Dabasis: The change in the allowable stress values result from ASME decreasing the safety factor in tensile stress from 025 of TS to 0.33 of TS. I'm not certain why the change, except for perhaps a recognition of better steelmaking and more consistency in mechanical properties than in earlier times. Hope this helps! David Hendrix The Hendrix Group Inc.

Debasis MJC had rightly pointed out that you should go by latest ASME code case amendments - which ASME publishes periodically on specific amenments and also a compiled verson of Code case amendments each year. Allowables stresses and Safety Factor do undergo changes and this is reflected in latest ASME code case amendmens periodically. However if you do not have the latest ASME code case amendment copies and still prefer or wish to follow the old ASME case book copies of 1995, available with you, you have to apply or follow the known allowable stresses and safety factor values, known to you, for SA 516 Gr 70 for your qualification needs . Trust this is of help to you C.V.Srinivasan Nishi Engineers Pvt Ltd India Feb 13, 2006 E-mail:nishi@vsnl.com >Debasis.... > >Here is my two cents worth.... > >Your question brings up a topic that has been discussed >repeated in ASME Code seminars and meetings. > >When specifying, designing, inspecting or testing an ASME >pressure vessel, you must use all of the ALL OF THE RULES in >the code edition of record. > >Since there was a significant change in the safety factor >used for strength calculations, there was also a change in >the allowable stresses. There may be other changes in >material selection or inspection requirements that are part >of that Code edition. > >You must use and understand all of the current Code >changes.....and certainly not pick out the selected rules or >allowable stresses that would favor a requalification of >your existing system........as attractive as that may appear >at times. > >Let us know more about what you are trying to do... > > >-MJC