Design of Reinforcement openings.

[Omuye]

Dear All,

Please i have been studying a book "Guidebook for the design of ASME Section VIII Pressure Vessel" by James R. Farr and Mann H. Jawad.

Reference to the attachment Example 5.1. highlighted in yellow for the calculation of reinforcement openings. After the calculation of the minimum required thickness of the ellipsoidal head, to be 0.733in, they selected the nominal thickness as 0.75in.

how did they arrive at this value?

And also, for the calculation of the required nozzle thickness, after solving to get the value as 0.143in , the nominal thickness selected was 1.125in.

How was this arrived?

this is quite confusing and i need some assistance, how these nominal thickness was selected.

Thanks in advance for your help.

 

[chicopee]

a) In the case that you are studying, you have to understand the nuance between required thickness (Tr) and nomimal thickness (Tn). The nominal thickness is the thickness of the head provided by the manufacturer within some tolerances. Since Tr < Tn you are OK with the design.
b) The required thickness (Tr) is less than the actual nozzle thickness (T) used in this example. The nozzle thickness (T) which appears to be excessive for other reasons not revealed in this example is whatwas commercially available and used in the design. Since Tr < T you are OK with the design.

 

[david339933]

I don't see how .750" would be sufficient for this problem. 10% thinning due to forming would leave .675" min. thickness of the head....below min. required.

 

[r6155]

ASME VIII Div.1 MANDATORY APPENDIX 3 DEFINITIONS:3.2.(c) nominal thickness: except as defined in UW-40(f)
and modified in UW-11(g), the nominal thickness is the thickness selected as commercially available, and supplied to the Manufacturer. For plate material, the nominal thickness shall be, at the Manufacturer’s option, either the thickness shown on
the Material Test Report {or material Certificate of Compliance [UG-93(a)(1)]} before forming, or the measured thickness of the plate at the joint or location under consideration.

Regards
r6155