API TR 934-F PART 1 : 2017

The objective of this study, in support of the API Recommended Practice 934-F (Guidance for Establishing a Minimum Pressurization Temperature (MPT) for Heavy Wall Reactors in High Temperature Hydrogen Service During Startups and Shutdowns), is to establish the technical basis for determining a minimum pressurization temperature necessary to avoid Internal Hydrogen Assisted Cracking (IHAC) of weld metal and base plate of temper embrittled 2¼Cr-1Mo steel in high pressure H2 service. The threshold condition for the onset of subcritical crack propagation; and its dependencies on dissolved hydrogen concentration, temperature, and steel purity/temper embrittlement; are targeted as particularly important to pressure vessel safe operations. A second objective is to improve the underlying data base for fracture mechanics fitness-for-service modeling of IHAC. Both analyses are built on the conservative rising-displacement threshold stress intensity factor for IHAC (KIH).