Goodmorning.
We are preparing the documentation to obtain U-Stamp.
The units of our Asme Code are SI, so the stress is in MPa;
Our software (Coade PVElite 2008) has the data base in PSI;
The conversion of the stress from PSI to MPa made by software, gives different values from code;
This fact is due to different rounding.
Do you think that this fact could be a problem during the rewiew?

For example: SA 333 Gr.6
STRESS:
PVElite gives 117.9 MPa;
ASME code in SI gives 118 MPa

An interesting issue that may cause pitfalls for designers. In the 2004 Edition of ASME Code new rules were presented for design of vessels in metric units. An entirely new edition of Section II Part D for allowable stresses in metric was published. Section VIII itself has constant values in US Customary units and metric units. All of these metric values (the constants and the values in II-D) have been rounded so as provide "convenient" working values in the metric systems (SI, MKS, etc). See paragraph U-4 in Section VIII Div 1 for general discussion. There are some relevant appendices as well in Div 1 and in II-D. In general, you can't "mix and match" the units, you must use consistent units for design of any particular component.

I posted a discussion of this issue in another forum (http://www.eng-tips.com/viewthread.cfm?qid=166510). I believe that Michael from TUV has posted on this (TUV) forum as well regarding similar questions.

Some Authorized Inspectors will be very much "sticklers" for this issue of using correct rounding, etc., as well they should.