Richard, thanks for the tip.)
We have a problem like this:
http://65.57.255.42/ubbthreads/ubbthread...=true#Post40883

but just the opposite.
Prospective vendors provide only what is in the ASME.
I would like to find a reference to the properties of the P91, but there is also a problem in the translation of terms from English to Russian and back. I think the reason why the supplier did not understand what we want from him).
And of course I've used Google)))
In such a situation is easier to do calculations on the strength of ASME. But then there is a problem with responsibility limit for the calculations.