Code Case for Extension Use of 2-1/4Cr-1Mo-1/4V Steels for Vessels in ASME Section VIII Division 3

2-1/4Cr-1Mo-1/4V steels have been used extensively as materials for reactors in high temperature and high pressure hydrogeneration service. The design temperature of these reactors is 850F to 900F. These reactors have been designed per ASME Sec. VIII Division 2. If these reactors can be designed per ASME Sec. VIII Division 3, thickness of shell and head for these reactors in case of design temperature of 850F can be reduced by about 15% compared with that per Division 2 even if the membrane abjustment factors based on creep allowable stress are applied. However yield strength in Division 3 is limited less than 700F. In this paper, the additional requirements and background for extension use of 2-1/4Cr-1Mo-1/4V steels are presented.