ASME SEC II, ALLOWABLE STRESS VALUE, HELP!!!!!!!!!

[falco]

Hi To all of you, Does anybody Knows The allowable Strees of High Alloy steel plate 18%Cr9%Ni type 304 at 500 F, according to ASME Sec. II part D. I need this data to evaluate the severity of measures in a thickness measurement inspection on pressure vessel. I only have sec. V and Sec VIII div 1, and I still haven´t found in my country an institution that posess sec II. If somebody Nkow it please write to me to falco@citt.cdb.edu.sv or to rfalconio@hotmail.com

I will realy appreciate your help

Roberto Falconio
NDT & CORROSION TESTING

 

[prex]

12900 psi.
In the site below, if you go to any of the ASME VIII sheets (under 'vessels'), you can choose a material and get the allowable stress.
prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[John3p]

Falco,

I do not find a listing for 18% Cr 9% Ni in the tables. However, there is a listing for 18% Cr 8% Ni Type 304 Steel Plate: Max. Allowable Stress @ 500°F = 12.9 ksi

A well defined problem is half solved.

 

[tom123]

I suppose both of you are chosing SA-240 TP304, line 24. Why are there two lines for the same steel with different Stress Values (line 25 S=17.5 ksi)
Which is the difference?

 

[John3p]

Tom,

I believe Appendix 1 of II-D provides the explanation for the two different stress values. A well defined problem is half solved.

 

[kstaylor]

Falco, be careful in choosing the allowable stress for your material. The ASME recently changed the "design factor" (factor of safety) from 4.0 to 3.5, raising the allowable stress for most materials for temperatures outside the creep zone. Your local jurisdiction may or may not accept use of these higher allowable stresses when evaluating equipment designed to earlier editions of the Code with the 4.0 safety factor. I know for a fact that California has only allowed the new allowable stresses for new equipment, not on rerates or alterations to older equipment.

Tom123, read the notes associated with each line. I believe you will find the higher allowable stresses are not recommended for components that need to seal a fluid and might deform under load (like flanges or threaded connections).