API 939-A : 1994

1.0 Executive Summary
2.0 Introduction
    2.1 Background
    2.2 Goal
    2.3 Technical Approach
    2.4 Terminology
        2.4.1 Wet H[2]S Cracking Mechanisms
              2.4.1.1 Hydrogen Blistering
              2.4.1.2 Hydrogen Induced Cracking (HIC)
              2.4.1.3 Stress Oriented Hydrogen Induced Cracking
                      (SOHIC)
              2.4.1.4 Sulfide Stress Cracking (SSC)
        2.4.2 Steels
              2.4.2.1 Conventional Steel
              2.4.2.2 Low Sulfur Conventional Steel
              2.4.2.3 "HIC resistant" Steel
              2.4.2.4 Ultra-Low Sulfur Advanced Steels
        2.4.3 General Terminology
              2.4.3.1 Crack Length Ratio (CLR)
              2.4.3.2 Crack Thickness Ratio (CTR)
              2.4.3.3 Crack Sensitivity Ratio (CSR)
              2.4.3.4 Longitudinal-Transverse (LT) Section
              2.4.3.5 Transverse-Longitudinal (TL) Section
3.0 Experimental Procedures
    3.1 Materials Evaluated
    3.2 Specimen Configurations
    3.3 Experimental Overview
        3.3.1 Evaluation of Plate Containing Pre-existing HIC
              Damage
        3.3.2 Evaluation of Plate Containing Hard Welds (HRC
              22-30)
        3.3.3 Evaluation of the Repair of a HIC Damaged
              Vessel
        3.3.4 Simulation of the Cracking Behaviour of Thick
              Plate
        3.3.5 Evaluation of HIC Resistant Plate/I.D. Surface
              Cleaning/Severe Hydrogen Charging Conditions
        3.3.6 Evaluation of Nozzle Attachments/Effect of
              PWHT
        3.3.7 Verification of AE Signature for Hydrogen
              Blistering and SSC
4.0 Results and Discussion
    4.1 Materials Selection
    4.2 Fabrication
    4.3 Inspection
    4.4 Vessel Design and Integrity
5.0 References
Appendix I - Serviceability of HIC Damaged Steel
Appendix II - Serviceability of Hard Welds
Appendix III - Evaluation of Weld Repair/PWHT
Appendix IV - Simulation of Thick Plate Behavior
Appendix V - Environmental Staging/Effect of Cleaning
Appendix VI - Serviceability of Nozzle Attachments and
              PWHT

Specifies various aspects of crack propagation in pressurized process equipment exposed to wet hydrogen sulphide environments. Represents one of several significant industry-wide efforts to study and to better understand this phenomenon.