What is the current Industry position on the use of 1 1/4 Cr alloy steels w.r.t. crrep embrittlement. Is there a temperature limit above which the switch to 2 1/4 Cr material is recomended?

I would like to add my two cents worth....... Recently, my company has investigated the replacement of 45 year old auxiliary steam piping (ASTM A335 P11 and P22) in a western Pennslyvania power plant. The system was part of a "steam desuperheating station" (a system subject to temperature transients and vibration....) EPRI (the electric power research institute) has published papers and guidelines about the long term failures ( read "creep") of large diameter P11 piping with axial welded seams....... In the late 1980's a "hot-reheat" piping system failed and destroyed the occupied plant lunchroom . After this accident, many older power plants replaced both thier P11 main-steam and hot reheat systems with P22 ASTM A335 P11 ( 1-1/4 Cr) and ASTM A335 P22 (2-1/4 Cr) piping materials were very close to the same price........ we used P22 throughout the system...... and never looked back. I understand that the latest edition of the ASME B31.1 power piping code contains cautions about the use of P11 piping..... There has always been only a limited temperature range of use permitted by this code. In my opinion, I see no reason to ever use or specify P11 piping materials..... Any other references by others is welcome... MJC