jpg

Kindly help me understand following things:
a) Is it mandatory to consider tolerance in cyclindrical shell thickness as per div 1?
b) From where this “tu” equation is taken? I don’t find it in div 1 or I am missing something.
c) What is “tn, min” when “tn” is provided and from where this equation is taken?

Thanks in advance
 
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You need to know this if you are designing pressure vessels. Are you qualified per App. 47?
 
david339933
Thanks for your reply, practicing to design in future.
 
If Ca = 0.125" and Tol% = 87.5%:
Lets say I need 0.197" (t) wall after corrosion, then I need 0.322" before corrosion (t+Ca), so I need to order 0.368" or larger (t_n,min). I order 0.375" (t_n) so I am sure to receive at least 0.328" (t_n * Tol%) which would then corrode at worst to 0.203" (t_u).
 
GBTorpenhow
Thank you so much to explain it in very simple way. Can you please guide if these calculations specified in div 1 or we calculate it ourselves to get required thickness?
 
I cannot comment on if or where these are defined in Div. 1 as I am no pressure vessel design expert but these equations are a basic part of any pressure thickness design/selection method subject to both mill tolerance and corrosion allowance.
 
You are using an old 2017 edition.
This is not a game.

Regards
 
UG-16(c) addresses plate under tolerance. Generally it doesn't have to be added as most plate specs follow the 0.01 inch (0.3 mm) rule. For example see SA-20 Table A1.1 Note 1. This is why there is no under tolerance in the calculation for your SA516-70.

UG-16(d) addresses pipe under tolerance. Generally it must be added since the manufacturing under tolerance is very large. Typically 12.5%.
 
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