Tolerance Consideration in Cylindrical Shell Thickness as per Div 1 2

[SmallInfo]

Hi Experts!
I am designing a pressure vessel using PV Elite software which generated this report

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

 

[david339933]

You need to know this if you are designing pressure vessels. Are you qualified per App. 47?

 

[SmallInfo]

david339933
Thanks for your reply, practicing to design in future.

 

[GBTorpenhow]

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).

 

[SmallInfo]

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?

 

[GBTorpenhow]

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.

 

[r6155]

You are using an old 2017 edition.
This is not a game.

Regards

 

[david339933]

See UG-16.

 

[Geoff13]

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%.