Stress corrosion cracking (SCC), hydrogen embrittlement cracking (HEC) and hydrogen induced cracking (HIC) are potential threats to the integrity of materials exposed to sour conditions. Approaches are reviewed for the assessment of limiting operating conditions with respect to SCC, HEC, and HIC and for the fitness for further operation of systems containing SCC and HEC defects. Guidelines for SCC/HEC test method selection for homogeneous materials and materials containing hard zones and for HIC test environment selection are reviewed. The method for the selection of appropriate SCC and HEC tests is based on slow strain rate testing (SSRT). The SSRT is also used to determine conditions at which materials are not susceptible to SCC and HEC and hence to establish limiting operation conditions. The fitness for further service of SCC/HEC defect-containing components is obtained from; i) crack growth rates and maximum allowable defect sizes and/or, ii) a comparison of actual - and threshold stresses, actual - and threshold stress intensity factors and actual - and threshold crack tip opening displacements, determined under the relevant environmental conditions. For materials of existing equipment the limiting environmental conditions for HIC are derived from the threshold hydrogen concentration to initiate hydrogen damage. An approach to estimate this threshold from the inclusion size is discussed.
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