ASME Material Stress Historical References 1

[ReliabilityGuy90]

Hi

Ive been doing work for our client in the refining industry and have been lots of BPVC analyses on the vessels in the field, mainly revolving around their build thicknesses.

I mainly work with vessels built to ASME Section VIII-I which references material properties from Section II Part D. The problem Im having is finding the proper stress values for the older equipment. The calculation software packages the client works with is limited to only so many revisions of specs, yet they want us to analyse this vessel in a manner to which it was built.

Does anyone know of a good resource for finding old historical codes and standards of Material Properties? This would make my life much easier if so!

-RG90

 

[jte]

Well, most commercial software packages have a 1995 option. For Div. 1 vessels, that handles the vessels built to the "old" design margins of 4 against UTS and 2/3 yield, and fatigue and creep. The modern design margins were implemented with the 1998 edition 1999 addenda, so I suspect that the software vendors chose 1995 edition primarily to avoid confusion with "edition" vs. "addenda" years. This will be good back to 1968 when the first Div. 1 was issued. Prior to 1968 there were no divisions, just Section VIII. Now, if you have vessels older than 1968 (really older than 1960's) you need to start to be careful, since the design margins changed around a bit pre- World War II, during the war years, post-war, etc. One also has to pay attention during that era to ASME or API-ASME vessel codes.

But I suspect that most of your work will relate to post 1968 vessels, so you should be fine using the 1995 edition.

 

[ReliabilityGuy90]

Thanks for the response JTE,

Yes the package has a 1995 edition for this particular material, but varies in its dates for other materials depending on the type.

This project is in its initial implementation so we're still trying to decipher much of the code but here's the reoccurring predicament:

Ex) I get a vessel with a U1 doc saying its built at a specific date, lets say 1981, and its got a Ellipsoidal head made of 0.187" of SA-240-304L and designed at 150F. When I go to run a minimum thickness calc using properties of the 1995 code, the minimum thickness exceeds what its actually built at.

This prompted me to look at an older edition of Section II from 1992 which yielded a higher Allowable Stress at the same temp, which puts me in the green. I have a handful of vessels like this which makes me think that the stresses are not actually consistent from '68-'98 and if I could get my hands on these codes then Id be out of the dark.

 

[SnTMan]

As I recall, stresses for stainless materials were often changed by fairly small amounts across the Edition / Addenda.

ReliabilityGuy90, it'd be good if you could get the Sec II, Part D for the years your vessels were built. Unfortunately I don't know where to suggest you can get them.

Regards,

Mike

On Edit: See this: thread794-414686

 

[ReliabilityGuy90]

Thanks for the link SnTMan, Ill be checking that out

 

[jte]

Keep in mind that Section II Part D did not come into existence until the 1992 edition. Prior to that, the allowable stresses were listed directly in VIII Div. 1. So it would be somewhat difficult to find a 1980 Section II Part D.

Now, for the example given by ReliabilityGuy90, specifically SA-240 304L at 150°F, the Spring 1982 addenda to the 1980 edition Table UHA-23 shows a max. allowable stress in tension of 15.7 ksi thru 200°F with note 1 which is the familiar "where slightly greater deformation is acceptable". In other words, this is the "high stress" variety.

The un-noted version (the "low stress" variety) of SA-240 304L has an allowable stress of 15.7 ksi up to 100°F, dropping to 13.4 ksi at 200°F. As SnTMan points out, values changed, and this particular line is noted as having changed with this addenda (Spring '82). Having said that, a quick comparison with the 1977 ed. Spring '79 addenda does not show any change... Maybe I'm missing something, or perhaps something changed and then was changed back.

I suspect that the issue you are facing may be due to using the high stress version in calculating the head thickness during the original design (in my opinion a valid decision), while your current check may be using the low stress value.

 

[ReliabilityGuy90]

JTE thats great news actually. I had done some digging through my clients Codes & Standards database where we found the VIII-I spec for that year available but were perplexed when we couldnt find the II spec. We'll see if we can get our hands on that spec and get this ball rolling.

Thanks for the tips, this will definitely get us moving in the right direction