Small openings UG-36 (c) (3) (a) 2

[AMenJr]

How do you folks define "required minimum thickness of 3/8" or less" for 3-1/2" or less finished openings? Does this mean the "nominal" or "computed" thickness of the shell? I believe it means the computed thickness. (Example: If the shell nominal thickness is 1/2" plate and the computed is .299", a 3" (3-1/2" OD) pipe nozzle does not require reinforcement other that that inherent in the construction, provided no rapid fluctuations in pressure exist.). I'm sure this is an elementary question to somebody out there who has dealt with this already in the past.

 

[jte]

AMen-

When all else fails, read the definitions!

From Appendix 3:

thickness of vessel wall
(a) design thickness — the sum of the required
thickness and the corrosion allowance (see UG-25)
(b) required thickness — that computed by the formulas
in this Division before corrosion allowance is added
(see UG-22)
(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.

See also UG-27(a) and (b).

jt

 

[LSThill]

Here is a link to a pdf by Randall W. Whiteside. P.E. that has a pictorial explanation of this rule.

http://www.pdhonline.org/courses/m205/m205content.pdf

 

[AMenJr]

Summarizing all of my findings:
I looked closer at the code concerning UG-36 (c) (3) (a) on pages 38 & 39 and as per the Eng-Tips replies.

The definition of "required minimum thickness of 3/8" is the minimum thickness required in the corroded condition.

I am basing this definition on UG-16 (e) page 13, UG-27 (b) t definition on page 18 and Appendix 3 definition of "thickness of vessel wall" (b) on page 367. In addition, I have the 1950 ASME Code and it states "3/8" or less wall thickness" on page 42 in UG-36 (c) (2). There has obviously been a change in verbage from 1950 to 2004, and it is clear that they changed to the "required minimum thickness of 3/8".

I would like to especially thank jte and lsthill for their insite and shedding light on this issue. I want you to know that this small clarification has helped me apply the calculation properly for this vessel, concerning 3" and smaller openings, and it has helped influenced my supervisors opinion of my ASME Code abilities. I am appreciative of this from both you and Eng-Tips. I would like to confer a medal of respect for this site .